156 LEAVES FROM MY NOTE-BOOK. 



1894,* says that the conditions of artificial selection differ so 

 much from those of natural selection that it is difficult to carry on 

 experiments in artificial selection, which are biologically valuable ; 

 but in the case of the rats and cats in the " cold storage " ware- 

 houses of Pittsburg, natural and artificial selection have existed side 

 by side with results equally interesting, as showing the action of the 

 environment in modifying organisms. 



The thickly-furred rats above mentioned made themselves at 

 home in all the warehouses, and efforts were naturally made to 

 introduce cats, but at first in vain. The first cats turned into the 

 icy cold room pined and died. But advantage was taken, as is 

 usual in artificial selection, of a slight natural difference, and one 

 cat, which possessed unusually thick fur, proved not only able to 

 withstand the cold, but actually throve and grew fat. By careful 

 nursing a brood of seven kittens was raised in the rooms of the 

 Pennsylvania Storage Company, and developed into sturdy, thick- 

 furred cats, suited to an Icelandic clime. These original kittens 

 were distributed amongst the other " cold storage " warehouses in 

 Pittsburgh, and have been the progenitors of a peculiar breed of 

 cats adapted to the conditions in which they must find their prey. 

 Their tails are much shortened, and their hair is as thick and as 

 full of under fur as that of the wild cats of the Canadian woods. 

 But one of the most striking features in these cats, from a biolog- 

 ical point of view, is the development of the sensitive hairs on 

 the face, popularly called " feelers." In the ordinary cat these 

 sensitive hairs are about three inches long, but in the cold ware- 

 house cats they grow to a length of five and six inches. This is 

 a modification which has arisen de novo ; probably from that 

 condition of their environment, which obliges the animals to find 

 their prey in semi-darkness. There was, perhaps, a " predisposi- 

 tion on the part of the germ " in the mother cat, as Professor 

 Weismann would say, to grow thick fur ; but the germ does not 

 seem to have indicated any change in the feelers of the ancestral 

 pussy. 



The storage people state that if one of these furry cats is taken 

 into the open air, especially in summer time, it will die from con- 

 vulsions in a few hours. 



* << 



Limits of Biological Experiment," American Naturalist, Oct., '94, p. 845. 



