CHANGE OF HABITS IN ANIMALS 413 



and on a much greater scale than the somewhat similar 

 movements of Finches and Buntings, which in winter leave 

 the barren hedgerows for the bounteous farmyard. 



FAUNAS OF CIVILIZATION 



Changes of habit have been induced in individual animals 

 and species bythe seductions of man's cultivation and civilized 

 ways, but new and peculiar animal associations, or faunas on 

 a small scale, have actually been brought into existence 

 through his intervention. A couple of instances will illustrate 

 this curious creation of new worlds for some lesser organisms. 



THE FAUNA OF WATERWORKS 



It is notorious that the sewers of great cities harbour 

 armies of Rats, which feed upon the garbage underground ; 

 but many water supplies, also, have their own peculiar 

 tenants. Natives of the streams, or immigrants to the 

 reservoirs from which the water supply is drawn, find their 

 way, sometimes without disguise, sometimes in the form of 

 minute spores or eggs, into the pipes of the water system, 

 especially where filtration is deficient. In the pipes regular 

 colonies may thus be formed which live there year in, year 

 out, unknown to man, until their gradual accumulation forces 

 itself upon his notice by interfering with the water supply. 



It is scarcely to be expected that creatures so large as 

 vertebrates should form part of the waterwork's fauna. 

 Yet more than one household has been agitated at finding a 

 living Eel issue from its water-tap. Not long since, in fact, 

 the water-tap Eel was a topic of too frequent occurrence in 

 the London newspapers, and the persistence with which it 

 choked the pipes of the Hamburg supply led in 1886 to a 

 careful investigation of the animal content of that system. 

 A sieve-like apparatus was attached to the mains at various 

 points throughout the city, and the water was allowed to 

 pass with moderate force through this collecting apparatus, 

 with the result that the animals contained were filtered out. 

 The results were surprising. Worse than that, they were 

 remarkably uniform at each of the points examined an 

 indication that the haul was no chance capture but represented 

 a definite association of animals more or less constant 



