608 NATHAN FASTEN 



2. First maturation stage 



a. The growth period, including synapsis and tetrad formation. 

 The following stages may be readily distinguished during this 

 period : 



Stage A (figs. 7-8): Early prophases. The autosomes of the 

 ultimate spermatogonial telophases grow irregular, massed, and 

 then weave out into thin threads. 



Stage B (fig. 9) : Leptotene stage. Here the autosomes have 

 entirely transformed into very thin threads. 



Stages A and B (figs. 7-9) represent t|;ie presynaptic stages, 

 and are the most important steps in tracing out the exact process 

 of synapsis. Montgomery ('11) regards them as the 'decisive' 

 stages in truly comprehending the method of chromosomal con- 

 jugation. 



In the forms studied, there are so many chromosomes at these 

 periods that it requires the most painstaking study to determine 

 what occurs. As akeady stated, in stage A (fig. 8) the auto- 

 somes of the last spermatogonial telophases (figs. 6 and 7) are 

 transformed into leptotene threads. This is not accomplished 

 by an uncoiling process such as Wilson ('12), has described in 

 Oncopeltus and Lygaeus, but the chromosomal masses seem to 

 diffuse out into threads in a manner similar to that which Mont- 

 gomery ('11) has described in Euschistus, and the Schreiners 

 ('06 a and b) have described in Tomopteris, Spinax and Myxine. 



In stage B (fig. 9) these leptotene threads have completely 

 formed and all the chromatin masses have disappeared. But 

 no distinct spireme is formed, for the threads can be clearly 

 identified as separate bodies both in smear preparations and in 

 sections. These threads are so numerous that they cannot be 

 counted. It is therefore impossible to state whether each of 

 them corresponds to one of the chromosomes of the telophase 

 stage in the spermatogonial division. The chromosomes in the 

 latter period are also very numerous and their number could not 

 be determined. From a comparison of figures 6 to 9, however, 

 it is evident that the leptotene threads are formed by an unravel- 

 ling of the chromosomes of the spermatogonial telophases and 



