366 The Sperm Centrosome and Aster of Allolobophora Foetida 
posterior granule of the middle-piece functions morphologically as a 
centrosome. The morphological value of this fact is, however, challenged 
by Van der Stricht’s interesting results in his study of the egg of the bat, 
where he finds the rays of the sperm aster focussed around the anterior 
granule of the middle-piece. ‘* Un spermaster se forme tout autour d’un 
corpuscle central, le spermocentre, attenant a l’extrémité antérieure de la 
piéce de réunion de la queue du spermatozoide.” * 
The origin of the sperm centrosome in Allolobophora has been very diffi- 
cult to determine, as preparations showing the exact stage of development 
necessary to decide this point are rarely found. The middle-piece must 
be not only intact, but it must be still attached to the head of the sper- 
matozoon ; for after it is separated from the head its position within the 
sphere (photo. 9) is most erratic. Jis length may be at any angle in 
relation to the head of the spermatozoén, and frequently the whole mid- 
dle-piece is entirely out of the centre of the sphere. This is the stage of 
the male attraction-sphere usually found; and this fact made it impos- 
sible to assign to either of the granules of the middle-piece the morpho- 
logical value which now seems warranted by our recent preparations. 
It is probable that this displacement of the middle-piece in the sphere 
is due to the mechanical effect of the fixatives. ‘The fixatives and the sub- 
sequent technique shrink these eggs, in many cases, one-third of their 
diameter, and this fact indicates that we may expect a displacement of 
the structures, unless we assume that the forces act equally on all the 
constituent parts. In a former paper* we have shown photographs of 
different cytological configurations produced in these eggs by the various 
fixatives, and the displacement of cytological constituents has been demon- 
strated by many investigators. We have nearly a thousand photo- 
graphs systematized in such a way as to facilitate a comparative study 
of the effect of the different fixatives at definite stages of the egg’s devel- 
opment; but the inconstancy of the reactions of the egg to the fixative 
under conditions apparently the same, makes the problem too compli- 
cated to justify hasty conclusions. 
Photos. 1 to 8 show the middle-piece intact and still attached to the 
head of the spermatozoon, while the sphere is formed around the posterior 
end of the middle-piece. In photos. 1, 4, 6, and 8, the posterior granule 
itself is clearly seen. That these granules are larger than those in the 
spermatozoon before it enters the egg—though perhaps due in part to 
2Van der Stricht, O. Le spermatozoide dans l’oeuf de chauve-souris (V. noctula). 
Verhand. d. Anat. Gesell., 1902. 
3 Photographs of the egg of Allolobophora foetida. Journ. Morph., Vol. XVI, 
No. 3, 1900. 
