376 The Spermatogenesis of Bufo Lentiginosus 
present in the spermatocytes of the rat with the “ chromatoid Neben- 
korper ” of Benda and he concludes, from its staining reactions, that 
it is an extruded nucleolus whose function may be to give up substances 
to the cytoplasm of the spermatid that are of use in the formation of the 
tail. Niessing also mentions the presence of a similar body in the 
spermatids of the guinea-pig, of the rat, and of the mouse. He traces 
this body back to the spermatocytes, although he fails to follow its his- 
tory in the spermatids. Figures given by Niessing (Nos. 6, 21, 31, and 
34) show that this body is in all respects like the acroblast in Bufo. His 
Fig. 34, showing a section of a young spermatid of a mouse, is especially 
interesting because in it this body is distinctly dumbbell shape, thus 
plainly indicating that it is in the process of division (compare with my 
Fig. 22,4). This stage given by Niessing is the one that I have been en- 
deavoring in vain to find in the spermatids of Bufo; for although I have 
found numerous instances in which two acroblasts were lying close to- 
gether, I have never succeeded in finding the actual division stage. It 
is a rather significant fact that Niessing is one of the few investigators 
who have stated that the acrosome is derived from a spermatid centrosome. 
The acroblast in the young spermatids of Bufo might readily be mis- 
taken for a large centrosome if one had not traced its development up 
to this stage. I am inclined to think, therefore, that the presence in 
the spermatids of other forms of a body similar in nature to the acroblast 
in Bufo may have caused many of the conflicting results that have been 
obtained by investigators regarding the origin of the acresome. On this 
assumption it is probable that the “ centrosome” described by Niessing, 
Field, Platner, and others as forming the acrosome, will be identified 
with the acroblast that migrates to the anterior end of the spermatid of 
Bufo; the real centrosome being found in the posterior end of the 
sperm-head or in the middle-piece. Platner’s figures of the sperma- 
tids of a butterfly (Figs. 6-9) readily lend themselves to this interpreta- 
tion, as his “centrosome” is much larger than that usually found in 
the spermatids of insects. 
Besides the work of Platner, Henking’s (19) figures of the sperm- 
atids of Pyrrhocoris apterus strongly suggest that a body like the acro- 
blast may be present in the sperm-cells of some of the invertebrates as 
well as in those of the vertebrates. In addition to a nebenkern and a 
mitosome, both of which he derives from the remains of the spindle of 
the last spermatocyte division, Henking figures in the cytoplasm a small 
rounded, deeply staining body (Figs. 68, 69, 71, 72, 77-80). In the 
young spermatid this body seems to have no definite location, but in later 
