18 VESTIGIAL POUCHES CHAP. 
opens backwards is less disadvantageous to the contained 
young, 
The male Thylacine has a pouch which is quite or very 
nearly as well formed as in the female. There are also rudi- 
ments of a pouch in the male foetuses of many Marsupials, 
especially of those belonging to the Polyprotodont section of the 
order, though these rudiments are by no means confined to that 
subdivision. Up to so late a period as the age of four months 
(length 19°8 cm.) the male Dasyurus ursinus has a pouch. 
We have now to consider the interesting series of facts 
relative to the permanence—in a rudimentary condition it is 
true—of the mammary pouch in the higher Mammalia, facts 
which seem to be an additional proof that they have been 
derived from an ancestor in which the pouch was an organ of 
functional importance. The first definite proof of the occurrence 
of a pouch in any mammal not a Marsupial or a Monotreme was 
made by Malkmus, who found this structure in a Sheep. It 
seems, however, that the structures found in the higher mammals 
are not always comparable to the marsupium of the Marsupials, 
but sometimes to the mammary pouch of the Monotreme. That 
the Marsupials are a side line, and not involved in the ancestry 
of the Eutheria, is an opinion which is at present widely held. At 
the same time it is reasonable to suppose that the original stock 
lying between the Prototheria and the Metatheria, whence the 
latter and the Eutheria have arisen, preserved both the mammary 
pouch of the lower mammal and the marsupium of the further- 
developed stage, as docs Phalangista occasionally at the present 
day. Hence to find remnants of both structures in existing 
mammals would not be incredible. This is what Dr. Klaatsch 
believes to be the case. In certaim Ungulates, including two 
species of Antelope, Dr. Klaatsch found very considerable rudi- 
ments of folds provided with unstriated muscular fibre; there 
were in the adult Cervicapra isabellina a pair of pouches, one on 
each side, and a rudiment of a second on either side; possibly 
this multiplication of the pouches has relation to the number of 
young. That there is more than one pouch makes a comparison 
with the mammary pouch rather than with the marsupium 
probable. The Ungulate teat, it must be remembered (see p. 1 6),7 
is a secondary teat; hence there is no difficulty in the com- 
parison from this point of view. A pouch contaiming a primary 
