EARLY DAYS AND EARLY WAYS 9 



dition, and, as a rule, before the eyelids have opened, 

 and while the body is yet naked, or but scantily clothed. 

 Yet there are degrees of helplessness, and of nakedness, 

 which is as much as to say that the period of birth is 

 hastened or retarded in accordance with the needs of the 

 environment. The rabbit and the hare furnish a very 

 good illustration of these differences, and the conditions 

 which apparently govern them. In the rabbit the young 

 are prematurely born, so to speak, before the eyelids 

 have opened, or the hair has thrust its way through the 

 skin. The birth of the young hare, on the other hand, 

 is retarded until a further stage of development has been 

 reached, so that it is ushered into the world with open 

 eyes, and a thick coat of fur. But mark the different 

 conditions which obtain in the two cases. The young 

 rabbit is born in a warm and sheltered burrow, the young 

 hare above ground. The rabbit, for some considerable 

 time, is shielded from enemies ; the hare, on the other 

 hand, knows no such security, and its retarded birth has 

 therefore hastened the time when it will be able to escape 

 danger by flight. For the moment, the maternal care 

 in distributing her litter over a fairly wide area, and the 

 hkeness in coloration between the young and their sur- 

 roundings, have to suffice ; and as a matter of fact they 

 suffice very well, or hares would be less plentiful. 



That there are considerable differences in the birth 

 periods of the marsupials and the rodents, for instance, 

 there can be no question. In other words the birth 

 period is, as we have already remarked, not a common 

 standard of measurement : what are post-natal stages of 

 development in the one case are pre-natal in the other. 

 And this fact will become the more apparent if com- 

 parison is made between the young of several dissimilar 



