THE RELATION BETWEEN AMITOSIS AND MITOSIS. iSl 



the groups that they are merely the result of connection of cells 

 lying near each other. 



The grouping of the cells is not by any means a characteristic 

 feature in these stages. Frequently cells which are entirely 

 separate from each other pass into the spireme stage simultane- 

 ously (Figs. 10, B, n, A, PI. X.). As will appear below, the 

 grouping is merely the first step in a process characteristic of 

 spermatogenesis and observation indicates that in some cells it 

 begins before the spireme appears in others not until later. 



As in the ovary the spireme is usually massed at one side of 

 the nucleus as in many other cases of synapsis and is often visibly 

 connected with the nucleolus (Figs. 12, A-12 B, PI. X.), which, 

 however, does not decrease in size but increases as the nucleus 

 grows larger (Figs. 10, A-1%, B, PI. X.). 



The appearance of the spireme is accompanied by an increase 

 in the amount of cytoplasm. Comparison of the cells in this 

 stage with those in earlier stages in Figs. 10, A, 10, B, and 1 1, A 

 (PI. X.), shows this difference clearly. The cytoplasm in the 

 spireme stages also appears somewhat more dense in structure 

 and stains a little more deeply. Here as in the ovary the ap- 

 parent connection of the nuclear changes with the growth of the 

 cytoplasm is most striking. 



As is usual, this stage in the testes is not accompanied by such 

 extreme growth of the cytoplasm as in the ovary nor by any 

 formation of yolk, but is soon followed by the spermatogenetic 

 divisions. 



But the stages following the spireme are not the same in all 

 cells ; the later development follows two very different lines. In 

 the later stages of the spireme period it is possible to distinguish 

 two different sorts of nuclei. In the one (Fig. 13, A, PI. X.) 

 the nucleolus has disappeared and the spireme is very dense and 

 occupies almost the whole periphery of the nucleus. Careful 

 examination and comparison has convinced me that these nuclei 

 are in preparation for the first spermatocytic mitosis. The nuclei 

 of the other sort are considerably larger (Fig. 13, B, PI. X.), the 

 spireme is much less dense and more irregular in form and does 

 not occupy the whole periphery but is still massed more or less 

 at one side and the nucleolus is still intact. I am confident that 



