Naked cells, with kernels, like those represented in Fig. 10 _B_, which are continuously changing, stretching out and drawing in formless, finger-like processes, and which are on this account called amboid, are found frequently and widely dispersed in fresh water and in the sea; nay, are even found creeping on land. They take their food in the same way as was previously described in the case of the Protamba (vol. i. p.

186). Their propagation by division can sometimes be observed. (Fig. 10 _C_, _D_.) I have described the processes in an earlier chapter (vol. i.

p. 187). Many of these formless Ambae have lately been recognized as the early stages of development of other Protista (especially the Myxomycetae), or as the freed cells of lower animals and plants. The colourless blood-cells of animals, for example, those of human blood, cannot be distinguished from Ambae. They, like the latter, can receive solid corpuscles into their interior, as I was the first to show by feeding them with finely divided colouring matters (Gen. Morph. i. 271).

However, other Ambae (like the one given in Fig. 10) seem to be independent "good species," since they propagate themselves unchanged throughout many generations. Besides the real, or _naked_, Ambae (Gymnambae), we also find widely diffused in fresh water _case-bearing_ Ambae (Lepambae), whose naked plasma body is _partially_ protected by a more or less solid sh.e.l.l (Arcella), sometimes even by a case (Difflugia) composed of small stones. Lastly, we frequently find in the body of many lower animals parasitic Ambae (Gregarinae), which, adapting themselves to a parasitic life, have surrounded their plasma-body with a delicate closed membrane.

The simple naked Ambae are, next to the Monera, the most important of all organisms to the whole science of biology, and especially to general genealogy. For it is evident that the Ambae originally arose out of simple Monera (Protambae), by the important process of segregation taking place in their h.o.m.ogeneous viscid body-the differentiation of an inner kernel from the surrounding plasma. By this means the great progress from a simple cytod (without kernel) into a real cell (with kernel) was accomplished (compare Fig. 8 _A_ and Fig. 10 _B_). As some of these cells at an early stage encased themselves by secreting a hardened membrane, they formed the first vegetable cells, while others, remaining naked, developed into the first aggregates of animal cells.

The presence or absence of an encircling hard membrane forms the most important, although by no means the entire, difference of form between animal and vegetable cells. As vegetable cells even at an early stage enclose themselves within their hard, thick, and solid cellular sh.e.l.l, like that of the Ambae in a state of rest (Fig. 10 _A_), they remain more independent and less accessible to the influences of the outer world than are the soft animal cells, which are in most cases naked, or merely covered by a thin pliable membrane. But in consequence of this the vegetable cells cannot combine, as do the animal cells, for the construction of higher and composite fibrous tracts, for example, the nervous and muscular tissues. It is probable that, in the case of the most ancient single-celled organisms, there must have developed at an early stage the very important difference in the animal and vegetable mode of receiving food. The most ancient single-celled animals, being naked cells, could admit solid particles into the interior of their soft bodies, as do the Ambae (Fig. 10 _B_) and the colourless blood-cells; whereas the most ancient single-celled plants encased by their membranes were no longer able to do this, and could admit through it only fluid nutrition (by means of diffusion).

[Ill.u.s.tration: FIG. 11.-A single Whip-swimmer (Euglena striata), greatly magnified. Above a thread-like lashing whip is visible; in the centre the round cellular kernel, with its kernel speck.]

The _Whip-swimmers_ (Flagellata), which we consider as a third cla.s.s of the kingdom Protista, are of no less doubtful nature than the Ambae.

They often show as close and important relations to the vegetable as to the animal kingdom. Some Flagellata at an early stage, when freely moving about, cannot be distinguished from real plants, especially from the spores of many Algae; whereas others are directly allied to real animals, namely, to the fringed Infusoria (Ciliata). The Flagellata are simple cells which live in fresh or salt water, either singly or united in colonies. The characteristic part of their body is a very movable simple or compound whip-like appendage (whip, or flagellum) by means of which they actively swim about in the water. This cla.s.s is divided into two orders. Among the fringed whip-swimmers (Cilioflagellata) there exists, in addition to the long whip, a short fringe of vibrating hairs, which is wanting in the unfringed whip-swimmers (Nudoflagellata). To the former belong the flint-sh.e.l.led yellow Peridinia, which are largely active in causing the phosph.o.r.escence of the sea; to the latter belong the green Euglenae, immense ma.s.ses of which frequently make our ponds in spring quite green.

