154 PROCEEDINGS OF THE ACADEMY OF [Jan.. 



that similar processes, though not so well developed as in Gcdago, are 

 present in certain species of South American monkeys, as, for example, 

 in Lagoihrix and Mycetes. The presence of these processes is quite 

 as strong a proof that Platyrrhines have descended from lemurs as 

 are the peculiarities in the vertel^ral column already referred to that 

 man has descended directly from a lemur. It is well known that 

 while the supracondylar perforation of the humerus is not found in 

 any Old World monkey, nor in Hapale, Ateles or Mycetes among those 

 of the New World, nevertheless such perforation is found in the Cebida3 

 and most of the lemurs. It would be tedious to show in farther 

 detail that, as regards the muscular system, the character of the brain, 

 the larynx, the alimentary canal, and in many other respects, the 

 Platyrrhine monkeys are less specialized than the Catarrhines, whicli 

 has induced the majority of anatomists to regard the New World 

 monkeys as of higher rank zoologically than the lemurs, but lower in 

 the scale of life than the Catarrhines, occupying an intermediate posi- 

 tion between the two. This is consistent with the view that they 

 are the descendants of the one and the ancestors of the other. 



This conclusion has l^een confirmed in late years by the remarkable 

 researches of Selenka," Strahl,^" and others, who have shown, in a 

 general way at least, that the transitory stages through wdiich the 

 placenta of man and anthropoids pass are permanently retained as 

 the placenta of certain marsupials, lemurs, Tarsius, Platyrrhines, 

 Catarrhines, illustrating the law that in the development of the 

 placenta the ontogeny is as elsewhere the epitome of the phylogeiiy. 



Thus while in marsupials like Macropus the allantois remains free, 

 as first shown by Owen," and nearly fifty years afterward by the writer ,^° 

 in Perameles and Deisyunis the allantois, it is said, adheres to the 

 mucous wall of the uterus, forming at least the beginning of a placenta, 

 without, however, a decidua or chorionic villous process being devel- 

 oped. In lemurs, while no decidua is as yet developed, the chorion 

 exhibits villous processes which insinuate themselves into the mucous 

 wall of the uterus. In Teir-sius, however, the allantois begins to form a 

 true disk-like placenta with a veritable decidua — "nicht eine lockere 

 gross zottige diffuse Placentation wie Lemur und Nycticebus sondern 

 eine hoch komplicirte und diskoide Placenta besitzt."^^ 



^' Selenka, Studien iiber Entwickelungsgeschichte der Tiere, 1900, S. 176. ' 

 '^ Strahl, in O. Hertwig's Entivickelungslehre der Wirbeltiere, Dritte Lieferung, 

 1900, S. 235. 



19 Phil. Trans., 1834, 27. 



^°Proc. Acad. Nat. Sci. Phila., 1881. 



-1 HuBRECHT, Die Keimblase von Tarsius, 1896, S. 15. 



