194 THE ORIGIN I>F SPECIES 



progenitor of the ostrich genus had habits like those of 

 the bustard, and that, as the size and weight of its body 

 were increased during successive generations, its legs were 

 used more, and its wings less, until they became inca- 

 pable 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 seven- 

 teen 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 mutilations can be inherited 

 is at present not decisive; but the remarkable cases ob- 

 served by Brown-S^quard 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 bee- 

 tles 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 insects. 



In some cases we might easily put down to disuse 

 modifications of structure which are wholly, or mainly, 

 due to natural selection. Mr. Wollaston has discovered 

 the remarkable fact that 200 beetles, out of the 550 spe- 

 cies (but more are now known) inhabiting Madeira, are 

 so far deficient in wings that they cannot fly; and that, 



