364 The Spermatogenesis of Bufo Lentiginosus 
nucleus surrounded, as in the earlier stages, by a clear area (Fig. 64). 
The acroblast finally reaches the anterior end of the cell (Fig. 67), 
and then comes in contact with the nuclear membrane (Fig. 68). Sub- 
sequently the acroblast flattens against the apex of the nucleus (Fig. 69) 
and seems to fuse with it, forming a deeply staining, cap-like body 
(Fig. 70, 71, Ac.). The cytoplasm in the anterior region of the cell 
later forms an awl-shaped apical body in front of the acrosome, which 
stains very faintly with plasma stains (Fig. 71). 
During the later growth stages of the spermatids, the cysts inclosing 
them become disorganized and a cavity appears in the middle of the fol- 
licle. This cavity contains a considerable amount of débris formed from 
the degeneration of the cyst membranes and the follicle cells. Some of this 
débris is in the form of large and small granules which take the chroma- 
tin stain. It is, therefore, somewhat difficult to follow the history of the 
acroblasts, as frequently a spermatid will be found that appears to con- 
tain several rounded, deeply staining granules of about the same size as 
the acroblast. Fortunately, the acroblast in the spermatid is almost 
invariably surrounded by a clear area both before and after it has 
divided (Figs. 58, 61, ete.), and thus it can usually be distinguished 
from granules of débris that often appear to be a part of the cell. In 
studying the history of the acroblast I have made use of sections of the 
testis that were purposely crushed and broken; as by such means the 
spermatids, which are normally crowded close together, are separated 
and partially freed from other material in the follicle. 
The mature spermatozoon of Bufo lentiginosus has already been 
described and illustrated (King, 26). The head is a long cylindrical 
structure which is seemingly homogeneous after the usual staining with 
iron-hematoxylin. If, however, the stain is partially extracted, as was 
done in the preparation from which Fig. 71 was drawn, the head ap- 
pears grayish in color and there are two deeply staining regions, one at 
the anterior, the other at the posterior end. It is evident that the parts 
of the sperm-head that retain the stain with the greatest tenacity mark 
the location of the two bodies that entered the nucleus at an early period 
in the development of the spermatid. At the posterior end of the 
sperm-head lies the inner centrosome which entered the nucleus of the 
spermatid just before the stage of Fig. 66; and at the anterior end is the 
acroblast which fused with the nucleus at about the stage of Fig. 69. 
Both of these structures evidently persist in the mature spermatozo6n 
and retain their great affinity for the iron-hematoxylin stain. 
The middle-piece of the mature spermatozoén (Fig. 71, M@. P.) has 
