1 88 MAULSBY W. BLACKMAN. 



aggregated chromatin ; and with the Ehrlich-Biondi mixture, 

 following the action of suitable fixatives, assumes the green color 

 usual to chromatin treated by this reagent. Numerous other 

 stains of a greater or less value as micro-chemical tests were 

 used and with all these the chromatin nature of this body was in- 

 variably demonstrated. 



The character of this nucleolar body which, for reasons late 

 made apparent, I shall call the karyosphere is still further indi- 

 cated by its behavior in the prophase of the spermatogonium. 

 Owing to the advanced development of my material I have beem 

 unable to study any but the last generations of these cells, but I 

 believe that the phenomena here observed are common to all gen- 

 erations of the secondary spermatogonia. In all cases studied, the 

 active prophase is characterized by the presence within the nuclear 

 vesicle of 33 small aggregations of chromatin and the complete 

 absence of the karyosphere (Fig. 2), thus giving a logical basis 

 to the conclusion that the chromosomes are derived directly from 

 the substances of the karyosphere. Of these 33 chromosomes 

 32 are characterized in the earlier prophases by their granular 

 consistency, while the remaining one is plainly distinguishable 

 on account of its homogeneous nature and its clear-cut outline. 

 This modified chromatic element is the accessory chromosome, 

 first recognized as a specialized chromosome by McClung, '99, 

 and later found to be probably of universal distribution in the 

 male cells of arthropods. 



It will be noted that the number of chromosomes, 33, given 

 above as characteristic of the spermatogonium is not a multiple 

 of two as is generally considered to be necessarily the case of 

 immature germ cells. The reason for this fact has to do with 

 the peculiar character of the accessory chromosome, and can 

 readily be explained when the later behavior of this element is 

 known. 



During the following phases in the mitosis of the last generation 

 of secondary spermatogonia, nothing of especial interest with 

 regard to the chromatin occurs until the telophase is reached. 

 This phase endures for a considerable time as is shown by the 

 great number of slightly different stages present and by the fact 

 that more spermatogonia are found in this condition than in any 



