PEOF. W. TUENEE ON THE PLACENTATION OF THE LEMUES. 
585 
vascular tissue of the uterine mucosa are shed being effected through the cotyledonary 
placenta, in which the epithelial lining of the maternal cotyledons separates along with 
the foetal villi. I have also shown* that amongst the deciduate placentae, in the different 
genera and orders, considerable variations occur in the relative proportion both of the 
epithelial and subepithelial vascular tissue of the placental area shed during parturition. 
On the hypothesis which I have just advanced, that the more complex forms of pla- 
centa may have been evolved out of the more simple, the possibility that the Lemurs, 
notwithstanding the non-deciduate and diffused character of their placentation, may 
have been the stock from which the deciduate mammals had been derived does not 
present so many difficulties as are involved in the hypothesis put forward by Professor 
Haeckel. 
Explanation of Plates 49, 50, 51. 
For the series of coloured drawings in illustration of this memoir, which have been 
drawn with great care under my superintendence, I am much indebted to my former 
assistant, Mr. Alfked H. Young, M.B. 
Fig. 1. Posterior surface of the gravid uterus of Propithecus diadema. Natural size. 
Fig. 2. Posterior surface of the gravid uterus of Lemur rufipes. Specimen A. Natural 
size. f fecundated, and nf non-fecundated cornu ; o o, ovaries. 
Fig. 3. Outer surface of chorion from the gravid uterus of Lemur rufipes. Specimen A. 
Natural size. 
Fig. 4. Outer surface of chorion of Lemur rufipes. Specimen B. Natural size, f the 
pole in the fecundated cornu of the uterus ; nf, the pole in the non-fecundated 
cornu ; b, the bare surface opposite the os uteri. 
Fig. 5. Ovum of Lemur rufipes. Specimen C. Natural size. The chorion in the 
fecundated cornu has been cut through by a longitudinal incision, and the 
sac of the allantois opened into. V, the villous surface of the chorion at one 
pole ; am, the amnion, containing the foetus, seen through the layer of 
allantois which covers it ; al, the line of reflection of the allantois from the 
outer surface of the amnion to the inner surface of the chorion ; uv, vessels 
of the umbilical cord passing to the chorion; nf, the pole in the non- 
fecundated cornu. 
Fig. 6. The inner surface of the gravid uterus of Propithecus diadema after the removal 
of the foetus and its membranes, f, the fecundated cornu, the mucosa of 
which displays the sinuous folds and the depressed smooth areas described 
in the text ; nf, the non-fecundated cornu ; os, the fold of mucosa which 
marks the oS uteri ; Y, the vagina. Natural size. 
* Memoir on the Placentation of the Seals, in Transactions of the Eoyal Society of Edinburgh, 1875. 
MDCCCLXXVI. 4 M 
