Chap. VIII. THEIR DIFFERENCES. 321 



down ; but they are capable, according to M. Eobinet, 81 of again 

 crawling up the trunk. Even this capacity sometimes fails, for 

 M. Martins 82 placed some caterpillars on a tree, and those which 

 fell were not able to remount and perished of hunger ; they were 

 even incapable of passing from leaf to leaf. 



Some of the modifications which the silk-moth has undergone 

 stand in correlation with one another. Thus, the eggs of the moths 

 which produce white cocoons and of those which produce yellow 

 cocoons differ slightly in tint. The abdominal feet, also, of the 

 caterpillars which yield white cocoons are always white, whilst 

 those which give yellow cocoons are invariably yellow. 83 We have 

 seen that the caterpillars with dark tiger-like stripes produce 

 moths which are more darkly shaded than other moths. It seems 

 well established u that in France the caterpillars of the races which 

 produce white silk, and certain black caterpillars, have resisted, 

 better than other races, the disease which has recently devastated 

 the silk-districts. Lastly, the races differ constitutionally, for some 

 do not succeed so well under a temperate climate as others ; and a 

 damp soil does not equally injure all the races. 85 



From these various facts we learn that silk-moths, like the 

 higher animals, vary greatly under long-continued domes- 

 tication. We learn also the more important fact that varia- 

 tions may occur at various periods of life, and be inherited at 

 a corresponding period. And finally we see that insects are 

 amenable to the great principle of Selection. 



81 'Manuel de l'Educateur,' &c, p. 12, 209, 214. 



26. 84 Robinet, * Manuel/ &c, p. 303. 



82 Godron, « De l'Espece,' p. 462. 85 Robinet, ibid., p. 15. 



83 Quatref'ages, 'Etudes,' &c, pp. 



15 



