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REPRODUCTION OF ANIMALS 



gametes from those that produce female gametes. Among the 

 frogs, fishes, and other lower animals, there is little external mor- 

 phological difference in sex, but the higher species of animals show 

 external differences. In addition to the structures that are directly 

 related to producing and discharging gametes, distinct character- 

 istics are found in other parts of the body. The males of many 

 species of birds can be easily recognized by the crests on the heads 

 and spurs on the legs. The male birds are usually more gayly 

 colored and have sweeter songs than the female birds. 



Among many mammals (animals that are warm-blooded, 

 covered with hair, and suckle their young) , there are usually differ- 

 ences in horns, size of body, habits, voice, temperament, and in- 

 terests. Contrast the male reindeer with the doe. The male is a 

 huge animal with tremendously large antlers. He is a vicious 

 fighter and protects the doe. She lacks antlers, is proportion- 

 ately small and slender, and usually depends upon the male for 

 protection. The differences just noted are called the secondary 

 sexual characters of reindeers. 



Spawning of frogs. Fertilization takes place in animals in a 

 way very similar to plants. The gametes mature and are then 

 brought together in a way peculiar to the organism. Different 



.V. Y. Xo'&tog ic.il Xoc. 



The lioness and lion show interesting secondary sexual characters. Note the huge head and 

 shaggy mane of the lion. 



