IIO MARGARET REED LEWIS AND WM. REES B. ROBERTSON. 



case however there is usually only one mitochondrial mass 

 (although it may divide into two in some cases) and this mass 

 lies at one side midway between the two poles of the spindle 

 (Fig. 30). The mitochondria migrate away from this granular 

 mass and elongate towards the two poles of the spindle. Usually 

 the elongated threads spread out around the spindle, but in a 

 few cases they have been seen to remain mostly on the side of the 

 spindle where the mitochondrial body was. The threads become 

 homogeneous and appear to be continuous threads stretched 

 between the two groups of chromosomes. When the cytoplasm 

 constricts during anaphase the granules migrate into the daughter 

 cells, but they do not usually scatter around the nucleus. A few 

 neutral red granules are present in the cytoplasm throughout 

 the division and can be seen in the cytoplasm on each side of the 

 mitochondrial body in the spermatid (Figs. 36 and 37). When 

 division is completed the mitochondria granules become con- 

 tracted into a compact, spherical granular body, the nebenkern, 

 and a few neutral red granules are irregularly scattered on each 

 side of the nebenkern. It is interesting to note that after 

 acetic acid vapor, a round body can still be distinguishable in 

 the place of the nebenkern, so that either the mitochondria are 

 at this stage more resistant to acetic acid, or else there is some 

 other body present in the nebenkern. 



In a few cases the daughter cells seemed to be unequal in size. 

 It has not been determined whether the inequality in size of the 

 daughter cells is due to the presence of the sex chromosome in 

 the larger cell. Davis ('08) and Gerard ('09) in their figures for 

 this genus each show one of the daughter cells, which result 

 from the second spermatocyte division, larger than the other, 

 but they do not call attention to this point. 



The Spermatid and Spermatozoon. The development of the 

 spermatid into the spermatozoon is by no means a simple process 

 and, even after prolonged observation, the significance of the 

 various steps is not clear (Figs. 38-51). 



The neutral red granules do not play an active part, but remain 

 about the same in the cytoplasm until with the growth of the 

 tail the cytoplasm becomes small in quantity and they disappear. 

 They were not observed in the more adult spermatozoon except 



