228 LOWER ANIMALS. 



females is accompanied by a corresponding difference in size, the 

 females being about one-half the size of the males. 



The deer is an animal not much different in size from the seal, 

 it is very active and, living where it is exposed to many enemies, 

 it has to be constantly on the alert for its own protection, but no 

 one would think of attempting to teach the deer such tricks as are 

 taught to seals, or any other tricks comparable to them. The deer 

 breeds at the age of 2, comes to maturity at 3, and may live to the 

 age of 20. 1S The average age of reproduction is, however, about 

 4 or 5 years as against 12 or 15 years for the seal. 



ELEPHANT AND HIPPOPOTAMUS. 



The elephant, owing to its huge size and strength, lives a life 

 comparatively free from natural enemies and, consequently, of 

 comparative peace, yet it is one of the most intelligent and sagacious 

 of all animals. It comes to maturity at about 30 years of age and 

 is said to live 150 years. It probably begins to breed at about the 

 age of 25, but I am not able to estimate the average age of repro- 

 duction. It must, however, be high. 



The nearest animal which I can compare with the elephant is 

 the hippopotamus, and that comparison is not very complete. An 

 adult hippopotamus is about 14 feet in length and girth. A young 

 one, about 10 months old, received in London was one-half this 

 length and girth and consequently about one-eighth the weight. 19 

 From this it would appear that the hippopotamus becomes adult 

 between the ages of 3 and 5. 



GUINEA PIGS AND WHITE MICE. 



Coming down to small animals, the Guinea pig may be said to 

 be anything but intelligent. It begins to breed at the age of 9 or 



(r8) American Cyclopaedia, Vol. VII, p. 75. 

 (19) American Cyclopaedia, Vol. VIII, p. 742. 



