288 PROFESSOR ROLLESTON ON THE 
which a watch-shaped cavity is included, and each of which is sieve-like centrally from 
vascular perforations. 
The placenta (Pl. L. fig. 1) is thinnest at its centre; at its periphery the chorion is 
prolonged upwards in the shape of a circular rim (cu’) of a depth of a quarter of an inch. 
The umbilical vessels are very plainly seen to be prolonged into ramifications along this 
rim, and in it. The rim itself, or upgrowth, is continuous with the parapet, or down- 
growth, of uterine mucous membrane (uv Pp, Pl. L. fig. 3)—an arrangement which, so far 
as I have been able to find, is unique. 
The umbilical cords of these foetuses are long ; the foetuses being about an inch and 
a half long, the cord is in some instances of equal length with them; and the cavity of 
the amnios is large—sufliciently capacious, indeed, to admit of the introduction of a 
second foetus. Resembling the Human fcetus more or less in these two points, the foetal 
membranes of the Tenrec resemble those of the Ruminants in the possession of numerous 
corpuscles studding the interior surface of the amnios. These corpuscles are in some 
cases attached to the inner surface of the amnios, but in most cases they have fallen 
away from it ; in some cases they are filiform or even club-shaped, in most they are boat- 
shaped, or, rather, of the shape of a single valve of an ordinary bivalve, and attached 
by the concave side to the amnios, whilst projecting with a smooth convex one into its 
cavity. And as to the naked eye, so under the microscope, they resemble les plaques 
de Vamnios chez les Ruminants, as described by Professor Claude Bernard’. The longer 
of these corpuscles were as much as two millimetres long by one broad—much the same 
size, in fact, as the similarly placed corpuscles of the Elephant described by Professor 
Owen’; many, however, were of smaller dimensions. 
I could not discover any traces of yelk-sac, nor of allantois, nor of any membrane 
exterior to the amnios. Neither were any omphalo-mesenteric vessels detectable within 
the cavity of the abdomen. But the anastomosis between the veins of the abdominal 
wall and the umbilical vein, which is not rare in Mammalia®, was very plainly demon- 
strable. 
The placenta proper has assumed the ‘‘ flocculent”’ appearance which prolonged 
maceration, whether in weak spirits or in any other such menstruum, will confer on any 
placenta, however “‘ cellulo-vascular” or ‘‘ spongy,” in the normal condition. Still to the 
apices of its villus-bearing trees, shreds of the lamina (fig. 2) are in several instances 
left adhering, especially in the angle between the chorionic upgrowth, cu’, and the 
uterine aspect of the placenta. The layer of tissue adherent to the utero-placental area 
possessed histological characters quite distinct from those of the muscular coat it over- 
lay. The circular muscular coat is easily separable from the longitudinal. 
The lamina of tissue (fig. 2) intermediate between the placenta and the utero-placental 
area, I would propose (without any reference to the etymological meaning of the word 
* Brown-Séquard, ‘ Journal de Physiologie,’ vol. ii. p. 34, 1859. ? Phil. Trans. 1857, p. 348. 
* Rathke and Coste, cit. KGlliker, ‘ Entwickelungsgeschichte,’ p. 420. 
