SPERMATOGENESIS OF SQUILLA ORATORIA aal 
Figure 51 represents a mature spermatozoon. It is a spherical 
vesicular body and bears a lens-shaped nucleus, the head, at one 
pole of the sphere. The size of the spermatozoon is from 9 to 
11p in diameter, while the head measures from 4 to 4.5u in trans- 
verse and 2.5u in vertical diameters. The membrane of the 
vesicle is fairly thick and appears to be somewhat resistant 
against pressure. Its outer surface seems to be covered with 
some glutinous matter, since the mature spermatozoa forms a 
compact mass in the cavity of the vas deferens. The vesicle con- 
tains a hyaline substance which coagulates when fixed, and then 
presents a faintly granular appearance. The head consists of, 
1) a main part, homogeneous in consistency; 2) a subordinate 
conical part of granular appearance, representing the perfora- 
torium; 3) a rod-shaped body. standing in the axis of the per- 
foratorium and derived from the proximal centrosome, and, 4) 
the distal centrosome imbedded within a vacuole occurring in 
either parts 1 or 2, or on the boundary of these two. The head 
is highly yefringent and appears very compact. It is, moreover, 
very resistant and hard to disintegrate, although often its shape 
changes to some extent by fixation. Both Gilson (’86) and 
Nichols (’09) recognized that the mature spérmatozoon of 
Squilla is a spherical vesicular body, at one pole of which is 
attached the lens-shaped or button-like head. No accounts 
however, are to be found about the more minute structure of the 
head, especially that of the centrosome and the body derived 
from it. 
GENERAL DISCUSSION 
a. Synapsis 
Recently, ample evidence has been accumulated in favor of 
the occurrence of parasynapsis, instead of telosynapsis, through 
cytological studies upon various forms of animals. Especially 
works by such authors as Grégoire (710), Montgomery (’11), 
Wilson (12), and Wenrich (’16) seem to have demonstrated in 
the clearest way the validity of that view. As also in higher 
crustaceans, Fasten (14, ’18) maintains parasynapsis, and his 
