SPERMATOGENESIS IN ASILUS SERICEUS 171 
These are double and haploid in number, corresponding to the 
telophase pairs. The size of the cells and nuclei indicate that 
the actual growth period has barely begun when these bodies 
become visible (fig. 11), and there seems to be little doubt that 
the preceding transition from the telophase stage has not only 
been very brief, but has involved little change in the chromo- 
somes other than that involved in the loss of staining capacity. 
The intimate association in pairs appears to have remained 
unaltered. 
The chromatin now becomes further condensed, revealing the 
size and shape of the bivalents in a more clear-cut manner (figs. 
12 and 13). Attached to one of these (apparently the smallest 
pair) is the nucleolus, the history of which will be considered 
later. This stage may be designated stage b. Structurally 
stage b resembles the late resting stage or early prophase of the 
spermatogonia in which the chromatin becomes condensed into 
five bivalent aggregates that give rise to the prophase chromo- 
somes.^ 
Since stage b forms a definite point of orientation between 
the brief early stages and the more extended later ones, it may 
be well to consider events up to this time before describing the 
subsequent processes. It is apparent that the synaptic condition 
has been fulfilled at the very beginning of the growth period by 
the intimate association in telophase of chromosomes that were, 
for the most part,^ already arranged in pairs. Technically, this 
association should be called synapsis, for, as will be seen, the 
union effected in telophase persists throughout the growth period 
and is responsible for the formation of the bivalent chromosomes 
of the first maturation division. 
Compared with the corresponding stages in other animals, 
this behavior seems to be unique, and it seems legitimate to 
infer that it is associated in some causal manner with the other 
^ See footnote 3, page 169. 
^ It is not justifiable to assume that the paired association in anaphase is 
absolute and invariable, for occasionally the two members of a pair may be sep- 
arated in metaphase (e.g., fig. 4), and consequently in anaphase. It must be 
assumed, however, that in these exceptional cases the i)aircd arrangement is 
restored in telophase or soon thereafter. 
THE JOURNAL OP EXPERIMENT.4.L ZOOLOGY, VOL. 32, NO. 1 
