_Ellychnia corrusca_ (_Family Lampyridae_).

236. Equatorial plate of spermatogonium, 19 chromosomes.

[Ill.u.s.tration: STEVENS PLATE XIII.

N. M. S. del.

COLEOPTERA]

PLATE XIV.

_Aphrophora quadrangularis_ (_Hemiptera h.o.m.optera_).

FIG. 237. Resting primary spermatogonium with lobed nucleus.

238. Resting secondary spermatogonium, with nucleus staining much more deeply.

239. Equatorial plate of secondary spermatogonium, 23 chromosomes.

240. First spermatocytes, very early growth stage, _x_ the odd chromosome.

241-243. First spermatocyte, later spireme stages, showing the odd chromosome (_x_) and a pair of _m_-chromosomes (_m_).

244. Similar stage from a safranin-gentian preparation.

245. First spermatocyte, split-spireme stage, _x_ the odd chromosome, _m_ the _m_-chromosome tetrad.

246. Similar stage from a safranin-gentian preparation.

247-248. First spermatocyte, condensation of chromatin granules to form tetrads in the linin spireme.

249. Later tetrad stage.

250-251. First spermatocytes, metaphase from mercuro-nitric material.

252-254. Similar stages from Hermann material, showing longitudinal split in both the bivalents, and the odd chromosome (_x_).

255. First spermatocyte, anaphase.

256. First spermatocyte, telophase.

257. First spermatocyte, daughter plates containing 11 and 12 chromosomes, respectively.

258. First spermatocyte, _a_ and _c_ daughter plates, each containing 11 chromosomes, _x_ the odd chromosome at a different level (_b_).

259. Second spermatocyte, equatorial plates of the two cla.s.ses.

260. Second spermatocyte, metaphase.

261. Second spermatocyte, anaphase.

262-263. Second spermatocyte, daughter plates of the two cla.s.ses.

[Ill.u.s.tration: STEVENS PLATE XIV.

N. M. S. del.

HEMIPTERA h.o.m.oPTERA]

PLATE XV.

_Aphrophora quadrangularis._

FIGS. 264-265. Second spermatocyte, telophase, showing chromatin nucleolus (_n_) and the products of division of the odd chromosome (_x_).

266. A spermatid containing the chromatin nucleolus (_n_).

267-268. Spermatids containing both the chromatin nucleolus (_n_) and the odd chromosome (_x_), _a_ the acrosome.

269. Equatorial plate from a somatic cell of a male larva, 23 chromosomes.

270. Equatorial plate of an oogonium, 24 chromosomes.

271. Resting nucleus of a young oocyte before synapsis, showing two pairs of condensed chromosomes, corresponding in size to the _m_-chromosomes and the odd chromosome of the spermatocytes.

272-277. Sections of nuclei of oocytes, showing one or more of these heterochromosomes, from safranin-gentian preparations.

278-279. Bouquet stage from iron-haematoxylin preparations, showing the heterochromosome bivalent (_x_).

_Cacoecia cerasivorana_ (_Lepidoptera_).

280. First spermatocyte, synizesis stage, showing 2 condensed chromosomes (_x_{1}_ and _x_{2}_).

281-282. First spermatocyte, synapsis stage.

283-284. First spermatocyte, growth stages.

285. First spermatocyte, prophase.

286-287. First spermatocyte, later prophases, showing the heterochromosome pair (_x_).

288. First spermatocyte, metaphase.