[Ill.u.s.tration: FIG. 12.-The Norwegian Flimmer-ball (Magosphaera planula) swimming by means of its vibratile fringes, as seen from the surface.]

A very remarkable new form of Protista, which I have named _Flimmer-ball_ (Magosphaera), I discovered only three years ago (in September, 1869), on the Norwegian coast (Fig. 12), and have more accurately described in my Biological Studies(15) (p. 137, Plate V.).

Off the island of Gis-oe, near Bergen, I found swimming about, on the surface of the sea, extremely neat little b.a.l.l.s composed of a number (between thirty and forty) of fringed pear-shaped cells, the pointed ends of which were united in the centre like radii. After a time the ball dissolved. The individual cells swarmed about independently in the water like fringed Infusoria, or Ciliata. These afterwards sank to the bottom, drew their fringes into their bodies, and gradually changed into the form of creeping Ambae (like Fig 10 _B_). These last afterwards encased themselves (as in Fig. 10 _A_), and then divided by repeated halvings into a large number of cells (exactly as in the case of the cleavage of the egg, Fig. 6, vol. i. p. 299). The cells became covered with vibratile hairs, broke through the case enclosing them, and now again swam about in the shape of a fringed ball (Fig. 12). This wonderful organism, which sometimes appears like a simple Amba, sometimes as a single fringed cell, sometimes as a many-celled fringed ball, can evidently be cla.s.sed with none of the other Protista, and must be considered as the representative of a new independent group. As this group stands midway between several Protista, and links them together, it may bear the name of _Mediator_, or _Catallacta_.

[Ill.u.s.tration: FIG. 13.-Labyrinthula macrocystis (much enlarged). Below is a large group of acc.u.mulated cells, one of which, on the left, is separating itself; above are two single cells which are gliding along the threads of the retiform labyrinth which form their "tramways."]

The Protista of the fifth cla.s.s, the _Tram-weavers_, or _Labyrinthuleae_, are of a no less puzzling nature; they were lately discovered by Cienkowski on piles in sea water (Fig. 13). They are spindle-shaped cells, mostly of a yellow-ochre colour, which are sometimes united into a dense ma.s.s, sometimes move about in a very peculiar way. They form, in a manner not yet explained, a retiform frame of entangled threads (compared to a labyrinth), and on the dense filamentous "tramways" of this frame they glide about. From the shape of the cells of the Labyrinthuleae we might consider them as the simplest plants, from their motion as the simplest animals, but in reality they are neither animals nor plants.

[Ill.u.s.tration: FIG. 14.-Navicula hippocampus (greatly magnified). In the middle of the cell the cell-kernel (nucleus) is visible, together with its kernel speck (nucleolus).]

The _Flint-cells_ (Diatomeae), a sixth cla.s.s of Protista, are perhaps the most closely related to the Labyrinthuleae. These primary creatures-which at present are generally considered as plants, although some celebrated naturalists still look upon them as animals-inhabit the sea and fresh waters in immense ma.s.ses, and offer an endless variety of the most elegant forms. They are mostly small microscopic cells, which either live singly (Fig. 14), or united in great numbers, and occur either attached to objects, or glide and creep about in a peculiar manner.

Their soft cell-substance, which is of a characteristic brownish yellow colour, is always enclosed by a solid and hard flinty sh.e.l.l, possessing the neatest and most varied forms. This flinty covering is open to the exterior only by one or two slits, through which the enclosed soft plasma-body communicates with the outer world. The flinty cases are found petrified in ma.s.ses, and many rocks-for example, the Tripoli slate polish, the Swedish mountain meal, etc.,-are in a great measure composed of them.

A seventh cla.s.s of Protista is formed by the remarkable _Slime-moulds_ (Myxomycetes). They were formerly universally considered as plants, as real Fungi, until ten years ago the botanist De Bary, by discovering their ontogeny, proved them to be quite distinct from Fungi, and rather to be akin to the lower animals. The mature body is a roundish bladder, often several inches in size, filled with fine spore-dust and soft flakes (Fig. 15), as in the case of the well-known puff-b.a.l.l.s (Gastromycetes). However, the characteristic cellular threads, or hyphae, of a real fungus do not arise from the germinal corpuscles, or spores, of the Myxomycetes, but merely naked ma.s.ses of plasma, or cells, which at first swim about in the form of Flagellata (Fig. 11), afterwards creep about like the Ambae (Fig. 10 _B_), and finally combine with others of the same kind to form large ma.s.ses of "slime," or "plasmodia."

