456 WILLIAM M. GOLDSMITH 
area gradually enlarges with the increase in length of the cyto- 
plasmic tail, until a very conspicuous sphere is formed (figs. 60 
to 63). Although this body could not be followed in other stages, 
it is assumed, by comparison with other forms, to be mitochon- 
drial. The increase in the radius of this mitochondrial sphere 
places it in closer proximity to the nuclear wall. <A faint filament 
—the first rudiment of the future axial filament—is now present 
(figs. 62 and 63). At the point of attachment of the filament to 
the nuclear wall, one or more small irregular bodies which are 
later concealed in the middle piece can usually be observed. 
Figure 63 represents the culmination of this entire process, both 
in the formation of the chromosome-like bodies of the spermatid 
nucleus and also in the development of the extranuclear sphere. 
The chromatin masses again become less compact and are dis- 
tributed quite evenly throughout the nucleus. The nucleus now 
becomes more pointed at the end opposite the place of attach- 
ment of the axial filament (figs. 63 to 66). The cytoplasmic- 
like sphere and the cytoplasm elongate and condense to form the 
tail. 
The junction between the extranuclear body and the basal 
part of the nucleus now becomes very dense (fig. 66). The 
following processes are so exceptional that it seems impossible 
for this plate to remain as the middle piece of the mature sperma- 
tozoon. Especially well differentiated material revealed the 
fact that this body was not a uniform plate as it usually 
appeared, but that it was made up of chromatin-staining bodies 
of various sizes. These chromatin-staining bodies, to which the 
axial filament seems to be attached, later appear more compact, 
move to one side, and then toward the anterior end of the nu- 
cleus (fig. 67). This change in position causes the filament to 
shift to one side and finally to come in contact with the wall of 
the elongated mitochondrial body (figs. 66 to 69). As the 
chromatin-staining mass proceeds forward (figs. 67 to 70), it 
gives indications of a bivalent nature and soon presents two 
conspicuous bodies which take their place near the forward end 
of the spermatozoon (figs. 71 and 72). Asa result of this migra- 
tion, the middle piece seems to become drawn out into a long 
