COURTSHIP AND SEX 209 



be interpreted in terms of the theory that she has a relatively 

 more anabolic constitution, and in terms of the fact that she 

 has to produce the eggs. Both interpretations require 

 careful handling since the two sexes are usually of approxi- 

 mately the same size, and the male is often the larger. 

 Hilzheimer notes for the male Gos-Hawk a length of 50-55 

 centimetres, for the female 36-40 ; for the weight of the 

 male Sparrow Hawk 150 grams, for the female 300 grams ; 

 and many similar figures might be cited. But approximate 

 equality is very common. 



After a survey of sex- characters, it is well to remind 

 ourselves that conspicuous difference between the sexes is 

 the exception, and general similarity the rule. In many 

 of the higher animals the males and females are very like 

 one another in external appearance. Cat, mouse, rabbit, 

 and hare may be mentioned among mammals ; rooks, king- 

 fishers, and many parrots among birds. Below the level of 

 crustaceans, in animals like starfishes and sea-urchins, 

 marine worms, thread-worms, jellyfish and corals, it is rare 

 to find more than minute sex-dimorphism. 



Contrariwise, although there may not be any marked 

 dimorphism, there may be a profound functional difference. 

 There are many facts, long since alluded to in " The Evolu- 

 tion of Sex " (1889), which go to show that in their meta- 

 bolism the male and the female are very different. They 

 run at different physiological rates ; the metabolism of the 

 male is relatively more intense. The ratio of katabolism to 

 anabolism is greater in the male than in the female. We may 

 quote a few sentences from another biologist, who seems to 

 take the same view. In his " Sex Antagonism " (1913), 

 Mr. Walter Heape writes : " The Male and the Female 

 individual may be compared in various ways with the 

 spermatozoon and ovum. The Male is active and roaming, 

 he hunts for his partner and is an expender of energy ; the 

 Female is passive, sedentary, one who waits for her partner 

 and is a conserver of energy." 



Perhaps the average differences between the sexes may be 

 summed up tentatively in this tabular contrast : 



p 



