INTRODUCTION. 15 



hunters, against whom alone such farsighted prudence can 

 be directed, are much more modern than chamois ! 



As already pointed out, unchangeability is one of the 

 great characteristics of instinct, and further, it cannot and 

 must not blunder in guiding animals for their good. But 

 there are countless instances in which instinct not only 

 blunders, but is excessively changeable and subject to alter- 

 ation under changing circumstances and life conditions. 

 The fleshfly, whose maggots live on putrid flesh, very fre- 

 quently lays her eggs on the leaves of the Stapelia hirsuta^ 

 a plant which is sometimes cultivated in hothouses, and 

 which has an odor of putrifying flesh. And flies, in like 

 fashion, take rotten leaves for carrion, on account of their 

 smell, and lay their eggs therein, although in both these 

 cases their progeny must perish from want of food. Here 

 the animal is not led by instinct, but is misled by smell, 

 which, looking at the circumstance that it has been 

 born and bred among such smells, is not surprising. In- 

 stinct blunders in the same way, if, as Brehm relates 

 (" Animal Life," 2 ed., IX., p.' 16), the pine-moth, whose 

 caterpillars eat pine leaves, lays her eggs on oak trees 

 growing in the neighborhood of pines ; or when, as Brehm, 

 the father, (" Life of Birds," p. 247) has seen, a siskin 

 leaves its half-built nest, because it has found, during its 

 work, that the boughs of the tree on which it has built grow- 

 too closely, and do not give it room enough ; or when the 

 swallow takes wet street-mud for clay and builds therefrom 

 a nest of brief duration ; or when great waterbeetles fling 

 themselves with suicidal force against the glass of a hotbed, 

 thinking it water ; or when birds try to drink shining pots- 

 herds ; or when young birds, who are old enough to begin 

 to eat alone, chirp at the food in the hope that it will then 

 of itself come into their mouths ; or when grazing animals 

 eat poisonous plants with which they are unacquainted, etc., 

 etc. " In the valley of the Ahn," says the distinguished 

 clerical observer, Snell (" Zoological Gardens," vol. iv., 

 p. 61), " from Michelbach to Langenschwalbach, and in 

 some neighboring valleys, grows very plentifully the 

 stinking Hellebore, Helleborus fa'tidus. The sheep of the 

 neighborhood know very well the poisonous properties of 

 this plant, and never touch it, although they graze constantly 

 on the hills and cliffs where it grows. But as soon as 



