302 Studies in the Theory of Descent. 



nection between this phenomenon and simple 

 variability. 



In D. Hippophaes the process has either not yet 

 commenced, or is as yet in its first rudiments. If 

 we may trust the statements of authors, together 

 with the ordinary green form there occurs, rarely, 

 a silver-grey variety, which may be regarded as the 

 beginning of a process of colour substitution. 

 Among thirty-five living specimens of this scarce 

 species which I was able to procure, the grey 

 form did not occur, neither have I found it in 

 collections. 



In Macroglossa Stellatarum we see the trans- 

 forming process in full operation. A large number 

 of individuals (about thirty-five per cent.) are still 

 green ; the number of dark-coloured individuals 

 reaches forty-six per cent., these, therefore, 

 preponderating ; whilst between the two extremes 

 there are about nineteen per cent, of transition 

 forms, showing all possible shades between light 

 green and dark blackish-brown or brownish- 

 violet, and even, in solitary individuals, pure violet 

 (See Figs. 3 12, PL III.). The relatively small 

 number of the intermediate forms, taken in con- 

 nection with the fact that all the 140 specimens 

 employed in my investigation were obtained from 

 one female, leads to the conclusion that these 

 forms owe their existence to cross-breeding. It 

 would be superfluous to attempt to prove this last 

 conclusion with reference to the before-mentioned 



