( Ixviii ) 



of scales, sculpture, etc., ho proceeds as follows: — "These 

 dilferences are often complex and are strikingly con- 

 stant, but their utility is in almost every case problematical. 

 Fur example, many suggestions have been made as to the 

 benefits which edible moths may derive from their jirotective 

 coloration, and as to the reasons why unpalatable butterflies 

 in general are brightly coloured ; but as to the particular 

 benefit which one dull moth enjoys as the result of its own 

 particular pattern of dulness as compared with the closely 

 similar pattern of the next species, no suggestion is made. 

 Nevertheless these are exactly the i-eal difficulties that beset 

 the utilitarian view of the building-up of species. We knew 

 all along that species are aj>j)ro.vimately adapted to their 

 circumstances : but the difficulty is that wherever the differ- 

 ences in adaptation seem to us to be approximate, the differences 

 between the structures of species are frequently precise. 

 In the eai'ly days of the theory of Natural Selection it was 

 hoped that with searching the direct utility of such small 

 differences would be found, but time has been running on and 

 the hope is unfulfilled." At first sight there seems to be 

 something in these objections, but, in the first place, our know- 

 ledge of details is necessarily very small and cannot be 

 worked out in fifty or perhaps five hundred years with regaril 

 to individual species. In the second place, we may with leason 

 say that we have very much advanced in such knowledge ; 

 to refer to Mr. Bateson's own example, Lepidopterists will 

 tell us that the pattern of one dull moth may be of the 

 gi-eatest advantage to it in comparison with the closely similar 

 pattern of the next species, if its habits, the trees it rests on, 

 etc., are all taken into consideration. In the third place, the 

 very dissimilarity of individual examples of one cryptically- 

 coloured species (e.(j. the underside of Kallivia inachis) is of 

 itself a help to, as well as a px'oof of, adaptation to environ- 

 ment : in the case of cryptically-coloured moths or beetles too 

 much uniformity would evidently be a positive disadvantage 

 in the race for life. 



Moreover, the general facts of Mlillerian or synaposematic 

 mimicry afford a clear proof that it is only an approximate 

 adaptation as I'egards certain external details which is neces- 



