THE RELATION BETWEEN AMITOSIS AND MITOSIS. 



terest to note that some of the nuclei in the figure are distinctly 

 hemispherical as if they had been formed in the manner repre- 

 sented in Figs. 30, ^-30, C. 



In Fig. 32 (PI. XIII.) three cavities appear, the old nucleolus 

 being visible in the one on the right. In the middle cavity there 

 are four nuclei. Fig. 33 (PI. XIII.) shows another case in which 

 portions of two nuclear cavities are visible, each with its nucleo- 

 lus, and seven nuclei, four about one cavity, three about the other. 



In Figs. 34, 35 and 36 (PI. XIII.) groups of nuclei are shown 

 lying in cavities of the cytophore : nucleoli were not visible in 

 this section and it was impossible to determine how many sper- 

 matocytes were involved in the formation of these groups. That 

 such groups as these are formed by fragmentation there can, I 

 think, be no doubt. In all cases where the spermatocytes divide 

 mitotically in groups the spindles lie peripherally and nearly 

 tangentially in the cytophore (Figs. 19, 20, 23, PI. XI.; 25, 26, 

 PI. XII.), and the nuclei formed lie at or near the periphery 

 (Figs. 24, PI. XL; 42, 43, 44, PI. XIV.). There are no grounds 

 for supposing that they migrate from the periphery and return 

 to it ; moreover, it is difficult to see how nuclei grouped as those 

 in Figs. 34 and 35 (PI. XIII.) are grouped qould have been formed 

 in situ by mitosis. It seems probable that this difference in posi- 

 tion is quite sufficient to distinguish the nuclei formed by frag- 

 mentation of spermatocytes from those formed by the spermato- 

 genetic mitoses. 



Assuming that these nuclei have arisen by the fragmentation 

 of spermatocytes, the number of chromatin granules has in- 

 creased beyond that contained in some of the nuclei at the time 

 of their formation and the nuclei are now somewhat larger than 

 some of those. No further growth takes place, however. The 

 nuclei themselves are indistinguishable from those spermatid nu- 

 clei which lie at the periphery of the cytophores and are doubt- 

 less the products of mitoses (Figs. 42, 43, PI. XIV.). 



Figs. 37 (PI. XIII.) and 38 (PI. XIV.) represent larger areas 

 of two testes showing how the nuclei which, judging from their 

 position in the cytophore, have arisen by fragmentation are situ- 

 ated in relation to other stages. No trace of definite position or 

 arrangement of the various stages in the testis could be found. 



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