STUDIES OF REPRODUCTIVE ELEMENTS: T. 13 



a. Thr Formative Zonc. — X^ ahove stated this zone is exaetlv 

 alike in both sacs. The sizes of the germinal cells, their nuclei, and 

 their chi'c.miatic fibres are so alike in the two sexes, that it would be 

 difficult to say whether they belona' to an ovary or to a testis. The 

 oiilv difference between them is that this zone is much shorter in 

 ovarv than in testis, and tliat more karvokinetic cell-divisions a]-e 

 preseiil in tlie latter than in tlu' former. HaecJcer^^' was also not 

 able to see any "^Mitose" in tliis i-co-ion of rlie o\'arv of (7//r'^ryy).s^^ ))iit 

 he does not hesitate io affirm that sucli occurs liere. A comparison 

 of figs. 1 and 2 of the testicular sac with figs. 23 and 24 of tlie ovary 

 will show the resemblance beyond all doubt. 



h. The Onvring Zone. — There appears iii this zone a great 

 difference between the egg- and spermatic-cells, just as in the case of 

 . l.s\vY?'/.s. of wliich Hertwig^^'^^ says : — 



" In diesem zweiten Abschnitt der (reschlectsröhren treten in 

 der Aiiordnung der Eier nnd Samenzellen erliebliche A^erschieden- 

 lieiten hervor. Erstere nehmen an (xrösse ausserordentlich zu und 

 ordnen sicli dal)ei in einfacher Lao-e um eine central o-eleo-ene Rhachis 

 an. Die Samenzellen dagegen, die sich zwar auch, aber in A'ergleich 

 zu den Eiern viel weniger vergrössern, sitzen zahlreichen Rhachis- 

 lamelleii mit Protoplasmafäden auf, " 



This difference lietween the egg- and s|K')-inatic-celIs in Diaiitmints 

 is still greater t^haii in .Iscaris^ where tlie spermatic cells become also 

 loaded with yolk-graniiles like the egg-cells, and gi'ow to two to foni- 

 times their original mass, wliereas in JJiap'nnius tlie growth is 

 very limited. Ihit this difference in size is a ])oint of no great 

 importance in comparison witli tlie much greafer similaiitv existing 

 between these two elements, in tlie c<implete disa])pearance of chro- 

 mosomes and the resting condition of iiuclei in both sexes. Here 

 again occurs a sliglit diffeivnce between the two in regard to the 



