1 6 INTRODUCTION. 



strange sheep, from a place where this poisonous plant does 

 not grow, come to Hohenstein, they eat it without suspicion 

 and poison themselves. Very many sheep bought in other 

 places have fallen victims in this way. There is then no 

 instinct warning the sheep ; they eat the flowers and flower- 

 buds of the hellebore, which are absolutely fatal to them, 

 more greedily than the leaves, which, as a rule, only make 

 them ill. This is the more noteworthy because the sheep 

 has not degenerated by being stall-fed, but lives in a half- 

 wild state." 



According to the same observer (" Zoological Gardens," 

 vol. iv., p. 60, etc.), dogs learn to know their food by ex- 

 perience, partly by instmction from the parents, partly by 

 their own attempts, or by tasting. When he threw to 

 his pigeons oats mixed with the, to them, unknown buck- 

 wheat, they eat only the first and left the other. But when 

 they had gradually and forcibly been habituated to the 

 latter, they learned to like it so much that they left the 

 oats and picked out the buckwheat. Newly caught birds 

 must at first have food they know mixed with the so-called 

 cage-food, or they will die of hunger in the midst of the 

 greatest abundance. Nay, each individual animal makes 

 his own experiments and his own discoveries in respect to his 

 food, and of this our observer brings a number of interesting 

 examples, and proves that certain single individuals are 

 able by example and imitation to rapidly spread habits ac- 

 quired in this way. 



That instinct, and even the strongest instinct, that of 

 food, can change in the most radical manner, is shown by 

 the example given by Dr. F. C. Noll ; a parrot, Nestor 

 notabilis, a native of the New Zealand Alps, which had 

 lived on flowers, and berries, and chiefly on insects, amused 

 himself with the meat barrels of the colonists, and then, 

 once accustomed to flesh food, took such a fancy to it that 

 he would not spare the sheep-skins hung up to diy, and 

 finally picked such big pieces out of the flanks of the living 

 sheep that the poor creatures died from exhaustion. Among 

 other things, as Brehm relates (" Animal Life," 2 ed., vol. 

 iv., p. 169), a flock of these birds pecked a sheep actually 

 to death by their united exertions, in order that they might 

 dine off it more comfortably. A similar fact is told by 

 Snell of a black cockatoo in Java, which learned to kill and 