Out of these, again, there arises, by-and-by, the bladder-shaped fruit-body. Many of my readers probably know one of these plasmodia, the aethalium septic.u.m, which in summer forms a beautiful yellow ma.s.s of soft mucus, often several feet in breadth, known by the name of "tan flowers," and penetrates tan-heaps and tan-beds. At an early stage these slimy, freely-creeping Myxomycetes, which live for the most part in damp forests, upon decaying vegetable substances, bark of trees, etc., are with equal justice or injustice declared by zoologists to be animals, while in the mature, bladder-shaped condition of fructification they are by botanists defined as plants.

[Ill.u.s.tration: FIG. 15.-A stalked fruit-body (spore-bladder, filled with spores) of one of the Myxomycetes (Physarum albipes) not much enlarged.]

The nature of the _Ray-streamers_ (Rhizopoda), the eighth cla.s.s of the kingdom Protista, is equally obscure. These remarkable organisms have peopled the sea from the most ancient times of the organic history of the earth, in an immense variety of forms, sometimes creeping at the bottom of the sea, sometimes swimming on the surface. Only very few live in fresh water (Gromia, Actinosphaerium). Most of them possess solid calcareous or flinty sh.e.l.ls of an extremely beautiful construction, which can be perfectly preserved in a fossil state. They have frequently acc.u.mulated in such huge numbers as to form mountain ma.s.ses, although the single individuals are very small, and often scarcely visible, or completely invisible to the naked eye. A very few attain the diameter of a few lines, or even as much as a couple of inches. The name which the cla.s.s bears is given because thousands of exceedingly fine threads of protoplasm radiate from the entire surface of their naked slimy body; these rays are quasi-feet, or pseudopodia, which branch off like roots (whence the term Rhizopoda, signifying root-footed), unite like nets, and are observed continually to change form, as in the case of the simpler plasmic feet of the Amboidea, or Protoplasts. These ever-changing little pseudo-feet serve both for locomotion and for taking food.

The cla.s.s of the Rhizopoda is divided into three different legions, viz.

the chamber-sh.e.l.ls, or Acyttaria, the sun-animalcules, or Heliozoa, and the basket-sh.e.l.ls, or Radiolaria. The _Chamber-sh.e.l.ls_ (Acyttaria) const.i.tute the first and lowest of these three legions; for the whole of their soft body consists merely of simple mucous or slimy cell-matter, or protoplasm, which has not differentiated into cells. However, in spite of this most primitive nature of body, most of the Acyttaria secrete a solid sh.e.l.l composed of calcareous earth, which presents a great variety of exquisite forms. In the more ancient and more simple Acyttaria this sh.e.l.l is a simple chamber, bell-shaped, tubular, or like the sh.e.l.l of a snail, from the mouth of which a bundle of plasmic threads issues. In contrast to these _single-chambered forms_ (Monothalamia), the _many-chambered forms_ (Polythalamia)-to which the great majority of the Acyttaria belong-possess a house, which is composed in an artistic manner of numerous chambers. These chambers sometimes lie in a row one behind the other, sometimes in concentric circles or spirals, in the form of a ring round a central point, and then frequently one above another in many tiers, like the boxes of an amphitheatre. This formation, for example, is found in the nummulites, whose calcareous sh.e.l.ls, of the size of a lentil, have acc.u.mulated to the number of millions, and form whole mountains on the sh.o.r.es of the Mediterranean. The stones of which some of the Egyptian pyramids are built consist of such nummulitic limestone. In most cases the chambers of the sh.e.l.ls of the Polythalamia are wound round one another in a spiral line. The chambers are connected with one another by pa.s.sages and doors, like rooms of a large palace, and are generally open towards the outside by numerous little windows, out of which the plasmic body can stream or strain forth its little pseudo-feet, or rays of slime, which are always changing form. But in spite of the exceedingly complicated and elegant structure of this calcareous labyrinth, in spite of the endless variety in the structure and the decoration of its numerous chambers, and in spite of the regularity and elegance of their execution, the whole of this artistic palace is found to be the secreted product of a perfectly formless, slimy ma.s.s, devoid of any component parts! Verily, if the whole of the recent anatomy of animal and vegetable textures did not support our theory of plastids, if all its important results did not unanimously corroborate the fact that the whole miracle of vital phenomena and vital forms is traceable to the active agency of the formless alb.u.minous combinations of protoplasm, the Polythalamia alone would secure the triumph of that theory. For we may here at any moment, by means of the microscope, point out the wonderful fact, first established by Dujardin and Max Schulze, that the formless mucus of the soft plasma-body, this true "matter of life," is able to secrete the neatest, most regular, and most complicated structures. This secretive skill is simply a result of _inherited adaptation_, and by it we learn to understand how this same "primaeval slime"-this same protoplasm-can produce in the bodies of animals and plants the most different and most complicated cellular forms.

