932 LIFE : OUTLINES OF GENERAL BIOLOGY 



derived from the American Wild Turkey (Meleagris gallopavo), 

 which roosts in high trees. The wily farmer knew that the old 

 instinctive prompting was sure to assert itself. 



Why does a hen make such a fuss when she lays an egg ? It sounds 

 like an almost hysterically proud excitement; but it is obviously 

 open to the criticism that if the laying is in the open the cackling 

 advertises to possible enemies the whereabouts of the egg. The 

 plausible interpretation is historical. The domestic fowl is derived 

 from the Wild Jungle Fowl {Gallus hankiva) of India, a gregarious 

 bird of the forests. The flock moves about after food, and the 

 cackling is probably useful in making it easier for the hen, that has 

 been separated off during the egg-laying, to rejoin her companions. 

 Her call is answered, and she hears where they are. 



Ancient Tr.aits in Youth. — Beautiful instances of habit- 

 survival are seen in the play of young domesticated mammals, 

 e.g. kittens, puppies, lambs, kids, and calves. It has been shown by 

 Groos and others that playing among animals is of value as an 

 irresponsible apprenticeship to the serious business of life, and as 

 an opportunity for testing variations in habit before consequences 

 are too critical. Thus we understand why wild kittens and otters 

 should play at hunting and sham-fights, while wild sheep and goats 

 play at "Follow my Leader" and sham-races. Play is in some 

 measure the young form of work. But for many domesticated cats 

 that have given up hunting, and for most domesticated sheep that 

 have given up adventure, the playing activity has lost a great part 

 of its meaning. Yet it illustrates how the living influence of the 

 past may exert itself in youth, though weakening as the animal 

 reaches the age of discretion. 



As TO Habits and Habituation. — A frequent cause of obscurity 

 is the double use of the word "habit." When intelligently controlled 

 behaviour, such as playing an instrument or riding a bicycle, recurs 

 many times, it becomes easier and easier; it requires less and less 

 attention and control, it illustrates habituation. The transmission of 

 nervous impulses along certain lines becomes very easy, so easy 

 that the whole succession of steps may follow almost automatically 

 if the first one is taken. This is habit-forming in the strict sense ; it 

 is an individual acquisition — an automatisation — and thus an 

 economy — of what required, to begin with, much attention and 

 possibly much intelligent control. It is unfortunate that the same 

 word is often used for acquired longings and cravings, and desires 

 which we call "bad habits", and it is not less unfortunate that the 

 same word is used for the customs and ways of animals, as when we 

 say that Fabre devoted his life to studying the habits of insects. 

 These customary doings or ongoings, as they might be called, are 



