4 C. ISHIKAWA. 



drawn from the testis of another inclividual, a cell found in tliis region 

 Avhich represents a further stage of division, in which the chromatic 

 elements are already separated from each other and lie near the poles 

 of the spindle. I will call these primitive cells by the name oî primary 

 spermatic cells ("Ursamenzellen" of German authors). They generally 

 divide two or three times, and thus fAve rise to the cells of the o'r(3wino' 

 zone which will be ; poken of as sperm-mollicr -cells ("Samenmutterzellen" 

 of German authors). 



h. Tlie Groioinii Zone. — The cells at the beoinnin<>' (^f this zone 

 are relati\'e]y small and the eight chromosomes begin gradually to 

 elongate and at the same time the nuclear membrane becomes distinct. 

 Hand in hand with this change the cell-body enlarges, while the 

 nucleus appears to get snndler and more conipr.ct, colouring very 

 deeply with reagents, and at last Ijecomes quite homogeneous, owing 

 to the thick consolidation of the chromosomes. These stages are seen 

 in tigs, o, 4, and 5. In fig. 3 the chromatic elements are just begin- 

 ning to elongate, have continued to change in cells represented by 

 fig. 4, and lastly in fig. 5 ha^e become quite homogeneous. 



The next chano-e in the cells is the dissolution aji-ain of the 

 elements (figs. 6 and 7, the former rejH'esenting the polar view and 

 the latter that from the side). Instead of a homogeneous mass we now 

 see a number of elon^'atcd chromosomes irrei>'ularlv Ivino- in the 

 centre of a cell, Ijut generally more or less gathered to one side 

 remindinsf one reinarkabJv oï the fi^-ures i^iven by Hertwin in the 

 same stages of development in the spermatic cells of Ascaris mcijalo- 

 ccphala. Tlie only différence between them and our figures consists 

 in the absence of a nuclear membrane in the latter. The chromosomes 

 become shorter and thicker and assume at last a short rod-like shape 

 just as we find them in primary speruuitic cells preparing to divide. 

 Fig. 8 represents these changes. At the left hand of the figiu'e is 



