1886.] MR. ROSSliT ON THE FAUNA ETC. OF THE MALDIVES. 29.5 



two layers, the external of which has pores, which are larger and 

 less numerous than those of the inner layer. The egg adheres by 

 the surface of the external layer, but no separation of the two layers 

 takes place. In Osmerus eperlanus the same differentiation occurs, 

 and the external layer, after becoming attached by one point or 

 other, detaches itself from the inner layer except at one circular 

 area, thus forming a membrane by which the ovum is suspended 

 from its attachment. 



It remains to be mentioned that in the unripe ova, which are 

 forcibly expressed from the parent, there is a delicate structureless 

 membrane external to the zona radiata. This is doubtless derived 

 from the ovary ; it is perhaps the connective-tissue layer of the 

 follicle, which becomes reduced in thickness as the egg attains its 

 mature size ; it is certain that the perfectly ripe ovum is envelojied 

 only in its double zona radiata. 



EXPLANATION OP PLATE XXX. 



Fig. 1. Nearly ripe ovum of Osmerus eperlanus, taken from female, and 

 examined in fi-esh condition, a. Thin membrane derived from the 

 ovary, not present in the naturally deposited mature ovum. z.r. 

 Zona radiata; its division into two layers is not shown, g.v. Germi- 

 nal vesicle. (Zeiss A, Oc. 2.) 



2. Outline of attached ovum of Osmerus, s.m. The suspensory membrane 

 formed by the zona radiata externa, z.r.i. The zona radiata interna. 

 (Zeiss A, Oc. 2.) 



r.. The membranes of an almost mature ovum of Osmerus, as seen in the 

 fresh state after rupture of the zona radiata externa by pressure of 

 the cover-glass, s.r.t. Zona radiata interna, s.r.e. Zona radiata 

 externa. (Zeiss A, Oc. 2.) 



4. The zona radiata of egg of Osmerus, as seen in fresh condition in optical 

 section, in process of separation of the two layers, s.r.e., z.r.i., as 

 before. (Zeiss E, Oc. 2.) 



May 18, 1886. 

 Prof. W. H. Flower, LL.D., F.R.S., President, in the Chair. 



Mr. C. W. Rosset exhibited and made remarks on a series of 

 piiotographs taken during a recent visit to the Maldive Islands, and 

 gave the following account of his collections in these islands : — 



" On my return from an eighteen months' stay among the Veddas 

 of Ceylon, I undertook a journey to the Maldives, in October 188."), 

 in the course of which I passed seventy-five days on the Male Atol. 

 The principal object of my journey was to make a complete Ethno- 

 graphical collection, as also to take a series of photographs of the 

 people, objects and places of interest, and so on, and obtain full 

 particulars about habits and customs, manufactures, trade, &c. I 

 was also able to make a zoological collection. 



" I was not able to carry out my original plan, as the Sultan 

 absolutely refused to allow me to quit Male Atol, so that I was 

 unable to visit the southern islands of the group. It will therefore 