It is, moreover, a matter of special interest that the most ancient organism, the remains of which are found in a petrified condition, belongs to the Polythalamia. This organism is the "Canadian Life's-dawn"

(_Eozoon canadense_), which has already been mentioned, and which was found a few years ago in the Ottawa formation (in the deepest strata of the Laurentian system), on the Ottawa river in Canada. If we expected to find organic remains at all in these most ancient deposits of the primordial period, we should certainly look for such of the most simple Protista as are covered with a solid sh.e.l.l, and in the organization of which the difference between animal and plant is as yet not indicated.

We know of but few species of the _Sun-animalcules_ (Heliozoa), the second cla.s.s of the Rhizopoda. One species is very frequently found in our fresh waters. It was observed even in the last century by a clergyman in Dantzig, Eichhorn by name, and it has been called after him, Actinosphaerium Eichhornii. To the naked eye it appears as a gelatinous grey globule of mucus, about the size of a pin's head.

Looking at it through the microscope, we see hundreds or thousands of fine mucous threads radiating from the central plasma body, and perceive that the inner layer of its cell-substance is different from the outer layer, which forms a bladder-like membrane. In consequence of its structure, this, the little sun-animalcule, although wanting a sh.e.l.l, really rises above the structureless Acyttaria, and forms the transition from these to the Radiolaria. The genus Cystophrys is of a nature akin to it.

The _Basket-sh.e.l.ls_ (Radiolaria) form the third and last cla.s.s of the Rhizopoda. Their lower forms are closely allied to the Heliozoa and Acyttaria, whereas their higher forms rise far above them. They are essentially distinguished from both by the fact that the central part of their body is composed of many cells, and surrounded by a solid membrane. This closed "central capsule," generally of a globular shape, is covered by a mucous layer of plasma, out of which there radiate on all sides thousands of exceedingly fine threads, the branching and confluent so-called pseudopodia. Between these are scattered numerous yellow cells of unknown function, containing grains of starch. Most Radiolaria are characterized by a highly developed skeleton, which consists of flint, and displays a wonderful richness of the neatest and most curious forms. Sometimes this flinty skeleton forms a simple trellice-work ball (Fig. 16 _s_), sometimes a marvellous system of several concentric trelliced b.a.l.l.s, encased in one another, and connected by radial staves. In most cases delicate spikes, which are frequently branched like a tree, radiate from the surface of the b.a.l.l.s.

In other cases the whole skeleton consists of only one flinty star, and is then generally composed of twenty staves, distributed according to definite mathematical laws, and united in a common central point. The skeletons of other Radiolaria again form symmetrical many-chambered structures, as in the case of the Polythalamia. Perhaps no other group of organisms develop in the formation of their skeletons such an amount of various fundamental forms, such geometrical regularity, and such elegant architecture. Most of the forms as yet discovered, I have given in the atlas accompanying my Monograph of the Radiolaria.(23) Here I shall only give as an example the picture of one of the simplest forms, the _Cyrtidosphaera echinoides_ of Nice. The skeleton in this case consists only of a simple trelliced ball (_s_), with short radial spikes (_a_), which loosely surround the central capsule (_c_). Out of the mucous covering, enclosing the latter, radiate a great number of delicate little pseudopodia (_p_), which are partly drawn back underneath the sh.e.l.l, and fused into a lumpy ma.s.s of mucus. Between these are scattered a number of yellow cells (_l_).

[Ill.u.s.tration: FIG. 16.-Cyrtidosphaera echinoides, 400 times enlarged.

_c._ Globular central capsule. _s._ Basket-work of the perforated flinty sh.e.l.l. _a._ Radial spikes, which radiate from the latter. _p._ The pseudo-feet radiating from the mucous covering surrounding the central capsule. _l._ Yellow globular cells, scattered between the latter, containing grains of starch.]

