28 bulletin: museum of comparative zoology. 



divisions. Toyama thinks that the Vierergruppen break up into their 

 four elements, and that these arrange themselves around the equator 

 of the spindle in a single row. He has figured spermatocytes with seven 

 Vierergruppen (Figs. 44, 45), and he tells us that there are 28 sep- 

 arate chromosomes on the spindle of the first maturation division. We 

 must seek his proof of this statement in his Figures 50-52. These seem 

 to me to present seven quadrivalent rings, rather than 28 single chromo- 

 somes. In his Figure 50 Toyama has represented only 7 chromatic bodies 

 on the spindle. Are we to suppose that there were 21 on the other side 

 of the spindle? Our author has given no equatorial view of the spindle 

 in which simple spherical chromosomes are arranged in one row. His 

 Figures 50 and 51 represent what he has considered stages in the trans- 

 verse division of the simple chromosomes. But I have seen in Calop- 

 tenus chromatic rings in such a position as to give exactly the same 

 appearance. In Caloptenus there is no transverse division of the chro- 

 mosomes in the maturation divisions. The ring does not break up into 

 four simple chromosomes before the period of metakinesis. The separa- 

 tion of the ring into its four constituent elements takes place upon the 

 equator of two successive maturation spindles. On the first spindle 

 each ring is separated into two dumb-bell figures. On the second 

 spindle each dumb-bell divides into its two simple chromosomes. Both 

 of these divisions are effected by a breaking of the linin fibres between 

 the chromosomes, not by division of the chromosomes themselves. 



Toyama's description of the origin of the " Nebenkern " from the 

 remains of the interzonal filaments of the last spermatocyte division is 

 essentially the same as I have given for Caloptenus, but he has followed 

 its fate in the spermatozoon farther than I was able to do. His "mito- 

 soma " may be identical with the body which I find in the neck of the 

 spermatozoon of Caloptenus. 



January 19, 1895. 



