GENERAL LIFE OF MAMMALS. 531 



acteristically social. In the beaver village and among 

 monkeys there is combined industry, and their communal 

 life seems prophetic of that sociality which is distinctively 

 human. 



Among Birds, mates are won by beauty of song and 

 plumage ; Mammals not less characteristically woo by force. 

 Rival males fight with one another, and are usually larger 

 and stronger than their mates. The antlers of male deer, 

 the tusk of the male narwhal, the large canine teeth of boars 

 illustrate secondary sexual characters useful as weapons. 

 But manes and beards, bright colours and odoriferous glands 

 are often more developed in the males than in the females, 

 and may be of advantage in the rough mammalian court- 

 ship. At the breeding season, a remarkable organic reaction 

 often affects the animal, the timid hare becomes a fierce 

 combatant, and love is often stronger than hunger. The 

 courtship of Mammals is usually like a storm — violent but 

 passing ; for, after pairing, the males return to their ordinary 

 life, and the females become maternal. Some monkeys 

 are faithfully monogamous ; and exceptional pairs, such as 

 beavers and some antelopes, remain constant year after year ; 

 but this is not the way of the majority. 



The duckmole lays eggs and brings up her young in the 

 shelter of the burrow; the echidna has a temporary pouch. 

 In Marsupials the time of gestation is very short, and there 

 is no truly placental union between the unborn young and 

 the mother. When born, the young are very helpless, and 

 are in most cases transferred to an external pouch or 

 marsupium, within which they are nurtured. In Placental 

 Mammals the gestation usually lasts much longer than in 

 Marsupials, — its duration varying to some extent with the rank 

 in the mammalian series, but there are great differences in 

 the condition of the young at birth. " In those forms," 

 Prof. Flower says, " which habitually live in holes, like many 

 Rodents, the young are always very helpless at birth ; and 

 the same is also true of many of the Carnivora, which are 

 well able to defend their young from attack. In the great 

 order of Ungulates or Hoofed Mammals, where in the 

 majority of cases defence from foes depends upon fleetness 

 of foot, or upon huge corporeal bulk, the young are born in 

 a very highly developed condition, and are able almost at 



