226 KIYOSHI MASGI. 



constrictions, tlie accessory being divided into two at the same time (Figs. Ill, 

 112). If this view be right, and wo liixve reaSDU to think it so, the second 

 division is simply an ordinary mitosis. 



At the anaphase when the chromosomes arrive at the poles they are as 

 usual gathered iogether into a mass, and it is difSeult to distinguish their indi- 

 vidiudities (Figs. 114, 115). 



The mitochondria : — In the metaphase of the first reduction division the 

 mitchondrial gi-anules lie outside the spindle, being scattered all over the cell 

 body. At the anaphase they remain undivided, but aft^r the division the 

 granules seem to be approximately equally distributed in the daughter cells. 

 In the resting secondary spermatocj-te they are also seen scattered all over 

 the cell. In the second reduction division they repeat the san:e behavior a-s 

 in the first division. 



Even though the amount of ths mitochondrial granules vary considerably 

 according tj the stage, it is clear that they are of very small number 

 compared with those of the mouse. As in the mouse the size of the granules 

 is variable, not ouly in the cells of different stages but also in those of the 

 same stage. 



The chromatoid body: — In the fii-st reduction division the chromatoid 

 body like that which we found in the mouse rarely appears (Fig. 110), this 

 is also the case in the secondary spermatocyte (Fig. 111). 



The resting stage of the secondary spermatocyte : — ^The nuclei of the resting 

 secondary spermatocytes contain several chromatin masses ; and no special 

 chromatin nucleolus can be found among them. 



IV. The Spermatids up to the Formation of the Speumatozoa. 



A. Si^ermatid in the mouse. 



Immediately after the second division, the chromosomes begin to break 

 up and the nucleus enters the resting stage (Fig. 143). The resting nucleus 

 of the spermatid usually contains several chromatin masses and a few -chromatin 

 gi-anules which are scattered along the liuin threads (Fig. 143). The 

 chromatins are gradually gathered together in the center of the nucleus 

 where the nucleolus is situated (Figs. G7, GS, 144). Tlie nucleolus can 



