86 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
attached to the nucleus, where the vesicle and its contents continue to enlarge 
(Fig. 42). The clear fluid originally filling the vesicle is now gradually dis- 
placed by the expanding intermediate substance which grows out from the 
central staining body until it fills nearly the whole of the vesicular space (Fig. 
43). The clear substance is, as it were, forced down upon the nuclear mem- 
brane, and forms a clear collar in the manner represented in (Figs. 45, 46, 47, 
48). The intermediate substance continues to grow, and finally begins to 
encroach into the cup-shaped space occupied by the clear substance until 
ultimately the latter assumes the form of a ring round the nucleus, as in 
(Figs. 48, 49, 50). 
At this time the nuclear membrane gradually disappears over that part 
of the nucleus which is underneath the ring formed by the clear vesicular 
substance, and for a time the substance of the vesicle and that of the nucleus 
seem to be in for communication (Figs. 49, 50, 51). The central staining body 
of the vesicle also grows, becomes half-moon shaped, and closely attached to 
the nuclear wall. In like manner the intermediate substance continues to 
grow, and follows the clear substance over the surface of the nucleus to the 
point at which the bulging annulus existed, the latter now gradually shrinking 
(Pigs. 51, 52, 53). From the zone round the nucleus now reached by the 
vesicle fine out-growth proceed in the manner described by Meves, and these 
ultimately form a hollow tube projecting beyond the opposite pole of the 
nucleus, and containing the centrosomes, and the base of the spermatic tail. 
While the above changes have been going on the centrosomes have come 
to he near the nucleus, opposite the vesicle, and from one of them a tail 
grows out as represented in (Figs. 48 — 52), both centrosomes, together with 
the base of the tail becoming eventually enclosed in a tube proceeding from 
the nucleus as above described. 
For the further details of the completion of the spermatozoon the reader 
may be referred to the above cited work of Meves. It is sufficient for our 
present purpose to point out that the archoplasmic vesicle (Phmmer's body), 
after arising in the above manner, constitutes the anterior cap of the sperma- 
tozoon, and the archosome, as well as the tubular sheath for the tail. 
REMARKS. 
For the foregoing description it will be seen that: — 
The maiotic phenomena in mammals, so far as the nuclear structures are 
concerned, conform with the general scheme of this process given in the joint 
memoir by Professor Farmer and one of ourselves. We here reach, as 
was briefly pointed out in that publication, a similar result regarding the 
nature of the maiotic divisions as that obtained independently by Korschelt in 
the case of 0 phryotrocha, and in the same year as ourselves by Montgomery, 
in amphibia. Still later similar results have been attained by Strasburger and 
others in relation to plants. 
In the first maiotic (heterotype) division the synaptic aggregates are 
formed by the association of pre-maiotic chromosomes, and those in the 
ensuing mitosis simply separate from one another, the existing longitudinal 
split in each chromosome taking no part in the division, and persisting irn 
the diastral stage of the mitotic figure. 
