580 
PEOF. W. TUENEE ON THE PLACENTATION OF THE LEMUES. 
c. That the villi are not uniformly distributed over the entire surface of the chorion 
in the Lemurs is no argument against the diffused character of the placenta ; for in 
none of the other specimens of the diffused placenta which I have examined (viz. the 
Pig, Mare, Orca, Narwhal, JBalcenoptera, Manis , and Dromedary) have I seen the 
whole surface of the chorion covered by villi. In the genera of Lemurs which 1 have 
here described, and in the additional genera Lepilemur , Hapalemur, and Cheirogaleus 
described by M. A. Milne-Edwards, a considerable surface free from villi, corresponding 
to the presenting part of the foetus, lay opposite the os uteri. In the Mare, Orca, and 
the Narwhal I have also seen a smooth surface of chorion bare of villi in this locality, 
which in the Narwhal measured 6 inches in one direction by 4 in another ; in Orca 
and in the Mare the bare patch was smaller in size. In my specimens of Lemur rujipes 
a bare surface was also found on the poles of the chorion situated in the uterine cornua ; 
but this is also a not unfrequent character in the diffused placenta, for I have seen it 
in Orca*, the Mare, and the Narwhal f. In the Narwhal the chorion occupying the 
non-gravid horn was bare of villi for about 5 inches from the pole, and even for a greater 
distance the villi were irregularly scattered, so that well-defined smooth patches could be 
traced as far as 10 or 12 inches from the pole ; whilst the end of the chorion in the gravid 
horn had smooth bands radiating for about 1 inch from the pole. In the pluriparous 
Pig, as was known to Yon Baer, the poles of the chorion are free from villi ; and in one 
animal which I examined I found a smooth non-villous surface extending for nearly 
3 inches from each pole. The smaller bare patches in the Lemurs situated amidst the 
villous surface are also not without their homologues in other forms of the diffused 
placenta. In the Narwhal smooth spots, varying in diameter from to inch, and 
surrounded by villous tufts, were occasionally situated on the villous surface of the 
chorion, and these spots were in apposition with smooth surfaces of the mucosa free 
from crypts. In the Pig numerous star-like spots, varying from \ to inch in 
diameter, were scattered over the surface of the chorion, and these spots were in appo- 
sition with smooth surfaces of the mucosa free from crypts. In the Mare narrow 
smooth bands of chorion were in apposition with smooth ridges on the uterine mucosa. 
In Lalcenoptera and the Dromedary I have also seen non-villous surfaces on the chorion, 
but the want of the uterus prevented me from localizing them in their relations to the 
mucosa. In Manis , as Dr. Sharpey pointed out, a band free from villi ran longitudinally 
along the concavity of the chorion, and there was a corresponding bald space on the 
surface of the uterine mucosa. 
d. The shortness of the villi and the shallowness of the crypts situated in the mucosa 
for their reception are characters common to all the examples of diffused placenta which 
I have examined. It is owing to this arrangement that the ready separation of the 
foetal placenta from the maternal can be effected, as the hand and fingers can be drawn 
out of a glove. 
* I have given a detailed description of the placentation of Orca gladiator in Trans. Eoy. Soc. Edinb. 1871. 
t An account of the placentation of the Narwhal is given in Proc. Eoy. Soc. Edinb. Feb. 1876. 
