Helen Dean King 375 
Before the outer centrosome has reached the posterior end of the 
middle-piece (Fig. 63), the acroblast divides and one part migrates to 
the anterior end of the spermatid to form the acrosome. The fate of 
the acroblast that remains for a time in the posterior region of the 
spermatid I have not been able to ascertain. It is possible that this 
body has something to do with the formation of the marginal-filament 
or with the tail membrane. I cannot believe that it has persisted through 
all stages in the development of the spermatogonia unless it is to play 
some definite role in the formation of the spermatozoon. 
An examination of the literature dealing with the spermatogenesis of 
amphibians shows that several investigators havé found a homogeneous, 
rounded body in the cytoplasm that is similar in appearance to the 
acroblast in Bufo. Although Flemming and Meves makes no mention 
of such a body in the sperm-cells of Salamandra, Hermann states that 
in the spermatids of this amphibian “ ein ovalirer K6rper von dichterer 
Consistenz findet sich; von einem hellen Hof umgeben.” According to 
Hermann this body is formed in the spermatid from the remains of the 
achromatic spindle apparatus of the last spermatocyte division and soon 
disappears, being of secondary significance in the formation of the 
spermatozoon. Figures given by Kingsbury of the spermatogonia of 
Desmognathus show bodies in the cytoplasm resembling the acroblast, 
but no mention is made of these bodies in the text of the paper. The 
oval bodies found by Janssens in the spermatogonia of Triton are very 
like the acroblast in Bufo; but Janssens believes that these bodies are 
nucleoli extruded from the nucleus in order to nourish the cytoplasm. 
The behavior of the acroblast in Bufo would seem to invalidate the as- 
sumption that this body is an extruded nucleolus. As a rule, nucleoli that 
are ejected from the nucleus are dissolved at once or they lose their 
power of staining intensely and break up into granules which soon dis- 
appear. The acroblast, on the contrary, maintains its homogeneous ap- 
pearance and stains very intensely during all stages of its development ; 
it grows somewhat during the rest period of the cell, and then divides in 
the early prophase of mitosis, thus persisting as a definite structure in 
all generations of the sperm-cells. 
In the cytoplasm of the spermatocytes and spermatids of various other 
groups of animals, small rounded bodies have been found that possibly 
are of the same character as the acroblast in Bufo. Since Benda (1) 
described the “ chromatoid Nebenk6rper ” in the spermatocytes of mam- 
mals, a similar body has been found by other investigators of mammalian 
spermatogenesis. Lenhossek identifies the homogeneous body that is 
4 
