72 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
above in detail, seems to me to establish very definitely that the 
- association of paired chromosomes in the pachytene stages is one in 
which the members lie side-by-side throughout their entire length, 
and therefore exhibit parasynapsis. I should further add that while . 
I have not singled out any other members of the complex for individual 
study, a careful analysis of the other spireme segments and the deriva- 
tive tetrads indicates that the condition of parasynapsis is realized 
for the entire series. I was thus able to analyze the stages of the 
complex as a whole after following the history of the selected indi- 
vidual pairs, whereas previously I was unable to reach a definite 
conclusion. 
As to the method of division in the first spermatocytes, the evidence 
presented indicates that B, always, and A, in most cases, divide equa- 
tionally, while C divides either reductionally or equationally and with 
equal frequency by each method. My study of the other tetrads 
leads me to think that, as a general rule, they divide equationally in 
the first division. Where the first division is equational the second 
is regarded as reductional, and we therefore have postreduction. 
The general rule has its exceptions, however, as already noted in the 
case of C and possibly sometimes in the case of A. 
b. The Conjugation of Chromosomes. 
1. The formation of leptotene threads—The evidence for para- 
synapsis derived from a study of the postspireme stages, as presented 
in the preceding paragraphs, has not embraced the actual process of 
conjugation; and it therefore remains to be demonstrated that a 
side-by-side conjugation does take place. But it is even more im- 
portant to show that the conjugants are actually chromosomes, the 
morphological descendants of the telophase chromosomes of the final 
spermatogonial division. Figure 21 (Plate 2) shows a side view and 
figure 22 a transverse (optical) section through the chromosomes of 
cells nearing the end of the telophase of the last spermatogonial divi- 
sion. The side view shows the chromosomes already partly diffused, 
but each one occupies a definite territory, so that there is no question 
as to their persistent individuality, except for the coalescence of some 
of the polar granules. But, as I shall point out later, the polar gran- 
ules do not necessarily lose their identity when they unite into the 
compound masses. ‘The optical section, figure 22, shows even more 
plainly the persistent individuality of the chromosomes up to this 
