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 otiier 

 stage, that it stems 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 come 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. 