Most Acyttaria live only at the bottom of the sea, on stones and seaweeds, or creep about in sand and mud by means of their pseudopodia, but most Radiolaria swim on the surface of the sea by means of long pseudopodia extending in all directions. They live together there in immense numbers, but are mostly so small that they have been almost completely overlooked, and have only become accurately known during the last fourteen years. Certain Radiolaria living in communities (Polycyttaria) form gelatinous lumps of some lines in diameter. On the other hand, most of those living isolated (Monocyttaria) are invisible to the naked eye; but still their petrified sh.e.l.ls are found acc.u.mulated in such ma.s.ses that in many places they form entire mountains; for example, the Nicobar Islands in the Indian Archipelago, and the Island of Barbadoes in the Antilles.

As most readers are probably but little acquainted with the eight cla.s.ses of the Protista just mentioned, I shall now add some further general observations on their natural history. The great majority of all Protista live in the sea, some swimming freely on the surface, some creeping at the bottom, and others attached to stones, sh.e.l.ls, plants, etc. Many species of Protista also live in fresh water, but only a very small number on dry land (for example, Myxomycetes and some Protoplasta). Most of them can be seen only through the microscope, except when millions of individuals are found acc.u.mulated. Only a few of them attain a diameter of some lines, or as much as an inch. What they lack in size of body they make up for by producing astonishing numbers of individuals, and they very considerably influence in this way the economy of nature. The imperishable remains of dead Protista, for instance, the flinty sh.e.l.ls of the Diatomeae and Radiolaria and the calcareous sh.e.l.ls of the Acyttaria, often form large rock ma.s.ses.

In regard to their _vital phenomena_, especially those of nutrition and propagation, some Protista are more allied to plants, others more to animals. Both in their mode of taking food and in the chemical changes of their living substance, they sometimes more resemble the lower animals, at others the lower plants. _Free locomotion_ is possessed by many Protista, while others are without it; but this does not const.i.tute a characteristic distinction, as we know of undoubted animals which entirely lack free locomotion, and of genuine plants which possess it.

All Protista have a _soul_-that is to say, are "animate"-as well as all animals and all plants. The soul's activity in the Protista manifests itself in their _irritability_, that is, in the movements and other changes which take place in consequence of mechanical, electrical, and chemical irritation of their contractile protoplasm. Consciousness and the capability of will and thought are probably wanting in all Protista.

However, the same qualities are in the same degree also wanting in many of the lower animals, whereas many of the higher animals in these respects are scarcely inferior to the lower races of human beings. In the Protista, as in all other organisms, the activities of the soul are traceable to molecular motions in the protoplasm.

The most important _physiological characteristic_ of the kingdom Protista lies in the exclusively _non-s.e.xual propagation_ of all the organisms belonging to it. The higher animals and plants multiply almost exclusively in a s.e.xual manner. The lower animals and plants multiply also, in many cases, in a non-s.e.xual manner, by division, the formation of buds, the formation of germs, etc. But s.e.xual propagation almost always exists by the side of it, and often regularly alternates with it in succeeding generations (Metagenesis, vol. i. p. 206). All Protista, on the other hand, propagate themselves exclusively in a non-s.e.xual manner, and in fact, the distinction of the two s.e.xes among them has not been effected-there are neither male nor female Protista.

The Protista in regard to their vital phenomena stand midway between animals and plants, that is to say, between their lowest forms; and the same must be said in regard to the _chemical composition_ of their bodies. One of the most important distinctions between the chemical composition of animal and vegetable bodies consists in the characteristic formation of the skeleton. The skeleton, or the solid scaffolding of the body in most genuine plants, consists of a substance called cellulose, devoid of nitrogen, but secreted by the nitrogenous cell-substance, or protoplasm. In most genuine animals, on the other hand, the skeleton generally consists either of nitrogenous combinations (chitin, etc.) or of calcareous earth. In this respect some Protista are more like plants, others more like animals. In many of them the skeleton is princ.i.p.ally or entirely formed of calcareous earth, which is met with both in animal and vegetable bodies. But the active vital substance in all cases is the mucous protoplasm.

