468 UN THE ZOOLOGICAL TOSITION 



which is found in no other Order, except in a somewhat modified 

 form in certain Ohiroptera and Edentata. This characteristic 

 fissure is found in all the Leinuroidea, and Anthropoidea, but in 

 Tarsias the enormous size of the orbits stretches the brain and 

 tends to erase this characteristic fold of the cortex. The great 

 expansion of the sensory and motor areas is responsible for the 

 development of the central sulcus in Perodicticus (see text-fig., 0) 

 and cei'tain of the Indrisinfe ; but in most of the Lemuroidea it 

 is represented only by two slight puckers or is absent altogether, 

 as in Tarsius, the Hapalidae, and some of the Cebidse (AoHcs and 

 CcdlitJirix). But this sulcus is so peculiarly distinctive of the 

 Primates that its occurrence in some of the Lemuroidea is of 

 the utmost value as an indication of the affinities of the Suborder. 

 The inferior frontal (text-figure, F.), superior temporal (T.), 

 lunate (L.), and orbital sulci complete the picture of the Primate 

 plan ; and they not only reproduce in the Lemuroidea the same 

 form and grouping as in the Cebidse (see text-figui'e), but are 

 subject to the same variations. Specially significant is the fact 

 that the postcentral (so-called " intraparietal") sulcus in JSfycti- 

 cehiis and some of the Indrisinte shows a tendency to fuse with 

 the Sylvian fissure, which produces the same peculiar pattern 

 that is found among the Cebidee in Chrysothrix, Aotus, Alouatta, 

 and at times in Lagothrix. 



Everyone who is acquainted. Avith the wide divergence between 

 the fissural pattern of the Primates and those of other Orders 

 cannot fail to be impressed with the completeness of the identity 

 between the Lemuroidea and the Anthropoidea in respect of 

 these features, and of its significance as positive evidence of 

 kinship. 



But these superficial resemblances are merely the outward 

 expression of a deep-seated structural and functional identity 

 Avhich demonstrates beyond any possibility of mistake that the 

 Lemurs are primitive members of the Order Primates. AV^orkiug 

 in conjunction with the late Dr. Page May and Professor W. H. 

 Wilson, I made an experimental examination of the reactions of 

 the cerebi'al cortex in Loris and Lemur *, and not only confirmed 

 the conclusions suggested by the study of the morphology of the 

 cortex, but also obtained results which showed a dift'erentiation 

 of cortically-controlled movements much superior to that of any 

 other mammals with the exception of the Anthropoidea. The 

 researches of Yogt subsequently (1906) confirmed our results. 

 But the evidence afforded by the minute structure of the brain is 

 even more decisive. In the ' Transactions ' of this Society some 

 years ago (May 1908, Vol. xviii. p. 175) I referred to my histo- 

 logical studies of the Prosimiaii cerebral cortex and their general 

 significance. Later in the same year the account was published 

 of a much more detailed examination of the Lemur's cortex than 

 I had made t. 



* See Report of the British Association, 1904, p. 760. 



f K. Bro(hnann, "Die cj'tosrchitektouische Cortexgliederuiig- der HalhafFen," 

 Journal fiir Psychologic uud Nourologie, Bd. x. 1908, p. 287. 



