II.] INCIPIENT STRUCTURES. 39 



lion. lie says : " The ntlitudes of some insects may also 

 protect them, as the habit of turning up the tail by the 

 harmless rove-beetles (Staphylinida;), no doubt leads other 

 animals, besides children, to the belief that they can sting. 

 The curious attitude assumed l^y sphinx caterpillars is j)rob- 

 ably a safeguard, as well as the blood-red tentacles which 

 can suddenly be thrown out from the neck b}- the caterpil- 

 lars of all the true swallow-tailed butterflies." 



But, because manj' different kinds of animals can elude 

 the observation or defy the attack of enemies in a great 

 variety of ways, it by no means follows that there are any 

 similar number and variety of ways for attaining vegetable 

 food in a country where all such food, other than the 

 lofty branches of trees, has been for a time destroj^ed. In 

 such a country we have a number of vegetable-feeding Un- 

 gulates, all of which present minute variations as to the 

 length of the neck. If, as Mr. Darwin contends, the natural 

 selection of these favorable variations has alone lengthened 

 the neck of the giraffe by preserving it during droughts ; 

 similar variations, in similarly feeding forms, at the same 

 times, ought similarly to iiave been preserved and so length- 

 ened the neck of some other Ungulates by similarly pre- 

 serving them during the same droughts. 



(2.) It may be also objected, that the power of reaching 

 upward, acquired by the lengthening of the neck and legs, 

 must have necessitated a considerable increase in the entire 

 size and m;iss of the body (larger bones rec^uiring stronger 

 and more voluminous muscles and tendons, and these 

 again necessitating larger nerves, more capacious blood- 

 vessels, etc.), and it is very problematical whether the dis- 

 advantages thence arising would not, in times of scarcity, 

 more than counteibalance the advantages. 



For a considerable increase in the supply of food would 

 be requisite on account of this increase in size and mass, 

 while at the same time there would be a certain decrease 



