364 THOS. H. MONTGOMERY, 



rig. 152. One bivalent chromosome, same stage. 



Fig. 153. Nucleus of 1st spermatocyte, prophase, showing 7 whole 

 bivalent chromosomes and a portion of an eighth. 



Fig. 154. Idem, showing 2 whole bivalent chromosomes. 



Fig. 155. Idem, „ 9 



Fig. 156. Idem, „ 7 



Fig. 157. Idem, „ 5 



Fig. 158. Idem, „ 9 



Fig. 159. Idem, „ 7 



Fig. 160. Lateral view of 1st spermatocyte, prophase, only one 

 pair of centrosomes drawn ; 2 whole chromosomes and a portion of a 

 third shown. 



Figs. 161 — 165. Lateral views of 1st spermatocytes, late pro- 

 phases, showing successive stages in the separation of the centro- 

 some pairs. 



Plate 22. 



Figs. 166 — 169. 1st spermatocytes, late prophases, successive stages 

 in the separation of the centrosome pairs. 



Fig. 170. 1st spermatocyte, late prophase, showing 7 entii^e bi- 

 valent chromosomes. 



Fig. 171. Idem, 6 whole bivalent chromosomes. 



Fig. 172. Idem, 14 „ 



Fig. 173. Idem, 7 „ 



Fig. 174. Idem, 14 „ 



Figs. 175, 176. 1st spermatocytes, formation of the first maturation 

 spindle. 



Fig. 177. Oblique view of one pole of an early first maturation 

 monaster. 



Fig. 178. 1st spermatocyte, late prophase (after disappearance of 

 the nuclear membrane), showing the 14 bivalent chromosomes in their 

 definitive form ; other details not shown. 



Figs. 179 — 182. Lateral views of 1st maturation monasters. 



Fig. 183. Quadrivalent chromosome from a lateral view of monaster 

 stage of 1st maturation division. 



Fig. 184. 5 bivalent chromosomes, lateral view, monaster of 1st 

 maturation division. 



Fig. 185. 4 bivalent chromosomes, metakinesis, lateral view. 



Fig. 186. 6 bivalent chromosomes, lateral view, commencement of 

 metakinesis of 1st maturation division. 



Figs. 187, 188. Pole views of monaster stages of 1st maturation 

 division, each showing 14 chromosomes. 



Fig. 189. 1st maturation monaster, lateral view of 2 chromosomes. 



Fig. 190. 1st maturation metakinesis, lateral view, showing 3 

 chromosomes and their mantle fibres. 



Figs. 191, 192. Lateral views of chromosomes in metakinesis of 

 the 1st maturation division. 



