STUDIES OF REPRODUCTIVE ELEMENTS: I. 7 



seen in %s. K), 17, 18, 19, 20, 21, and 22, whicli are drawn from a 

 testis and vas deferens of one and tlie same indi\idi];d nnder tlie same 

 magnifying power. 



2. The Ovarian Sac. 



Tlio ovarv of Diaptoinui^ I examined, consisted of a median 

 unpaired part — the ovarv ])i-oper — and tlie o\idiicts ai-ising on 

 both sides of it. For the sake of eonvenience I haxe divided the 

 contents of the ovary into three different zones as in the case of t1ie 

 testicular sac, although the distinctions are here not so complete -as in 

 the latter : a) the formative zone which occupies the extreme blind end 

 of the sac ; /)) tlie (iroioinfj zone tilling the rest of the whole ovarian sac 

 and part of the oviducts ; and <•) tlie zone of ripening occupying the 

 oviducts alone. In fict the ])rocess of ripening <h)es not end within 

 the l)ody of the animal : the second polar body, as was first observed 

 by Gi'ohhen,^^' is foi-ined after tlie eggs have been laid in the breeding- 

 sac and attached to the base of the tail of a female. The ripening zone 

 moivoxer overhips the hinder part of the second zone. 



a. The Formative Zone. — At the extreme blind end of the ovarian 

 sac, which ends in a very narrow tube C(^ntaining but a single row of 

 germ-cells, we meet with cells quite similar to tliose we find in tlie 

 posterioi- third of a testis. A comparison of figs. 23 and 24 with fig. 2 

 of the testis will at once show this .-huilarity. In these cells of the 

 tjvarian sac, too, a relatively large nucleus contains chromatic nets whicli 

 are certainly in the '' skein " stage, but the karvokinetic figures are \er\- 

 scantily to be seen. Xext follow the cells which to all a])pearance 

 seem to corres])oiid with the testicidar cells as represented in fig. o 

 and whi(h are ;ippareiitl\' in the beginning of a J/,s77//V')/i .s^a^e. The 

 chromatic fibres Ix'come finei" and finei- till thev appear as minute dots 



