SPERMATOGENESIS OF SQUILLA ORATORIA 320 
In the mature state of the spermatozoa the vesicle acquires a 
firm consistency, probably by changing its nature into chitin, 
and it appears refringent. Internally, it contains two com- 
partments, namely, an outer and an inner, called by Fasten 
(18) ‘first or primary vesicle’ and ‘second or secondary vesicle,’ 
respectively. In the Squilla spermatozoon, on the other hand, 
the vesicle is simple, not divided into compartments, and con- 
tains no centrosome; its enclosure takes almost no stain at all 
throughout all stages of the formation of the vesicle. 
A no less important distinction is to be found in the head or 
nucleus. In the Decapoda it appears to have a rather loose 
consistency and often stains but weakly. Thus in the crab 
spermatozoon Binford (’13) has pointed out that it is rather 
difficult to distinguish the nucleus from the cytoplasm in which 
it is imbedded. This is in sharp contrast to the fact that in 
Squilla spermatozoon the nucleus acquires a consistency entirely 
different from that of the cytoplasm and is marked off very 
clearly from the latter. As a matter of fact, this consistency 
of the sperm head reminds one of that of the vesicle of a 
decapod spermatozoon. Moreover, the head encloses the bodies 
derived from the centrosome just as it is in the vesicle of the 
latter spermatozoon. Singularly enough, the head of the Squilla 
spermatozoon shares such important features with the vesicle of 
the decapod spermatozoa. 
There remains to be considered the structures arising from 
the centrosome. Many authors on the spermatogenesis of the 
Decapoda claim that one of the two centrosomes produced by 
division of the original one becomes rod-shape to form the ‘cen- 
tral body’ within the secondary vesicle, while the other main- 
tains that it retains its initial state at the base of its fellow. 
In the present material, too, one centrosome becomes rod-shape, 
while the other undergoes no perceptible change. The question 
naturally arises as to the homology of the two centrosomes of 
Squilla with those of the decapod spermatozoa. As has been 
shown above, in Squilla the centrosome which takes the rod 
shape is the one which is more approximate to the nucleus, 
while the other, remaining unmodified, is the distal centrosome 
JOURNAL OF MORPHOLOGY, VOL. 34, NO. 2 
