130 ROBERT M. YERKES 



by Hirschlaff (1905), and his tricks were interestingly described 

 from the pedagogical standpoint. 



Similar in character is Shepherd's (1915) brief description of 

 the stage behavior of Peter and Consul, both chimpanzees. It 

 is impossible to determine from the account whether these 

 animals are the same as were observed by both Witmer and 

 Hirschlaff. As no reference is made in Shepherd's paper 

 to other descriptions of the behavior of these animals and as 

 he adds nothing to what had already been presented, the reader 

 obtains no additional light on ideation. 



I have mentioned only samples of the articles on trained 

 anthropoids. All are necessarily descriptions of the behavior 

 of individuals who had been trained, not for psychological pur- 

 poses but for the vaudeville stage, and although such observa- 

 tions unquestionably have certain value for comparative psy- 

 chology, it is well known that unless an observer knows the 

 history of an act, he is not able to evaluate it in terms of intel- 

 ligence and is especially prone to overestimate its value as 

 evidence of ideation. 



There remain studies of the apes, dealing primarily with 

 behavior and mental characteristics, which are slightly if at all 

 experimental and deserve to be ranked as naturalistic accounts. 

 Such is, for example, the book of Sokolowski (19.08), in which 

 attention is given to the characteristics of young as well as 

 fairly mature specimens of the gorilla, chimpanzee and orang utan. 



The various pubHcations of Gamer (1892, 1896, 1900) deal, 

 especially with the language habits of monkeys and apes, but 

 observations bearing on ideation are reported. 



Wallace (1869) describes certain features of the behavior of 

 an infant orang utan whose mother he shot in Borneo. He 

 also reports observations concerning the behavior of adult orang 

 utans, many specimens of which were shot by him during his 

 travels. 



Early in the last century, Cuvier (1810) interested himself 

 in studies of the intellectual characteristics of the orang utan, 

 and his data, taken with those of Wallace, Sokolowski, and 

 others similarly interested in the natural history of mind, give 

 one a valuable glimpse of the life of the anthropoid ape. 



Finally, the data brought together by Brehm (1864, 1875, 

 1888) in his famous Tierieben; by Darwin (1859, 1871) in " The 



