SECONDARY SEXUAL CHARACTERS 



105 



Spiders, and Vertebrates. There are a few scattered 

 instances found in other groups, but they are rare. 

 In the lowest groups they are entirely absent, and are 



r- I- 



Fig. 52. — Four species of beetles in which the male (to the left) has horns 

 which are absent in the female tto the right). (After Darwin.) 



not found at all in plants; or rather, if character- 

 istic differences exist in plants, they are not called by 

 this name — for plants cannot see or move and there- 

 fore cannot court each other. 



