';^2. DESCRIPTION OF PLATES. 



Plate VII. 



Aphis oenotherae. 



Fig. 209. Spermatogonium. 

 210-21 1. Spermatogonia in prophase of mitosis. 



212. Young spermatocyte of first order. 



213. Spermatocjrtes of first order; conjugation of the chromosomes. 



214. Condensation of chromatin — spermatocytes of first order immedi- 



ately before mitosis. 



215. Equatorial plate of first maturation division. 



216. Same, side view, showing chromosomes double. 

 217-218. Anaphase of same mitosis. 



219. Daughter spermatocytes of second order. 



220. Equatorial plate of second maturation mitosis. 



221. Anaphase of same. 



222. Young spermatid. 



223. Equatorial plate of first polar spindle of winter egg. 



224. Equatorial plate of polar spindle of parthenogenetic egg. 



225. Equatorial plate of segmentation spindle of parthenogenetic egg. 



Sagitta bifiinctata. 



Fig. 226. Resting spermatogonia. 



227. Prophase of spermatogonial mitosis. 



228. Last spermatogonial mitosis, metakinesis. 



229. Anaphase of same, showing synapsis of chromosomes at pole of 



spindle, and element x. 



230. Resting spermatocyte of first order. 



231. Bouquet stage. 



232. Later growth stage. 



233. Prophase of first maturation mitosis, some of the chromosomes split 



longitudinally. 



234. Later stage, chromosomes condensing and element .*■ dividing. 

 235-237. First maturation mitosis. 



238. Division of element x between the two maturation divisions. 



239. Second maturation mitosis. 



240. Anaphase of same, showing the element x more deeply stained than 



the chromosomes. 

 247. Young spermatids ; element x still conspicuous. 