In regard to the _form_ of the Protista, it is to be remarked that the _individuality_ of their body almost always remains at an extremely low stage of development. Very many Protista remain for life simple plastids or individuals of the first order. Others, indeed, form colonies or republics of plastids by the union of several individuals. But even these higher individuals of the second order, formed by the combination of simple plastids, for the most part remain at a very low stage of development. The members of such communities among the Protista remain very similar one to another, and never, or only in a slight degree, commence a division of labour, and are consequently as little able to render their community fit for higher functions as are, for example, the savages of Australia. The community of the plastids remains in most cases very loose, and each single plastid retains in a great measure its own individual independence.

A second structural characteristic, which next to their low stage of individuality especially distinguishes the Protista, is the low stage of development of their stereometrical fundamental forms. As I have shown in my theory of fundamental forms (in the fourth book of the General Morphology), a definite geometrical fundamental form can be pointed out in most organisms, both in the general form of the body and in the form of the individual parts. This ideal fundamental form, or type, which is determined by the number, position, combination, and differentiation of the component parts, stands in just the same relation to the _real_ organic form as the ideal geometrical fundamental form of crystals does to their imperfect _real_ form. In most bodies and parts of the bodies of animals and plants this fundamental form is a pyramid. It is a regular pyramid in the so-called "regular radiate" forms, and an irregular pyramid in the more highly differentiated, so-called "bilaterally symmetrical" forms. (Compare the plates in the first volume of my General Morphology, pp. 556-558.) Among the Protista this pyramidal type, which prevails in the animal and vegetable kingdom, is on the whole rare, and instead of it we have either quite irregular (amorphous) or more simple, regular geometrical types; especially frequent are the sphere, the cylinder, the ellipsoid, the spheroid, the double cone, the cone, the regular polygon (tetrahedron, hexahedron, octahedron, dodecahedron, icosahedron), etc. All the fundamental forms of the pro-morphological system, which are of a low rank in that system, prevail in the Protista. However, in many Protista there occur also the higher, regular, and bilateral types, fundamental forms which predominate in the animal and vegetable kingdoms. In this respect some of the Protista are frequently more closely allied to animals (as the Acyttaria), others more so to plants (as the Radiolaria).

With regard to the _palaeontological development of the kingdom Protista_, we may form various, but necessarily very unsafe, genealogical hypotheses. Perhaps the individual cla.s.ses of the kingdom are independent tribes, or phyla, which have developed independently of one another and independently of the animal and the vegetable kingdoms.

Even if we adopt the monophyletic hypothesis of descent, and maintain a common origin from a single form of Moneron for all organisms, without exception, which ever have lived and still live upon the earth, even in this case the connection of the neutral Protista on the one hand with the vegetable kingdom, and on the other hand with the animal kingdom, must be considered as very vague. We must regard them (compare p. 74) as lower off-shoots which have developed directly out of the root of the great double-branched organic pedigree, or perhaps out of the lowest tribe of Protista, which may be supposed to have shot up midway between the two diverging high and vigorous trunks of the animal and vegetable kingdoms. The individual cla.s.ses of the Protista, whether they are more closely connected at their roots in groups, or only form a loose bunch of root offsets, must in this case be regarded as having nothing to do either with the diverging groups of organisms belonging to the animal kingdom on the right, or to the vegetable kingdom on the left. They must be supposed to have retained the original simple character of the common primaeval living thing more than have genuine animals and genuine plants.

But if we adopt the polyphyletic hypothesis of descent, we have to imagine a number of organic tribes, or phyla, which all shoot up by spontaneous generation out of the same ground, by the side of and independent of one another. (Compare p. 75.) In that case numbers of different Monera must have arisen by spontaneous generation whose differences would depend only upon slight, to us imperceptible, differences in their chemical composition, and consequently upon differences in their capability of development. A small number of Monera would then have given origin to the animal kingdom, and, again, a small number would have produced the vegetable kingdom. Between these two groups, however, there would have developed, independently of them, a large number of independent tribes, which have remained at a lower stage of organization, and which have neither developed into genuine plants nor into genuine animals.

A safe means of deciding between the monophyletic and polyphyletic hypotheses is as yet quite impossible, considering the imperfect state of our phylogenetic knowledge. The different groups of Protista, and those lowest forms of the animal kingdom and of the vegetable kingdom which are scarcely distinguishable from the Protista, show such a close connection with one another and such a confused mixture of characteristics, that at present any systematic division and arrangement of the groups of forms seem more or less artificial and forced. Hence the attempt here offered must be regarded as entirely provisional. But the more deeply we penetrate into the genealogical secrets of this obscure domain of inquiry, the more probable appears the idea that the vegetable kingdom and the animal kingdom are each of independent origin, and that midway between these two great pedigrees a number of other independent small groups of organisms have arisen by repeated acts of spontaneous generation, which on account of their indifferent neutral character, and in consequence of their mixture of animal and vegetable properties, may lay claim to the designation of independent Protista.

