388 ELEMENTARY ZOOLOGY 



istics of intelligence and reason man of course stands 

 immensely superior to all other animals, but both intelli- 

 gence and reason are too often shown by many of the 

 other mammals not to make us aware that man's mental 

 powers differ only in degree, not in kind, from those of 

 other animals. 



Pure instinct is hereditary, and purely instinctive actions 

 are common to all the individuals of a species. Those 

 actions which the individual could not learn by teaching, 

 imitation, or experience are instinctive. The accurate 

 pecking at food by chicks just hatched from an incubator 

 is purely instinctive. Purely instinctive also is the laying 

 of eggs by a butterfly on a certain species of plant which 

 may have to be sought for over wide acres, so that the 

 caterpillars when hatched shall find themselves on their 

 own special food-plant. Yet the butterfly never ate of 

 this plant and will never see its young. Such elaborate 

 instincts as these have been developed from the simplest 

 manifestations of sensation and nervous function, just as 

 the complex structures of the body have been developed 

 from simple structures (see Chapter XXIX). 



The feeding and domestic habits and the whole general 

 behavior of animals are extremely interesting subjects of 

 observation and study. And such observation intelli- 

 gently pursued will be of much value. The point to be 

 kept ever in mind is that all animal habits are connected 

 with certain conditions of life ; that in every case there is 

 an answer to the question "why." This answer may 

 not be found ; in many cases it is extremely difficult to 

 get at, but often it is simple and obvious and can be 

 found by the veriest beginner. 



Classification. The mammals of North America repre- 

 sent eight orders. Three additional mammalian orders, 

 namely, the Monotremata, including the extraordinary 

 duck-bills (Ornithorhynchns) and a species of Tachyglossus 



