420 GENERAL ZOOLOGY 



In some members of the family the antlers remain simple 

 throughout life; in others they become much branched in 

 successive annual growths (Fig. 221). It is interesting to 

 note that, in a broad way, this was the order of development 

 of antlers in geological time, the earliest deer of which we 

 have any knowledge being without them. Horns and antlers 

 are used in the battles of the males for the possession of the 

 females, as well as for defense of themselves and their band. 

 The presence of these organs is usually ascribed to the ac- 

 tion of sexual selection. 



A large number of the ungulates have learned the ad- 

 vantage of cooperation and live in herds, which possess 

 an organized power of resistance far greater t.han any indi- 

 vidual has. In many cases, especially among the deer, scent 

 glands are developed on the head below the eyes, and as 

 the sense of smell is extremely acute, notice of the presence 

 of other members of the herd is given by the odor of the 

 secretion from these glands. Often the tail and rump are 

 conspicuously marked with white, showing plainly when the 

 animal is in flight, and probably serving as a recognition 

 or signaling mark. 



The structural peculiarities already referred to form the 

 basis for separating the ungulates into three divisions, — 

 those with an even number of toes, as the cow ; those with 

 an odd number of toes (one or three), as the rhinoceros and 

 horse; and the long-nosed forms (Proboscid'ea), including 

 the elephants. Of the even-toed ungulates the families of 

 camels (Cameridae), deer (Cer'vidae) and antelopes, goats, 

 sheep, and oxen (Bo'vidae) have the stomach (Fig. 222) 

 divided into a digestive and a nondigestive or storage 

 region, forming a complex organ of several compartments. 

 The food is taken into the first two of these divisions, the 

 reticulum, or honeycomb bag, and the rumen, or paunch, 

 where it remains till the animal has finished grazing and has 



