THE RELATION BETWEEN AMITOSIS AND MITOSIS. 1/7 



I am aware, taken all possible precautions to assure myself that 

 they are, it seems impossible to escape the conclusion that in 

 Moniesia the male germ-cells may develop from cells which 

 have previously been differentiated and functional in the soma. 

 Generalization from this conclusion is, however, no more justi- 

 fiable than is that so often made from observations which seem 

 to point in the opposite direction. It does not seem probable 

 that uniformity exists here any more than in other features of 

 development in regard to which premature generalizations mark 

 like wrecks the dangers along the channel of biological thought. 



In slightly later stages it is difficult or impossible to determine 

 with certainty which testes have arisen from the smaller and 

 which from the larger cells. Figs. 3, A-%, F(P\. VII.), represent 

 young testes which probably developed from the smaller paren- 

 chymal nuclei : amitosis is visible in all cases except Fig. 3, F, in 

 which mitosis is occurring. In the hundreds of testes examined 

 at this stage four cases of mitotic division have been observed of 

 which one is shown in this figure. All of the observed cases 

 were found in a single chain of Moniesia expansa, another fact 

 which seems to indicate that the relative frequency of the two 

 forms of division may vary. It was not possible to determine 

 the number of chromosomes with certainty, but it was more than 

 twelve, the number shown in the figure. 



Figs. 4, A 4, D (PI. VIII.), represent cases which probably de- 

 veloped from the large cells-- muscle cells. Such stages are 

 found in the same proglottids as the stages shown in Figs. 3, 

 A F, and are clearly larger and contain more nuclei than the 

 latter. Fig. 4, A, shows a case in which a small nucleus, appar- 

 ently not a part of the large mass, is also seemingly involved in the 

 development. Cases of this sort are not infrequent, and the 

 small nucleus often becomes one of the membrane-nuclei, though 

 the latter appear in many cases to arise from the same primordium 

 as the germ-cells themselves. Here, as in the development of the 

 female organs, it is difficult to resist the impression that the de- 

 velopment of these organs is the result of some localized stimu- 

 lus or condition and that any cells within reach of this factor may 

 become involved. 



At this stage the nuclei of the developing testis lie in a con- 



