348 The Spermatogenesis of Bufo Lentiginosus 
found two kinds of nucleoli in the primary spermatogonia of Triton; 
but I have not been able to confirm his statement that the plasmosomes 
pass out of the nucleus and serve as nourishment for the cytoplasm. In 
Bufo the plasmosomes are always found in the nucleus until the early 
prophase of mitosis, when’ they completely disappear, as do also the 
chromatin-nucleoli; the latter are doubtless used in the formation of 
the chromosomes. 
In the resting stages of the primary spermatogonium, the centrosome 
is a minute, deeply staining, spherical body, lying in the cytoplasm near 
the nucleus and usually in one of the numerous indentations of the 
nuclear membrane (Fig. 1, C). The centrosome at this time is always 
inclosed in a rounded, granular attraction-sphere that is very similar to 
the one found by Rawitz (48) in the resting spermatogonia of 
Salamandra. 
In addition to the centrosome and its attraction-sphere, there is present 
in the cytoplasm of the primary spermatogonium a round, or slightly 
oval, apparently homogeneous body that is considerably larger than the 
centrosome near which it is generally found (Fig. 1, A). Usually, 
though not invariably, this body is surrounded by a clear area which 
sharply marks it off from the cytoplasm. It is probable that this structure 
is to be identified with the “chromatoid Nebenkorper ” found by Benda 
(1) in his study of mammalian spermatogenesis. Benda states that the 
chromatoid Nebenkorper has nothing to do with the centrosome or with 
the attraction-sphere, and that it is probably chromatin that has been 
ejected from the nucleus. He finds that this body disappears in the sper- 
matid and he traces it back to the spermatocyte, but ventures no conjec- 
ture as to its probable function. In size and shape this body in the sper- 
matogonia of Bufo greatly resembles the smaller chromatin-nucleoli; but 
in corrosive-acetic preparations stained with Delafield’s haematoxylin and 
orange G, it invariably takes the plasma stain and appears as a con- 
densed portion of the cytoplasm. I have not been able to determine the 
origin of this body which is present in the primary spermatogonia of the 
young toad long before metamorphosis; but, judging from its staining 
reactions, it is certainly not chromatin. As will be shown later, this 
body is undoubtedly concerned in the formation of the acrosome of the 
spermatozoon, and therefore I suggest for it the name acroblast as some- 
what more appropriate than “ chromatoid Nebenkorper.” 
When the spermatogonium is in the early prophase of mitosis, and 
before the nuclear membrane has broken down, the acroblast becomes con- 
stricted through the middle as shown in Fig. 22, A, and then divides. The 
