CHANGES IN THE OVARY 117 



together in tlie form of a lump, or dark mass, heaped up at one side 

 of the nuclear region, (r) Pachytenic stage.— The nuclear filaments 

 again heconie unwound, and spread tliemsel\'es out over the whole 

 nuclear region; they are, liowever, consideralily coarser than in the 

 earlier stages. (</) Diplotenic stage.— The chromatin strands split 



V..^1 \ 



■^.iilil'^^.JJigiaiie*-' 



Pachytenic stage. 

 Fio. .31. — Developing ova fi'om ovary one day after birth. (After Lane-Clay]5on.) 



along their whole length, and tlie two halves of each strand at lirst 

 lie in ]jairs near to one another, (cj iJictyate stage. — The split 

 strands pass away fr(jm one another, and the chromatin generally 







Diplotenic nucleus three days 

 aftei' liirtli. 



Dictvate nucleus se\en days 

 after birth. 



Fig. 



-Developing ova. (After Lane-CIaypon.) 



becomes distributed once more throughout the nuclear region in the 

 form of a reticulum. 



The nucleus or gernrinal vesicle of tlie primordial ovum thus 

 produced then enters upon a long period of rest, the changes 

 involved in 0(igenesis having been completed. ^ 



' For an account of the minute structure of the Mananaliaii egg, together 

 with a ivsuniu of the liteiature, see van dei' Stricht, " La Structuie de FCEuf 

 des Mammift-res," Part I., Arrh. de Biol., vol. xxi., 1904; Part IT., Bull, de 

 I'Aciid. lliti/ide de Mi'derine de Ijeli/iqiie, Bruxelles, 190.5; Part IIP, Biuxelles, 



