Katharine Foot and E. C. Strobell 367 
fixation—is in keeping with the fact that the spermatozodn increases in 
size as soon as it enters the egg, the head becoming longer and broader, 
before it begins to contract into the short thick rod of later stages. This 
separation of the head and middle-piece appears to be caused by the con- 
traction of the head rather than by the migration of the middle-piece and 
sphere. The separation of the contracted rod from the middle-piece 
(photo. 9) is no greater than the contraction of the head would neces- 
sitate. 
In photograph 9, although the middle-piece is separated from the 
head, its posterior end—the one farthest from the head—is almost exactly 
in the centre of the sphere. 
Photograph 10 shows the male attraction-sphere and a cross-section 
through the posterior end of the middle-piece, with the tail of the sper- 
matozoon still attached to the posterior granule. The artificial appear- 
ance of the tail in this section (probably due to the fixative) would make 
us hesitate to interpret this structure as the tail of the spermatozoon, if 
we had not often found the tail persisting until this stage, in eggs killed 
in other fixatives. Photographs of some of these preparations were 
shown in an earlier paper." Photo. 3 also shows an indication of the per- 
sistence of the tail; the middle-piece being still attached to both head 
and tail, its posterior granule forming the center of the sphere. 
In photo. 7, part of the head of the spermatozodn and its middle-piece 
are clearly defined, and the rays of the aster focus at the posterior end 
of the middle-piece. ‘he posterior granule of the middle-piece is oblit- 
erated by over-staining. 
The demonstration of the morphological value of this granule encour- 
ages us to hope that we shall find preparations showing that the acro- 
some forms the focal point for the first rays of the fertilization-cone, thus 
warranting our assumption of a morphological value to this centrosome- 
like granule, and supporting our interpretation of the morphological 
similarity of the male attraction-sphere and the fertilization-cone. 
Although we are forced to the conclusion that these preparations indi- 
cate that a definite part of the spermatozoon itself forms the centrosome 
of the male attraction-sphere, Allolobophora fails to offer any evidence 
that this centrosome gives rise to one or both of the cleavage centrosomes. 
At a later stage the entire middle-piece disintegrates into several gran- 
ules ° and disappears completely, and there is no proof that the granule 
which persists the longest is the posterior granule of the middle-picce. 
*Photographs of the egg of Allolobophora foetida. Journ. Morph., Vol. XVJ, 
No. 3, 1900. 
>Photographs of the egg of Allolobophora foetida. Journ. Morph., Vol. XVI, 
No. 3, 1900. : 
