EFFECTS OF USE AND DISUSE. 120 



been caused by disuse. The ostrich indeed inliabits con- 

 tinents, and is exposed to danger from which it cannot 

 escape by flight, but it can defend itself, by kicking its 

 enemies, as efticiently as many quadrupeds. We may 

 believe that the progenitor of the ostrich genus liad 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 be- 

 came 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 speci- 

 mens 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 Egyp- 

 tians, they are totally deficient. The evidence that acci- 

 dental mutilations can be inherited is at present not de- 

 cisive; 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 con- 

 dition in some other genera, not as cases of inherited mu- 

 tilations, 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 insects. 



In some cases we might easily put down to disuse 

 modifications of structure which are wholly, or mainly duo 

 to natural selection. Mr. Wollaston has discovered the 

 remarkable fact that 200 beetles, out of the 550 species (but 

 more are now known) inhabiting Maderia, are so far defi- 

 cient in wings that they cannot fly; and that, of the 

 twenty-nine endemic genera, no less than twenty-three 

 have all their species in this condition! Several facts, — 

 namely, that beetles in many parts of the world are fre- 

 quently blown to sea and perish; that the beetles in Maderia, 

 as observed by Mr. Wollaston, lie much concealed, until 

 the wind lulls and the sun shines; that the proportion of 



