\'2 II. L. WIEMAN 



servation of iMiapluisi^s wluit liappciis in this division. Every- 

 thing would ))oiiil. liowovei', to a division of all the chromosomes; 

 A' and )' being sej)arated and passing to opposite poles. 



1 niu utterly unable to confirm von Winiwarter's statements 

 and figures as to the number of chromosomes. I have occa- 

 sionally- found giant spermatogonia in which about 48 chromo- 

 somes could be counted, but these from their rarity obviously 

 cannot represent the normal condition. Figure 3 shows a met- 

 aphase plate of one of these giant cells. Further, the difference 

 in results cannot be due to difference between European and 

 American, because it happens that the subject whichfurnished 

 the white human testis on which most of my observations are 

 based was a native of Germany. It would appear from the most 

 recent evidence of other investigators that conditions described 

 by von Winiwarter constitute an exception the explanation of 

 which is not yet clear. 



III. .SUMMARY 



1. The metaphase plates of human spermatogonia contain 

 24 straight or bent rod-shaped chiomosomes, two of which are 

 presumably idiochromosomes forming an XY pair. 



2. Throughout the growth period of the primary spermatocyte, 

 the idiochromosomes persist as a basic staining bipartite bodj'' 

 whose components are sometimes separated in which case there 

 are two chromatin nucleoli in the nucleus instead of a single 

 paired one. 



3. In the prophase of the piimaiy spermatocyte 12 bivalent 

 chromosomes appear, one of which is the XY pair. 



4. The XY pair divides longitudinally in the primary sper- 

 matocyte division. The remaining 11 bivalent chromosomes 

 also divide in this division but whether quantitatively or quali- 

 tatively was not determined. 



5. An interkinesis stage follows in which the nucleus contains 

 a double chiomatin body resembling the chromatin nucleolus 

 of the first spermatocyte. It is suggested that this body is one 

 half of the longitudinally split XY pair of idiochromosomes which 

 persist throughout the interkinesis stage. 



