ON THE ARRANGEMENT OF THE FCETAL MEMBRANES IN THE CETACEA. 485 



was seen to consist of cells, the great majority of which were circular in form, 

 and had a yellowish colour. The smallest of these cells were of the size of lymph- 

 corpuscles, but as a rule they were twice as large. Most of the cells contained 

 a single nucleus, but some possessed two or more, and in a few instances large 

 brood cells were observed, packed full of nuclei, or young cells. Some patches 

 of small hexagonal cells, fitted together by their margins, like the cells of the 

 choroid coat of the eyeball, were also seen ; and it is possible that these cells 

 formed a pavement epithelium for the cavity in which the brown pultaceous 

 mass was contained. (Fig. 9, Plate XVII.) These bodies, like the amniotic cor- 

 puscles already described, were developed in relation to the attached surface 

 of the amnion, but, unlike the majority of the latter, had not projected so as 

 to assume a pedunculated appearance. In all probability they and the amniotic 

 corpuscles have common morphological relations, though what their function 

 may be it is not easy to determine. 



Position and Form of the Foetus.— The foetus, a male, enveloped in its 

 membranes, occupied the left uterine cornu. It lay with its beak directed 

 towards the corpus uteri and os internum. The caudal end was curved forward 

 under the abdomen, so that the flanges of the tail were in close relation to the 

 penis (Plate XVIII. fig. 16). The curve of the back of the foetus corresponded 

 with the convex anterior surface of the uterine cornu. In its position in utero, 

 therefore, it closely corresponded with that of a foetus of Globiceps, figured by 

 Van Beneden,* and it bears out the opinion entertained by that naturalist, that 

 the foetus in the cetacea is born with the beak foremost. The foetus possessed 

 the external characters of the genus Orca. The beak was not so pointed as in 

 Delphinus, or so truncated as in Globio-cephalus ; the falciform dorsal fin 

 lay in the same transverse plane as the umbilical cord ; the pectoral fins 

 were broadly ovoid, flattened on the surfaces, with a rounded anterior and 

 sharp convex posterior border. The colour was dark-slate on the dorsum 

 of the head, back, tail, and upper part of the sides of the body. A 

 distinct pale patch extended horizontally backwards immediately above and 

 beyond the eye slit. The under surface of the lower jaw, throat, and the 

 entire ventral surface to a little beyond the anus, were also pale, and a 

 patch continuous with the ventral surface commenced in front of the penis and 

 extended upwards and backwards along the side of the body. The under 

 surface of the tail was also pale. In the adult these pale patches and surfaces 

 are white, which, contrasting strongly with the otherwise dark colour of the skin, 

 give to the animal a characteristic black and white piebald appearance. But in 

 the foetus, from the comparative thinness of the cuticle over those surfaces where 

 it was devoid of pigment, the pale patches, instead of being white, were salmon- 

 tinted, owing to the colour of the vascular cutis being transmitted through the 



* Bulletins de TAcad. Royale de Belgique, 2d Series, xx. No. 12. 



