280 MR. F. E. BEDDARD ON THE [May 4, 
It seems to me to be fairly certain that the ova represented in Plate 
XXVIII. figs. 1, 2, 4, are progressive stages in egg-development : 
there is a gradual increase of size accompanied by various changes 
in the egg-contents, the germinal vesicle, and the egg-membranes, 
which all tend to prove the truth of this supposition. All these 
different stages were frequently to be observed in a single section. 
In the same sections were a number of very peculiar ova, displayed 
in Plate XXVIII. fig. 3; these were for the most part intermediate 
in size between ova of the third stage (fig. 2) and the more mature 
ova (fig. 4); in a few cases, however, they were distinctly smaller 
than ova of the third stage. This last fact would be hardly sufficient 
of itself to prove that these ova do not form a stage intercalated 
between Stages 3 and 4, because there is often some irregularity in 
size ; larger ova, particularly if they are not much larger, could not 
be positively regarded as more mature than smaller ova. In the first 
place, however, the structure of these ova and the conditions of the 
follicular epithelium are so markedly different from ova of any other 
stage, that it scems difficult to assign them to the same series ; and, 
in the second place, I have been able to observe no transitional stages 
between these ova and those belonging to Stages 2 or 3. On the 
other hand, these ova eventually acquire the same appearance as ova 
that have evidently passed through Stages 2 and 3; to this point I 
shall return later. I must for the present leave it an open question 
as to whether these ova form part of the same series as those dis- 
played in Plate XXVIII. figs. 1, 2, 4, or whether the ovary of Pro- 
topterus contains ova of two kinds which follow a different course 
of development though they ultimately eome to be identical in 
appearance. 
These ova (Plate XXVIII. fig. 3) are surrounded by a follicular 
epithelium which, like that of the other ova, consists of a single layer 
of cells; these cells are long and somewhat columnar in form (Plate 
XXIX. fig. 7) ; they are limited by a distinct membrane and contain 
a darkly stained nucleus as well as a number of highly refracting 
round particles which resemble in every respect the yolk-spherules of 
the contained ovum. These follicular cells rest upon the surface of 
the ovum, and there is no trace whatever of any membrane separating 
them from the ovum. 
The connective-tissue sheath of the follicle was very distinctly 
marked off from the surrounding ovarian stroma; near to the peri- 
phery of the ovum were an immense number of blood-capillaries of 
large size and gorged with blood. These capillaries, although probably 
belonging to the stroma-sheath, were in many cases pressed down 
among the epithelial cells of the follicle, appearing as if they were 
actually lying between the cells; this remarkable appearance of the 
blood-vessels is illustrated in Plate XXIX. fig. 7, which represents 
a portion of the periphery of such an ovum very highly magnified. 
The interior of the ovum contained abundant yolk ; but in no case 
did I succeed in finding any trace of a germinal vesicle. The yolk 
consisted of highly refracting spherules which were for the most part 
of small size, but here and there were very much larger: spherules, 
