368 The Sperm Centrosome and Aster of Allolobophora Foetida 
We might assume this if one of the granules could be traced to the cleav- 
age stage, but at the telophase of the second maturation-division, both 
egg and sperm-attraction spheres, with their centrosomes, disappear. Until 
improved technique enables us to trace the centrosome through these 
stages, the evidence given by Allolobophora still points to the de novo 
origin of the cleavage centrosomes. 
EXPLANATION OF PLATE I. 
The photographs of this plate were taken by the method described in 
full in Zeit. f. wiss. Mik., Bd. XVIII, 1901. “‘ A new method of focussing in 
photomicrography.”’—Foot and Strobell. 
In order to economize space only a small part of each section is shown in 
the photographs. 
All the sections were stained with iron hematoxylin, in most cases with 
an after stain of dilute Bismark brown. 
Puoro. 1. Section (3,,) of odcyte, second order, showing the male attrac- 
tion-sphere with the posterior granule of the middle-piece forming the 
center of the sphere. The middle-piece of the spermatozo6n is intact and 
still attached to the head, part of which appears in this section, the rest 
of the head showing in four neighboring sections. Fixative Perenyi’s 
fluid. X 1000. 
PHOTO. 2. Section (2%) of odcyte, second order, showing the male 
attraction-sphere with the posterior end of the middle-piece nearly in the 
center of the sphere. The middle-piece of the spermatozoon is intact and 
still attached to the head, part of which shows in this section. The rest 
of the head in three neighboring sections. Fixative Hermann’s fluid. 
x 1000. 
PuHoTO. 3. Section (3 ) of odcyte, second order, showing male attraction- 
sphere with posterior end of middle-piece in the center of the sphere. 
The middle-piece is intact and still attached to both the tail and head of 
the spermatozo6n. The rest of the head is in the next section. Fixative 
corrosive sublimate. X 1040. 
PuHoro. 4. Section (3,,) of odcyte, second order, showing male attraction- 
sphere with the posterior granule of the middle-piece demonstrated in the 
center of the sphere. The middle-piece of the spermatozoon is intact, and 
is still attached to the head, a part of which appears in this section. The 
rest of the head is in the next section. Fixative Perenyi’s fluid. X 1000. 
Puoro. 5. Section (3,,) of odcyte, second order, showing male attraction- 
sphere with posterior end of middle-piece in the center of the sphere. 
The middle-piece of the spermatozo6dn is intact and still attached to the 
head, a part of which appears in this section. The rest of the head in the 
two following sections. Fixative corrosive sublimate. X 1000. 
PuHoTo. 6. Section (3,,) of odcyte, second order, showing male attraction- 
sphere with the posterior granule of the middle-piece demonstrated in the 
center of the sphere. The middle-piece of the spermatozo6n is intact and 
still attached to the head, a part of which appears in this section; the rest 
of the head in three neighboring sections. Fixative corrosive sublimate. 
x 1000. 
