MENTAL LIFE OF MONKEYS AND APES 5 



on another monkey behind the wire screen. Figure 7 of this 

 plate indicates Skirrl in an interesting attitude of attention and 

 with an obvious lack of self -consciousness. The same monkey 

 is represented again in figures 8 and 9 of plate II, this time in 

 the act of using hammer and saw. 



All of the animals except the orang utan had been used more 

 or less for experiments on behavior by Doctor Hamilton, but 

 this prior work in no way interfered with my own investigation. 

 Doctor Hamilton has accumulated a large mass of the most 

 valuable and interesting observations on the behavior of monkeys, 

 and he more thoroughly understands them than any other ob- 

 server of whom I have knowledge. Much to my regret and 

 embarrassment in connection with the present report, he has 

 thus far published only a small portion of his data (Hamilton, 

 1911, 1914). In his most recent paper on "A study of sexual 

 tendencies in monkeys and baboons," he has given important 

 information concerning several of the monkeys which I have 

 observed. For the convenience of readers who may make use 

 of both his reports and mine, I am designating the animals by 

 the names previously given them by Hamilton. The avail- 

 able and essential information concerning the individuals is 

 presented below. 



List of animals in collection 



Skirrl. Pithecus iriis. Adult male. 



Sobke. P. rhesus. Young adult male. 



Gertie. P. irits-rhesns. Female. Born November, 1910. 



Maud. P. rhesus. Young adult female. 



Jimmy II. P. irns. Adult male. 



Scotty. P. irtts (?). Adult male. 



Tiny. P. iriis-rhesus. Female. Born August, 1913. 



Chatters. P. irus. Adult eunuch. 



Daddy. P. irus. i\dult eunuch. 



Mutt. P. irus. Young adult male. Born August, 1911. 



Julius. Pongo pygmceus. Male. i\ge, 4 years to 5 years. 



When I arrived in Santa Barbara, Doctor Hamilton was 

 about to remodel, or rather reconstruct, his animal cages and 

 laboratory. This gave us opportunity to adapt both to the 

 special needs of my experiments. The laboratory was finalh' 