II. III.

=Vegetable Kingdom= =Animal Kingdom= Plantae _Animalia_ /--------^---------- /-------------------------------^------------ Flowering Plants Vertebrate Animals _Phanerogamia_ _Vertebrata_ | -----v-------/ | | | | | Articulated Animals | | _Arthropoda_ | | -----v------/ | | | | | | | | Star-fishes | | Molluscous Animals Ferns _Echinoderma_ | | _Mollusca_ _Filicinae_ -----v------/ | | -----v------/ | | | | | | | | | | | | | | | | | | | | Mosses -------------------v---------------/ _Muscinae_ Lichens Worms | _Lichenes_ _Vermes_ | | | | | | | | Animal-trees | | | _Zoophytes_ | -- Fungi | | _Algae_ _Fungi_ | | | | | | | | | | -------v-----/ -----v---/ =Neutral= =Primaeval Plants= =Primaeval Creatures= =Primaeval Animals= Protophyta Protista Protozoa -----v------/ -----v------/ -----v------/

||| ||||||||||| ||||| ||| ||||||||||| ||||| ||| ||||||||||| ||||| Vegetable Monera Neutral Monera Animal Monera | ||||| | | ||||| | | ||||| | --------------------------v------------/

| | =Archigonic Monera=

(Pieces of Protoplasm which have originated by Spontaneous Generation)

POLYPHYLETIC PEDIGREE.

II. I. III.

=Vegetable= =Protista= =Animal= =Kingdom= =Kingdom= =Kingdom= Vegetabilia Protista Animalia ------v------/ | -----v----/ | | | | | | | /-----------------------------------^-------------------------------- | | Slime-moulds, | | or | | Mucous Fungi Ray-streamers | | _Myxomycetes_ _Rhizopoda_ | | -----v------/ -----v------/ | | | | | | | Flint-cells | Flimmer-b.a.l.l.s | | | _Diatomae_ | _Catallacta_ | | | -----v------/ | -----v------/ | | | | | | | | | | Whip-swimmers | | | | | | _Flagellata_ | | | | | | -----v------/ | | | | | | | | | | | | | Tram-weavers | | | | | | | _Labyrinthulea_ | | | | | | | -----v------/ | | | | | | | | | | | | | | | | Ambae, | | | =Primaeval= =Primaeval Plants= | | | or | | | =Animals= Protophyta | | | Protoplasta | | | Protozoa ------v------/ | | | -----v------/ | | | -----v------/ ||| | | | ||||| | | | ||||||| ||| | | | ||||| | | | ||||||| ||| | | | ||||| | | | ||||||| ||| | | | ||||| | | | ||||||| =Vegetable= | | | =Neutral= | | | =Animal= =Monera= | | | =Monera= | | | =Monera= | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | || | | || | | || | | | || | | | || | | | || | |||| | ||| | | || ||| | || | || | | | || | || | ||| | ||||| | |||| | ||| ||||| | |||| | ||| | ||| | ||| | ||| | ||| | ||||| | |||| | ||||| ||||| | |||| | ||| | ||| | ||| | ||| | ||| | ||||| | |||| | ||||| -------------------------------------------------------------------------------------------

N.B.-The lines marked with a indicate extinct tribes of Protista, which have arisen independently by repeated acts of Spontaneous Generation.

Thus, if we a.s.sume one entirely independent trunk for the vegetable kingdom, and a second for the animal kingdom, we may set up a number of independent stems of Protista, each of which has developed, quite independently of other stems and trunks, from a special archigonic form of Monera. In order to make this relation more clear, we may imagine the whole world of organisms as an immense meadow which is partially withered, and upon which two many-branched and mighty trees are standing, likewise partially withered. The two great trees represent the animal and vegetable kingdoms, their fresh and still green branches the living animals and plants; the dead branches with withered leaves represent the extinct groups. The withered gra.s.s of the meadow corresponds to the numerous extinct tribes, and the few stalks, still green, to the still living phyla of the kingdom Protista. But the common soil of the meadow, from which all have sprung up, is primaeval by protoplasm.