168 EPPECTS OF USE AND DISUSE. [Chap. V. 



indeed inhabits continents, and is exposed to danger 

 from which it cannot escape by flight, but it can defend 

 itself by kicking its enemies, as efficiently as many 

 quadrupeds. We may believe that the progenitor of 

 the ostrich genus had habits like those of the bustard, 

 and that, as the size and weight of its body were in- 

 creased during successive generations, its legs were used 

 more, and its wings less, until they became incapable of 

 flight. 



Kirby has remarked (and I have observed the same 

 fact) that the anterior tarsi, or feet, of many male 

 dung-feeding beetles are often broken off; he examined 

 seventeen specimens in his own collection, and not one 

 had even a relic left. In the Onites apelles the tarsi 

 are so habitually lost, that the insect has been described 

 as not having them. In some other genera they are 

 present, but in a rudimentary condition. In the 

 Ateuchus or sacred beetle of the Egyptians, they are 

 totally deficient. The evidence that accidental mutila- 

 tions can be inherited is at present not decisive; but 

 the remarkable cases observed by Brown-Sequard in 

 guinea-pigs, of the inherited effects of operations, 

 should make us cautious in denying this tendency. 

 Hence it will perhaps be safest to look at the entire 

 absence of the anterior tarsi in Ateuchus, and their 

 rudimentary condition in some other genera, not as 

 cases of inherited mutilations, but as due to the effects 

 of long-continued disuse; for as many dung-feeding 

 beetles are generally found with their tarsi lost, this 

 must happen early in life; therefore the tarsi cannot 

 be of much importance or be much used by these in- 

 sects. 



In some cases we might easily put down to disuse 



