AND AFFINITIES OF TARSIUS. 471 



animals of the same size as Lemurs tlie brain is about 1/lOOtli 

 (or less) of the body- weight, whereas in Lemurs it is usually 

 about l/70th, but may rise to l/60th or more. But in a monkey 

 of similar size it is l/20th or even 1/1 5th of the body-weight. 

 But we cannot on these grounds exclude the Lemuroidea from 

 the Primates, because the Tarsioidea are no better oft" than the 

 Lemurs so far as the quantity of brain is concerned. 



The remarkable claim has been made that all the resemblances 

 between the Lemuroidea and the otlier Primates were due to the 

 fact that the former are primitive mammals and the Tarsioidea 

 and Anthropoidea generalised creatures that have preserved 

 many primitive features ; or that they were the result of con- 

 vergence in animals leading similar modes of life. The foi'mer 

 statement can be ruled out of the argument at once, because the 

 brain of the Lemuroidea is definitely specialised in the manner I 

 have already described. Nor can the mode of life be regarded as 

 the exj)lanation of the likenesses, because such arboreal animals 

 as the Tree-Shrews, Squirrels, Galeojnthecus, et cetera, present 

 none of the numerous Primate features seen in the Lemur's brain. 

 The fashionable and seriously overworked doctrine of convergence 

 is also a mere evasion of the I'eal issue. There is abundant evidence 

 of convergence in the three Suboi'dei'S of the Pi'imates, but it is 

 clearly the expression of the tendency of similar traits to develop 

 in the various descendants of the same common ancestor, and 

 therefore can hardly help those who refuse to admit the close 

 connexion of the Lemuroidea, with the other Primates. Henry 

 Fairfield Osborn has emphasised the fact that " the same results 

 appear independently in descendants of the same ancestors''*. 

 ISTo more admirable illustrations of this principle could be found 

 than those elicited in the comparison of the Lemurs and Apes, 

 in the various individuals and species of which peculiar confor- 

 mations of brain, arrangements of muscles and arteries, form of 

 bones, structure of viscera and genital organs, which occur in no 

 other mammals, tend to reveal themselves in both the Lemurs 

 and the Apes. As illustrations of these striking demonstrations 

 I might refer to the central sulcus of Perodiciicus, the tendency 

 of the Sylvian fissure to fuse with the intraparietal, which is 

 found in j}^i/Giicebus and among the Apes in many of the Oebida? f. 

 Note also the striking likenesses in the temporal bone and the 

 course of the internal cai-otid in Tars'ms and the T^orisiformes, 

 the tarsus of the Galaginjeand Tarshcs, and the similar variations 

 in the lacrymal region of the skull in Lemurs and Apes which 

 Dr. Forsyth Major has described in the ' Proceedings ' of this 

 Society. These are, for the most pa,rt, illustrations of similar 

 peculiarities developed independently in divergent descendants 

 of the same common ancestor. 



* " The Fom- Inseparable Factors of Evolution." Science, N. S., vol. xxvii. 

 January 24, 1908, p. 150. 



f See mj' account in the ' Catalogue of the Museum of the Royal College of 

 Surgeons.' 



