130 SOCIAL HEREDITY AND SOCIAL EVOLUTION 



are, however, so clearly based on instinct that they 

 cannot be called in any sense families. Among the 

 vertebrates we find practically no family life until 

 we get to some of the very higher. Fishes show no 

 tendency to unite in families, though there are a 

 few cases in which the male parent has a watchful 

 care over the eggs produced by the female. Among 

 amphibians and reptiles there are no more indica- 

 tions of family life than among fishes. The method 

 by which the young are protected in these groups 

 varies somewhat, and occasionally the parent has a 

 more or less temporary interest in the eggs that are 

 produced; but there is no approximation to family 

 life. Among the birds there is the closest approx- 

 imation to the family that is found anywhere among 

 animals below man. Here, however, the indications 

 of family life are confined to the highest type of 

 birds. The majority of birds show no interest in 

 the young, and nothing approximating toward 

 the family. Among the higher birds, however, the 

 two parents remain together for a considerable 

 time, and continue associated until the eggs are 

 hatched, and then join in the care of the young. In- 

 stances of the interest of the father and mother 

 bird in their brood of young are too well known to 

 need any emphasis. Family life as shown here is 

 the closest approximation to the family life of man- 

 kind that is found anywhere. It is, however, inter- 

 esting and important to note that among birds this 

 family life is fleeting, and lasts only as long as the 

 young are helpless and require the care of the par- 

 ents. Among mammals in general the family life 

 is on a lower grade than it is in the birds. The 

 lower orders of the mammals, like the Rodentia 



