AND AFFINITIES OF TARSIUS, 489 



between the Lemnroids and the Monkeys, but approaching mnch 

 more closely to the latter than to the former. 



The conclusions we have arrived at from the consideration 

 of the data of development may be summarised as follows : — 

 (1) The Lemuroids represent the basal stock from Avhich the 

 higher Primates evolved. They have retained in their develop- 

 ment many primitive Mammalian features, including a primitive 

 form of diffuse non-deciduate placenta. Development ally they are 

 free from marked specialisation, and they present us with a 

 developmental ground-plan of such a generalised type as to be 

 easily susceptible of such adaptive modifications as have occurred 

 in the higher tyjjes in the course of evolution. (2) The Tarsioids, 

 early separating from the primitive Lemuroid stock, were more 

 progressive. They show in their development the beginnings of 

 those adaptive changes which reach their culmination in the 

 Anthropoids, and by acquiring an early attachment to the uterine 

 wall tliey developed a localised deciduate placenta of the hiemo- 

 chorial type ; but for some reason, perhaps owing to a too active 

 participa,tion on the part of the maternal decidua, they failed to 

 exhaust its possibilities and to evolve an organ of the highest 

 possible efficiency. In many features of their development, they 

 are transitional between the Lemuroids and the Anthropoids, but 

 they are plainly on the Anthropoid line, and from them the 

 Anthropoids undoubtedly took their origin. (3) Starting from 

 the Tarsioid stock, already provided with the beginnings at least 

 of a hsemochorial placenta,, the Anthropoids went on to make the 

 most of their inheritance, and evolved a highly efficient type of 

 nutritive oryan in which the individualised villi are directly 

 ba,thed by the maternal blood — an efficiency which is reflected in 

 the advanced grade of organisation exhibited by the new-born 

 young. In t.hem and more particularly in the highest forms, the 

 Anthropoid Apes and Man, developmental adaption has reached 

 its acme, as witness the complete implantation of the early 

 blastocyst and the correlated development of a complete decidual 

 capsule ; and here I may be permitted to add, of the close genetic 

 affinity of Man and the higher Apes there can be no question on 

 embiyological ground s. 



Finally, as regards the systematic position of Tarsius, Hu- 

 brecht's contention that it nnist be removed from the Lemurs 

 I fully accept, but I am unable to agree that its tine position is 

 with "the Anthropoids. The remarkable annectant characters 

 which Tarsius exhibits justify lis in placing it, along with its 

 extinct allies, in a. subdivision of its own, and I am, therefore, in 

 agreement with those who, like Gadow and Elliot Smith, have 

 advocated, on quite other grounds, the division of the Primates 

 into three great radiations — call them what you may, — viz. a basal 

 or Lemuroid group, a Tarsioid group, and an Anthropoid group. 

 This tripartite arrangement seems to me most in accord with the 

 embryological data and best expresses the phylogenetic importance 



