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 does _Phalangista_ occasionally at the present day. Hence to find remnants of both structures in existing mammals would not so incredible. This is what Dr. Klaatsch believes to be the case. In certain Ungulates, including two species of Antelope, Dr. Klaatsch found very considerable rudiments 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. 16), is a secondary teat; hence there is no difficulty in the comparison from this point of view. A pouch containing a primary {19} teat would of course be absolutely incomparable with a mammary pouch, because in that case the wall of the teat itself would be the pouch. Mammals belonging to quite different Orders show traces more or less marked of a marsupium. In young Dogs the teats are borne upon an area where the skin is thinner, the covering of hair less dense than elsewhere--all points of resemblance to the inside of the pouch of a Marsupial; in addition to this there are traces of the sphincter marsupii muscle. In other Carnivora there are similar vestiges. In _Lemur catta_ a more complete rudiment of a marsupial pouch is to be met with. In this Lemur the teats are both inguinal and pectoral; the skin in these regions is thin and but slightly hairy, and extends forwards as two bands of the same thinness and smoothness on each side of the densely hairy skin covering the sternum. This area is sharply separated from the rest of the integument by a fold which runs parallel to the longitudinal axis of the body, and can be comparable with nothing save the rudiment of the marsupial fold.