1904.] NATURAL SCIENCES OP PHILADELPHIA. 155 



The placenta of the New World monkeys exhibit a step further in 

 advance the difference from the placenta of Tarsius, being however, 

 one of degree raiher than of kind. 



In the Old World monkeys the allantois forms a double placenta, a 

 primary large dorsal one and a secondary small ventral one (Plate X). 

 While this appears to be normally the case, it should be mentioned 

 that the writer observed but one placenta in the case of a pregnant 

 female of Macacus cynomolgus examined by him, though the preg- 

 nancy was far advanced in both instances. ^^ n ^m j^q observed that 

 in the case of the Macacus (Plate X), the two placentas are not 

 entirely separated as is usually the case in Catarrhines, being joined 

 by a small body of tissue. 



It is also a significant fact that while two umbilical veins and two 

 umbilical arteries are always present in the umbilical cord of the New 

 World monkeys, but one umbilical vein is present in that of the Old 

 World ones. Finally, the placenta of the anthropoids agrees essentially 

 with that of man. 



In the opinion of the writer, therefore, the phylum submitted at 

 p. 149, essentially that of Haeckel," expresses about the truth as to 

 the descent of man, etc., so far as can be learned at present from the 

 facts of palaeontology, comparative anatomy and embryology, that 

 bear upon the question. That the ancient Prosimise, Hyopsodinse, 

 Adapida?, etc., have descended from some ungulate type of life is 

 manifested by their affinities with the latter group of mammals. 

 Indeed, Cuvier described .4c/apis as "un autre genre de pachyderme 

 — et que je nommerai provisoirement Adapis,"^* while, according to 

 Leidy, Notharctus tenebrosus was "a, small extinct pachyderm, re- 

 sembling that of some of the existing American monkeys quite as much 

 as it does that of any of the living pachyderms. "^^ 



It is quite possible that future researches may show that there is 

 no genetic connection between Chiromys and the Rodentia, but that 

 the rodent-like teeth of the former and of the wombat may have been 

 acquired independently by a process of natural selection, it being easy 

 to see, according to Tomes,^^ ''how a rodent type of dentition is bene- 

 ficial to its possessor by rendering accessible articles of food wholly 

 unavailable for creatures which have no means of gnawing through' a 



" Proc. Acad. Nat. Sci. PMla., 1879, p. 146. 

 ^^ Anthropogenie, Zweiter Band, 1903, S. 650. 

 ^■^ Ossemens Fossiles, Tome 5"'', 1S35, p. 460. 

 ^^ Leidy, op. cit., pp. 86, 89. 

 2« Op. cit., p. 249. 



