BY JAS. P. HILL. 
581 
processes. The uterine mucosa is very richly supplied with blood, 
the maternal capillaries forming a network on and near the 
surface of the mucosa, so that foetal and maternal blood are thus 
brought into very close relation, readily allowing of transfusion. 
The allantois of Perameles is thus functional both as a respiratory 
organ and as an organ of nutrition — a distinct) advance upon the 
(according to Semon) purely respiratory function of the organ in 
Phascolarctus. 
In view of this discovery of a true allantoic placenta of the 
discoidal type in Perameles, the Marsupialia as a class can no 
longer be included among the Aplacentalia and the, up to this, 
universally recognised character of Marsupials " no allantoic 
placenta " likewise no longer holds good. 
The Macropod embryos available for examination consist of 
intra-uterine embryos of Macropus parma, M. ruficollis, M. robus- 
tus, and M. major. In this note it need only be mentioned that 
I am able to confirm Semon's belief that in the arrangement of 
their foetal membranes Macropods would be found to conform to 
his first type, as exemplified by Aepyprymnus, in which the 
allantois never comes into any connection with the serous mem- 
brane. 
I desire to tender my sincere thanks to Prof. J. T. Wilson for 
many valuable suggestions during the course of my work. 
EXPLANATION OF PLATE. 
Diagram of the foetal membranes of Perameles obesula. 
The ectoderm is indicated by a thin line, the mesoderm by a thick line, 
and the entoderm by a dotted line. 
Reference letters. 
all.c., allantoic cavity; all. St., allantoic stalk; amn., amnion; coe., extra- 
embryonic coelom; vies., mesenchyme of outer surface of allantois fused 
with mesenchyme of serous membrane; pro., prokalymma of Semon; s. t., 
sinus terminalis; ut, uterine wall; y.s., yolk sac; y.s.w., invaginated 
portion of yolk sac wall. 
