SPERMATOGENESIS OF SQUILLA ORATORIA 309 
matozoon multiply exclusively by direct division. In the 
nucleus of those cells the spireme is formed, which is segmented 
into chromosomes. The sperm-cell undergoes almost no changes 
in external form until it becomes a mature spermatozoon. This 
latter process is initiated by the appearance of a small vacuole 
in the nucleus; this vacuole then enlarges considerably until it 
fills the greater part of the nuclear cavity, so that the nuclear 
substance comes to be pressed toward one pole of the nucleus 
against the nuclear membrane and assumes a cupule shape. 
The substance next concentrates, becomes homogeneous, and 
further continues to diminish in thickness for a while. Soon, 
however, the central part of the cupule-shaped body becomes 
inflated to take a button-shape and is brought into the cavity of 
the vacuole. In the meantime, the nucleus has a considerable 
growth, while the size of the cell remains nearly constant, so that 
it naturally follows that the cytoplasm is reduced a great deal. 
When, finally, the nucleus reaches full development, it fills 
the entire cell, the cytoplasm being completely lost, and the 
nuclear membrane fuses with the cell-membrane. The mature 
spermatozoon forms a vesicular corpuscle, spherical in shape and 
furnished with a very thick membrane. It contains a hyaline 
liquid, in which some plasmic remains may be recognized. At 
one pole of the wall of the vesicle the button-shaped body is 
attached; this generally is homogeneous, but may occasionally 
enclose a small vacuole. In the vas deferens the spermatozoa 
are agglutinated together by a cementing material into a firm 
cord. 
More recently, (09) Nichols described and figured the sper- 
matozoon of Squilla, together with that of several other crus- 
taceans. She says that the spermatozoon is ‘‘spherical in shape, 
the greater part of the cell consisting of a colorless vesicle filled 
with hyaline substance, while the only portion staining with 
“methyl green is a button—or lens-shaped body at one pole of 
the sphere.’”” She assumed the spermatozoon ‘to forecast’ that 
of the Decapoda. 
