. Evolution and disease . Fig. 86.—a Dwarf Lemur {Microcchus siiiillii), showing thearrangement of the mammary glands. gray, or broad-nosed lemur {^Hapaleiuur griseus), has themammary glands situated on its arms.^ The above facts (with the exception of those relatingto Hapaleninr) seem to indicate that the lemurs havedescended from ancestors possessing two rows ofmamma;. In the dwarf lemurs, the abdominal pair ■ Beddard, Proc. Zool. Soc. ATAVISM. 165 have disappeared, whilst in the ring-tailed, black, andmongoose lemurs the pectoral pair alone persist. The persistence of the pectoral pair in t
. Evolution and disease . Fig. 86.—a Dwarf Lemur {Microcchus siiiillii), showing thearrangement of the mammary glands. gray, or broad-nosed lemur {^Hapaleiuur griseus), has themammary glands situated on its arms.^ The above facts (with the exception of those relatingto Hapaleninr) seem to indicate that the lemurs havedescended from ancestors possessing two rows ofmamma;. In the dwarf lemurs, the abdominal pair ■ Beddard, Proc. Zool. Soc. ATAVISM. 165 have disappeared, whilst in the ring-tailed, black, andmongoose lemurs the pectoral pair alone persist. The persistence of the pectoral pair in these lemursmay possibly be explained by the curious manner inwhich they carry the young. Lemur macaco has usuallyone at a birth, and this is carried about entwined aroundits mother in the manner represented in fig. 88. I havewatched the young lemur, and find that it rarely leavesits mother, and it is clear that whilst holding on in this. IlG. 87.—The arm oi llapaloiiur i^iiscus, sliowing itsbrachial mam nice. way it would be difficult for it to use the inguinal teats,if any existed, whilst it is within easy access of thepectoral pair. It seems to me reasonable to supposethat this habit of carrying the young has led to thepectoral teats being most used, and their gradualenlargement from increased use would slowly bringabout the suppression of the little used inguinal the nipples are present in the male, and havea disposition corresponding to that of the female. A review of the arrangement of the milk glands inmammals generally indicates that primitively they were 166 EVOLUTION AND DISEASE. arranged in two rows, extending along the ventralaspect of the trunk in both sexes ; and in situation theycorrespond to the course of the deep and superiorepigastric arteries, an extraordinary anastomosis effect-
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectabnormalitieshuman
