412 THE AMEBIC AM NATURALIST [Vol. LI 



nest young before tliey are a week old, whicli is possible 

 only if the mother is tame enough to tolerate the dis- 

 turbance. In the first generations of our work we fre- 

 quently used tame Mus norvegicus females as foster 

 mothers. It is especially necessary to handle the young 

 from the very start at night, when they are very much 

 more active. Infinite patience is required for taming 

 these rats, far if once a young rat jumps from the hand, 

 which easily happens, as they are very nervous, it is im- 

 possible afterwards to induce it to remain on the hand. 

 It is possible to get the bigger species absolutely tame, 

 so that they will jump upon the owner's hand when the 

 cage is opened, that they will come to the hand if it is" 

 held out, will feed unconcernedly, will let themselves be 

 taken and restrained without resenting it, and that they 

 will not let themselves be disturbed by onlookers even in 

 mating. It is curious to note that they do not seem to 

 know their trainer. A tame rat is tame in respect to all 

 humans. It seems as if taming a rat takes away a good 

 deal of its nervousness, as tame rats are very much 

 quieter even if among themselves, and will breed in 

 smaller cages, and grow fatter than wild ones. 



Although we have had a good deal of experience in 

 taming nervous small animals we have never yet suc- 

 ceeded in taming the small house-rat, Mus concolor. 

 Even small blind nest young are so nervous that they 

 can not be induced to sit still in the hand without being 

 held. All we could do was to accustom the animals to 

 being restrained without resenting it. 



There is a very great difference in the disposition of 

 different species of rats, even in one closely related group 

 such as the Rattus group. The field-rats, Javanese as well 

 as Egj'ptian, and from Sumatra, behave like Mus norve- 

 gicus, they are reckless, timid and impulsive. An escaped 

 field-rat can be cauglit in a inoment, because it can be cal- 



along the wall-, and tlm- it can he ili-ivcn witlmut any 

 trouble into a ca.ue or catcliin.u- net. 



