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Show 1888.] BROOD-POUCH OF RHINODERMA DARWINI. 235 contracted and asymmetrical; the orifices of the gular pouch are less modified than might have been expected (each is 7 m m . long), and the whole floor of the mouth differs in no respect from that say of a normal Cystignathus. The larynx (/, fig. 4) is situated far back, immediately behind a deep fold of the lining membrane of the floor of the mouth. Its mucous membrane was slightly swollen around the aditus; but there were neither epiglottis nor other accessory folds present, as might have been expected l. The brood-pouch of m y specimen contained 11 larvae, that number having been exceeded (12 and 15) by two of the five specimens dissected by Espada. These little animals are represented in fig. 2 Fig. 4. The floor of the mouth of Rhinoderma darwini, showing the tongue, larynx, and the orifices of the gular sac; multiplied two and a half times. as they lay in life; and it will be seen that they were, for the most part, irregularly disposed. Espada asserts that in one of his individuals the larvae (7 in number) were " einigermassen in zwei parallelen Reihen angeordnet " ; he does not state, however, in what way the surfaces of the bodies of these or any of his specimens were disposed respecting those of the parent. Examination of fig. 2 shows that, with the exception of two individuals on the parent's left, all lay with their ventral faces in apposition with that of the adult which bore them ; and it might appear from this that the larvae are carried on their backs. These, it will be seen, were far advanced in development and, with two exceptions, disposed with their heads towards the neck of the sac, as though making their way towards the exterior. From the positions in which they lay it is tolerably certain that attempts were made by them to gain the latter in their death-struggles; and I imagine that the parent died on its back, and that a stampede ensued, in which two of the unfortunate 11 prisoners were overpowered before righting themselves. The larvae were, as in one of Espada's examples, unequally advanced in development. In all, both fore and hind limbs were free, the latter being webbed in three instances. Five of the 11 were caudate ; and it is worthy of remark that those whose metamorphosis was 1 Cf. P. Z. S. 1887, p. 499, and Spengel, op. cit. p. 497. |
