344 



THE RISE OF ANIMAL LIFE 



Fig. 13-63. The African rhinoceros (Rhinoceros). The thick 

 armor-like hide and the two snout "horns" (not true 

 horns) provide this great beast with ample protection 

 against its enemies. 



short when compared to the plant feeders 



flippers which are effectively used in loco- 

 motion. They swim in a fish-like manner by 

 undulating motions of the body. Curiously 

 enough, the tail has dwindled to a useless 

 structure and the two posterior legs have 

 taken over its function. 



Seals come out on land, usually specific 

 isolated islands, during the breeding season 

 (Fig. 13-62). The males arrive first, and 

 when the females appear they gather as 

 many as they can about them and jealously 

 protect them within the family circle. 

 Should a female stray some distance from 

 the circle she is rudely retrieved. Males 

 battle ferociously for the females through- 

 out the breeding season and at its end they 

 go back into the sea, rather badly battered. 



In contrast to the carnivores are the her- 



(Fig. 17-7). In general, the carnivores are bivores, represented today by the domestic 



active and sometimes vicious animals, some horse and cow. The horse possesses an odd 



hunting in packs like the wolves and others number of toes ( Perissodactyla ) and the 



leading more or less solitary lives like the cow an even number of toes ( Artiodactyla ) 



big cats (Fig. 13-61). Man has made or "cloven" hoof. In their evolution, the 



friends with at least two members of the former came first and reached large sizes, 



group many centuries ago— the domestic as illustrated by the giant rhinoceroses 



cat and the dog. Although he has taken a 

 hand in changing the body form of cats by 

 selective breeding, his greatest efforts and 

 success have been with dogs. How success- 



that attained a shoulder height of 18 feet. 

 Those alive today are doomed to extinction 

 in spite of tlie fact that man has been able 

 to save the horse by domestication. Mem- 



ful he has been with his handiwork is well bers of this group have their weight borne 



illustrated by the many kinds of "man's best 

 friend." 



Some very interesting and bizarre carni- 

 vores are those that have taken to the water 

 in a serious way, with the result that they 

 have all but lost their ability to locomote 

 on land. These are represented by the seals, 

 sea lions, walruses, and others (Fig. 13-62). 

 They are relatively helpless on land but in 

 the water they compare favorably with the 

 best of die true aquatic forms, including the 

 fish. Having gone out on land long enough 

 to acquire the intelligence and cunning of 

 the mammals before returning to their orig- 

 inal environment, they should perhaps offer 

 considerable competition for the stupid 

 fishes. These animals are dog-like in many 

 respects. Their appendages have become 



on three toes in the case of the rhinoceros 

 (Fig. 13-63) or on one toe in the case of 

 the horse. The even-toed herbivores have 

 four toes, of which two bear the main 

 weight of the animal; this is illustrated by 

 cattle, sheep, goats, pigs, deer, elk and 

 many others. These have dominated the 

 previous group both in the past and pres- 

 ent. The present-day forms are the rumi- 

 nants or "cud-chewers." Their stomachs 

 have several compartments, a condition 

 which permits large amounts of hastily 

 acquired food to be temporarily stored and 

 then brought back into the mouth at a 

 later period to be properly chewed at the 

 animal's leisure. This is a most comfortable 

 and effective adaptation as well, since the 

 the animals might feed voraciously during 



