2IO 



MAULSBY W. BLACKMAX. 



great number of cells. Of course it is possible that the process 

 varies in different animals, but it is not probable, for if the 

 sequence of the actual divisions varies, we should naturally ex- 

 pect the prophase phenomena to vary in a like manner. No such 

 variation seems to exist. 



The chromosomes as they occur in the metaphase are arranged 

 in no definite equatorial plate but are scattered irregularly through- 

 out the equatorial region of the spindle (Fig. 16). It is also 

 noticeable that the chromosomes do not divide synchronously. 





FIG. 16. X 9^ dia. Early metaphase of first spermatocyte. Showing the diversity 

 in shape of the chromosomes, and their irregular arrangement in the equatorial region. 



FIG. 17. X 9^0 dia. Telophase of first spermatocyte, showing the unequal division 

 of the chromatin, the accessory chromosome being present in one cell while it is absent 

 in the other. 



While some still plainly show their tetrad character, others have 

 completed their separation and have already started toward the 

 poles. 



Owing to the approximately equal size of all the chromosomes 

 and the diversity of shapes which they present it has not been 

 found possible to trace the history of the accessory chromosome 

 during the first metakinesis. However, from an examination of 

 the telophase succeeding, it becomes evident that this element 



