416 



GENERAL ZOOLOGY 



FIG. 221. Series of Antlers 



(American Museum of Natural 

 History) 



of these organs is usually ascribed 

 to the action of sexual selection. 



A large number of the ungulates 

 have learned the advantage of 

 cooperation, and live in herds, which 

 possess an organized power of resist- 

 ance far greater than any individual 

 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 mem- 

 bers of the herd is given by the odor 

 of the secretion from these glands. 

 Often the tail and rump are con- 

 spicuously marked with white, show- 

 ing 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 num- 

 ber 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 (Camel'idce), deer (Cer'vidce) 

 and antelopes, goats, sheep, and 

 oxen (Bo'vidw), have the stomach 

 (Fig. 222) divided into a digestive 

 and a non-digestive or storage region, 



