﻿Dec, 1856.] 



ELLIOTT SOCIETY. 



65 



But I will now proceed to describe this metamorphosis in as 

 detailed a manner as my observations for the past summer permit 



EMBRYONIC DEVELOPMENT, 



The earliest condition of the ovum of Turritopsis nutricula, 

 which has come under my observation, is that of an ellipsoid cell, 

 very small, and of faintly granular content, without any definite 

 nucleus. The next stage is that in which the germinal vesicle, and 

 dot have appeared. The ovum now increases in size, and, at this 

 stage, I have observed the yolk to be more distinctly granular, and 

 the gerrninative vesicle to be itself a n ucleolated ceil. After this, 

 the granular yolk becomes denser, apparently by the multiplica- 

 tion of granules, and almost opaque, the germinative vesicle has 

 disappeared, and the centre of the egg is occupied by a translu- 

 cent, ill-defined circular or oval nucleus, which is, perhaps, the 

 clear oil globule known in ripe ova. Beyond this, I have not ob- 

 served. The segmentation, after impregnation, still remains to be 

 seen, as well as all the consecutive stages. The gradual growth 

 of contiguous ova now produces compression, .and the curvilinear 

 outline is variously modified into more or less irregular rectilineal 

 figures, some being even hexagonal, while others assume an elon- 

 gated form rounded at one extremity, and pointed at the other, 

 (Vide PI. 5, rT. 16, 17, 18.) These I have never seen greatly elon- 

 gated. A figure by Prof. Forbes, of the ova of Turris negkcta 

 (Brit. Nak. Med. PI. 3, fig. 2, €.) shows that a long process maybe 

 developed from the sharp extremity of this ovoid embryo, which, 

 in all probability, takes place in the generality of cases within the 

 ovary. I would have supposed this to be the incipient proboscis of 

 the larva, but the observations of Gosse show that, in Turris ne- 

 gkcta, the eggs fall and produce elongated root-.like appendages, 

 which become fixed before the hydra shoots from the body of the 

 germ mass. It is, therefore, probable that this process is such an 

 incipient radix. No phasis like this is in any manner indicated in 

 the ova of Turritopsis. 



Notwithstanding my good fortune in having had specimens of 

 Turritopsis alive in water many times since the 10th of June of the 

 past year, I have never been so fortunate a-s to observe the expul- 

 sion of the ova, and cannot, therefore, say whether they make their 

 exit by the mouth or otherwise. But I think it may be safely be- 

 lieved that they pass out either by the mouth or by some openings 

 immediately in its vicinity, perhaps on the labial fimbriated border 

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