THE GERM-CELLS OF CICADA (TIBICEN) SEPTEMDECIM. 4! I 



cytoplasm becomes active in the secretion of large globules and 

 although the nuclei increase in number, I have been unable to 

 find mitotic figures and it seems possible that the increase in their 

 numbers is brought about by amitosis. 



2. Spermatocytes . 



(a) Growth Stages. Unfortunately the material wh'ch was 

 collected showed very few of the early growth stages of the 

 spermatocytes and consequently I was unable to make a detailed 

 study of the process of synapsis. Apparently the early growth 

 stages must take place some time before the month of April. 

 In the youngest pupae which I have collected, the only growth 

 stages of the spermatocytes which I have been able to find are 

 those of the pachytene-bouquet stage (Fig. 17) in which the 

 thick synaptic threads are polarized at one side of the nucleus. 

 Sections across the bouquet usually show 18 chromatic blocks 

 representing the end view of the threads. Since each loop has 

 been cut twice, this would indicate that there are 9 pachytene 

 loops. At the base of the polarized bouquet is usually found the 

 compact, deeply-staining nucleolus (Fig. 17, A") which is the 

 persisting sex-chromosome. This is undoubtedly the same com- 

 pact chromatic nucleolus found in the resting stages of the 

 spermatogonia (Fig. 13). As is usual, the bouquet is polarized 

 toward the pole of the cell containing the idiozome (Fig. 17, id.). 

 It has often been stated that the idiozome exerts some attraction 

 on the synaptic threads influencing their polarization. There is 

 no evidence to support this view and I am inclined to believe 

 that the same factors which determine at which point in the cell 

 the idiozome should lie also determines the polarization of the 

 synaptic threads. 



Occasionally the pacyhtene threads show a longitudinal split, 

 and in such cases it is noticed that the chromatic granules 

 (chromomeres) of the two halves of the thread do not correspond 

 either in size or location. Consequently the longitudinal split 

 cannot be interpreted as an equational split, but is rather the 

 primary split or point of synaptic union. Usually there is 

 present a single loop of the bouquet which is much larger than 

 the other loops (Fig. 17, A A) and this undoubtedly represents 



