MOEPIIOLOGT OF THE BKATX IX THE ^LA.MMALIA. 325 



in the cerebral lioinisplieres and the anatomy of the pyramidal tracts. But as these 

 data have no direct hcarinf? upon the subjects with which this memoir is chiefly concerned, 

 and would demand a much larger numl)er of illustrations to make their arrangement 

 intelligible than I dare ask for at present, I sliall defer their publication until some 

 other occasion. 



An investigation such as this, which aims at explaining th(! salient features of the 

 cerebrum in such a huge assemblage of animals as the Class Mammalia includes, must 

 entail many obligations. 



The unrivalled collection of mammalian brains in the Galleries and Stores of the lloyal 

 College of Surgeons were freely placed at my disposal by Professor Charles Stewart. 'I'o 

 Dr. Henry "Woodward, Dr. Charles W. .Vndrews, and Mr. Oldficld Thomas, I am indebted 

 for the opportunity of examining the large collections of mammalian crania in tbe 

 British Mviseum. Mr. W. L. H. Duckworth, in Cambridge, also freely permitted me to 

 make use of the considerable collection of mammalian brains in his possession. 



For valuable gifts of material for comparative purposes, I am under tlie greatest 

 obligations to Professor Howes, the late Mr. Martin "Woodward, Professors "Wilson and 

 Bahhvin Sjiencer and Mr. James P. Hill (Australia), Dr. Pobert Brown (South Africa), 

 Dr. Charles Hose (Borneo), and especially Captain Stanley Plower (Egypt), among many 

 others. "Without the rich (and I believe imprecedented) collection of representative 

 mammalian brains wliich I have thus been able to study, this communication would 

 have lost its only claim to consideration, l. e. that it truly sets forth the tendencies of 

 brain-evolution in the whole Mammalia, and not only in one small circumscribed group. 



For the facilities which have been so generously afforded me in the accomplishment 

 of this work I must express my great sense of indebtedness to all the gentlemen who 

 have a.ssisted me. 



The Cerebral HemlsphetvE ix the Genus Lemur. 



It is not necessary to describe the general form of the brain in the various genera of 

 Lerauroidea, because the bulk of tbe literature quoted above deals with this subject, and 

 certain of them, such as that of Gervais, are concerned exclusively with the shape of 

 the brain. ^Moreover, all the important features of the brain-form will be discussed 

 incidentally in these notes along with those peculiarities which are causally related to 

 the modilications in shape. 



When the dorsal surface of the brain of a Lemur is exposed by removing the roof of 

 the cranium, little else than the cerebral hemispheres can be seen. In front of the 

 pointed anterior pole of each hemisphere, the exposed area of the olfactoi-y bulb projects 

 very slightly more than one millimetre : and behind the broader, somewhat spatulate 

 caudal extremities of the hemisplieres in most cases only a very narrow band of the 

 cerebellum is exposed as a series of seven rounded knobs fringing the margins of the 

 hemispheres ((ig. 1). So that in order to study the relationships of the constituent 

 parts of the brain, it is necessary to turn to the examination of the ventral surface 

 (fig. 1). In front there is the broad flattened olfactory bulb, about 11 nun. long and 



