430 EDWARD E. WILDMAN 
is evident that no division occurs among the vesicles. Their 
number, which is remarkably uniform in all the cells of a tube, 
seems to be determined, therefore, by the amount of transuding 
karyochondria. 
Destiny 
Just before the first maturation division the centrosomes 
emerge from the nucleus. The refringent vesicles at once begin 
to arrange themselves in concentric arcs about them. This sym- 
metrical arrangement is kept throughout the divisions. The close 
of the anaphase of the second division is marked by two interest- 
ing events; the fusion of the centrosome with the two chromosomes 
in each spermatid, and the withdrawal of small, dense granules 
(plastochondria) from the refringent vesicles (fig. 34). 
When the new spermatids separate they are spherical, and in 
them the vesicles are arranged radially and concentrically in 
four or five layers. Each spermatid has at its center the fused 
centrosome and chromosomes, surrounded by a clear mass of 
cytoplasm, or the ‘perinuclear zone’ of Van Beneden. In this 
zone lie the plastochondria, or ‘microsomes’ of Van Beneden. In 
the great majority of males killed one finds only spermatids of 
this form filling the vas deferens (figs. 12 and 35). Among them, 
however, are many which show ‘cytoplasmic reduction,’ a phe- 
nomenon now recognized in the development of the spermatids of | 
a good many animals. In these, probably the older ones, a mass 
of eytoplasm containing plastochondria but without refringent 
vesicles, gradually flows out from the spherical spermatid and 
is cut off from it (figs. 13 and 14). Romieu (11) was the first 
to describe this phenomenon in Ascaris. Asa result of this loss, 
the volume of the spermatid is often reduced one-half, and the 
vesicles are thus brought close together. 
In extremely rare cases a male will be found in which the sper- 
matids are transforming into spermatozoa. This transformation 
probably occupies only a few minutes, and takes place just be- 
fore copulation occurs. 
In these the vesicles gradually fuse together until they form 
three or four large globules which surround the clear zone (figs. 
25 and 36). Indeed, this is usually encroached upon, and some- 
