296 DR. A. KEITH ON THE CHIMPANZEES. [Mar. 7, 



1. Ou the Chimpanzees and their Relationship to the Gorilla. 

 By Arthur Keith, M.D., P.Z.S. 



[Eeceived March 7, 1899.] 



(Plate XX.) 



At the present time there is in the Menagerie of Messrs. 

 Barniim and Bailey an adult female anthropoid ape, known by the 

 name of " Johauna," regarded by its owners as a Gorilla, but which, 

 tliere can be no doubt, is in reality a Chimpanzee. No difficulty 

 has ever been experienced in distinguishing between the male 

 Gorilla and the male Chimpanzee, nor between the females when 

 an anatomical investigation has been possible ; but on several 

 occasions, as in the case of this Ape, living female Chimpanzees 

 have been mistaken for Gorillas. There is the classical case of 

 " Mafuka'" ^ of the Di'esden Zoological Garden. " Joh.anna" shares 

 all the features of "Mafuka"; she answers to the description 

 given by Du Chaillu of the species he names " Troglodytes hooloo- 

 kamha"'^. The animal dissected and described by Gratiolet and 

 Alix ^ under the name of T. aubryi was also of the same variety. 

 " Johanna " is of interest because she represents a variety of Chim- 

 panzee which approaches the Gorilla in so many points that it is 

 evident the characters which separate the two African anthropoids 

 are not so well marked as many suppose. The difficulty of distin- 

 guishing the one from the other, as shown by a recent communica- 

 tion by Mr. Duckworth^ to this Society, is such that it has become 

 necessary to sum up, from a much w^der examination of material 

 than has ever been at anyone's disposal before, the structural and 

 physiological differences Mhich separate the Gorilla from the 

 Chimpanzee, and at the same time to sum up the evidence as to the 

 existence of one or more species of Chimpanzee. Some five years 

 ago, on M'orking minutely over all the anthropoid material in the 

 collections of the Natural History Museum at South Kensington 

 and the Museum of the Eoyal College of Surgeons, which contain 

 the skulls of 31 Gorillas, 44 Chimpanzees, 73 Orangs, and 

 56 Gibbons, I was struck by the fact that nearly all the characters 

 which had been used to differentiate species were points which 

 varied in structure and form with age, sex, and the individual, 

 but I have never had any difficulty in distinguishing between the 

 skulls, even of foetal Gorillas and Chimpanzees. 



1 . The Eruption of the Permanent Teeth in Chimpanzees. 



Mr. Duckworth has promised the Society a full description 

 of " Johanna," but I learned certain facts from her keeper, 



' Keith. ' Introduction to the Study of Anthropoid Apes,' pp. 8, 23. 

 London, 1897. 



^ Du Chaillu. ' Explorations and Adventures,' ISfil, p. 360. 



^ Gkatiolet at Alix. " Recherclies sur I'Anatoiuie dn Troylodytes aubryi," 

 Isouv. Archiv. du Mus. Hist. Aat. 18(i6, t. ii. pp. 1-203. 



•» W. L. H. Duckworth. P. Z. S. 1898, p. 989. 



