WILD ANIMALS AS MAN'S ASSOCIATES. 529 



commenced to change its abode from cliffs to the more convenient and 

 protective eaves of barns. Professor A. E. Vcrrill, in a paper on this 

 subject in the " Proceedings of the Boston Society of Natural History " 

 (vol. ix, page 276), records numerous examples of their first appear- 

 ance about man's habitations in the East and West, and is inclined to 

 the opinion that, " when this continent was first settled by Europeans, 

 the cliff-swallow inhabited the whole of its breadth wherever there 

 were extensive limestone cliffs suitable for the building of its nests ; 

 and that as civilization advanced toward its native haunts, and suit- 

 able buildings became accessible to it, it gradually abandoned the 

 cliffs, and, increasing in numbers to a greater extent than before, on 

 account of the protection invariably furnished by man, it gradually 

 spread over New England and the other Northern States, where hith- 

 erto there had been no cliffs suited to its wants. In thus extending 

 its range it probably advanced both from the western and from the 

 northeastern parts of the country, both these regions abounding in 

 high limestone cliffs, which are entirely wanting in New England." 



A little more humanity on the part of boys, a suppression of the 

 bird-devouring instincts in the cat, and new birds will seek the com- 

 panionship of man. In Japan, owing to the gentle behavior of the 

 people, the crow has full liberty to go where he likes. As a conse- 

 quence, the densely populated cities swarm with the noisy fellows. 

 They repay the kindness shown them by acting as scavengers. Every 

 bit of organic matter, which in its decay might pollute the air, is seized 

 upon by the crows and devoured ; and thus it is that, by this and other 

 means, the death-rate in these large cities, under the hot sun of latitude 

 35, is lower than that of Salem, Massachusetts for example, in lati- 

 tude 42, with its reeking bodies of filthy water. With us the crow has 

 been driven away by constant hard usage, and now it is one of the 

 most wary of birds. In Japan, a crow that has no timidity will, on 

 the whole, get the most food for itself and offspring, and thus stand a 

 better chance of surviving and raising its progeny. Here the same 

 attribute would almost surely lead to its destruction. 



It is curious to observe how soon this fear in animals may be ex- 

 cited by the pressure of destructive agencies. More curious still is it 

 to note the fact that insects may be affected by it. I have repeatedly 

 observed that, in places where the common house-flies are undisturbed, 

 individual flies may be caught with ease. At Penikese Island I recall 

 this peculiarity as particularly marked. The movement of the hand in 

 the effort to catch them was invariably too quick. A friend of mine has 

 observed the same peculiarity concerning the house-flies in a country 

 church. They could easily be touched with the finger. It is plainly 

 obvious that the alert flies would be the ones to escape, and, thus sur- 

 viving, would perpetuate their peculiarities, while the stupid ones would 

 be the first to perish in any attempt to get rid of them. The house- 

 rat under the same selective action has, by continual survival from the 

 vol. xx. 34 



