CHILDHOOD AND YOUTH 3 



London Zoological Gardens, and shows the naked little creature, an 

 embryo rather than a young animal, hanging to a nipple inside 

 the hairy pouch of its mother. In higher mammals eggs are not 

 laid, and the young at birth are much more formed than in the case 

 of the kangaroo, but they may be covered with fur, have their eyes 

 open and be able to run in a few minutes, like young hares, or, like 

 young rabbits, may be naked, blind and helpless. Even in one 

 species there may be notable differences ; the kittens in a single 

 litter are seldom alike in size, in the degree of their development and 

 in the date when they 

 begin to see, and 

 although new - born 

 human babies are 

 more closely similar, 

 some may be at least 

 a month older or a 

 month younger than 

 usual, and yet grow 

 up quite normally. 

 These differences are 

 interesting and im- 

 portant, but I men- 

 tion them here only 

 to show that there is 



no exact, fixed point FlG . lt p art of the inner wall of the pouch of the red 

 in its history when kangaroo, with the young attached to the teat. 



. ,. . , , (Natural size.) 



a new individual 



ceases to be an egg or an embryo and may fairly be called a young 

 animal. 



In the same way the end of the period of youth is indefinite. Some- 

 times there is a sharp break. A caterpillar becomes a chrysalid and 

 from the chrysalid the full-grown moth or butterfly emerges. Some- 

 times, perhaps more often,, the transition is gradual. Even the time 

 when a young animal itself canbecome a parent does not give a dividing 

 line. A few generations ago, girls were thought fitted for marriage 

 when they were fourteen, and not infrequently became mothers 

 whilst they were still children. Amongst animals, parentage is 

 often precocious in individuals or in whole groups. We must be 

 content to take the period of youth in a general way as a subject 

 for description rather than for precise definition. 



Young animals can be placed in three groups, notably different in 



