553 



all together in one region of the testis, as in the case figured, in 

 other cases only a single nucleus here and there undergoes de- 

 generation. 



Mitoses gradually become more frequent among the nuclei remain- 

 ing, but they are not by any means the only method of division, for 

 some of the nuclei continue to divide amitotically until much later 

 stages. An account of later stages is postponed to another time. 



Those who regard amitosis as necessarily degenerative in nature 

 may conclude that some nuclei have divided mitotically throughout 

 their history, having merely been overlooked, and that the descendants 

 of these are the only ones which give rise to spermatozoa. I cannot 

 see, however, how such an interpretation is possible. If every testis 

 contained at least one mother nucleus which divided only mitotically, 

 cases of this division would surely have appeared in some of the 

 hundreds of testes which I have examined in the earliest distinguishable 

 stages. But no such 



case has been observ- 

 ed. Moreover I have 

 seen many young testes 

 in which every nucleus 

 was dividing amitoti- 

 cally. Finally, no cases 

 of mitosis have been 

 observed in the par- 

 enchyma of earlier 

 stages from which the 

 mother nuclei of the 

 testes arise. At present 

 I can see no escape 

 from the conclusion 

 that the early divisions 

 of the male sexual cells 

 are all amitotic. 



Turning now to the ovaries we find similar conditions obtaining 

 there. The ovaries themselves arise relatively late and in connection 

 with the oviduct and vagina, which together with the vas deferens 

 has differentiated from the mass of dividing nuclei near the longi- 

 tudinal nephridial canals on each side. 



Figure 7 represents a group of ovarian nuclei in the early stages 

 of ovary development. The cases of amitosis are sufficiently numerous 

 and distinct to leave no doubt that this is the characteristic method 



Fig. 6. 



