specific modifications of Japan Carabi. 523 



about the Drypta and Balaninus, and that they are such 

 as should be brought forward ; but do they cover the 

 conclusions ? I am merely applying to details in struc- 

 tural and other peculiarities what we learnt in our child- 

 hood : an eye is for seeing, an ear is for hearing. If we 

 are frustrated in an effort to discover why a glowworm is 

 phosphorescent, let us examine a May-fly (Teloganodes) , or 

 a centipede, which is luminous, and if we discern a reason 

 for its existence in either one or the other, it will lead 

 us to the cause in all. If we say a leg is for walking 

 we err ; we must say a leg is for moving. If we see a 

 brown beetle clinging to brown bark, we do well to say 

 the brownness in both arises from the same cause ; but if 

 we believe in the protective colour theory, we must say 

 that one of the primary uses of the clinging foot to a 

 brown beetle is, to enable it to cling close to bark where 

 its concoloration will enable it to escape extermination. 

 I believe the clinging tarsus is an independent modifica- 

 tion arising from habit, and that colour is a modification 

 dependent on that structure only so far as it will come 

 to any creature which will inhabit similar situations. 



In colour, let me give three more examples : a leaf, a 

 Sphinx larva, and Cassida viridis. Light affects these in 

 the same way, or nearly so, because they are. not very 

 dissimilar in substance, when considered merely in their 

 relation to light. Certain light-rays can pass through 

 them in a similar way, for they are translucent, and this 

 causes a sameness of colour. The Cassida's body is 

 black, for it is of a different texture to its case. In 

 Ceylon, and in other places, are certain Eeptilia, snakes, 

 frogs, and lizards, which possess skins of marvellous de- 

 licacy ; they are semitransparent and admit certain light- 

 rays to pass through them ; their whole physiological 

 structure, too, is such that light is admitted into their 

 material substance ; they sit on foliage, where they are 

 exposed to all the waves of solar-rays and heat, just as 

 leaves are, and they are green. But remove them to a 

 trunk, shaded, or partially so, from the direct rays of the 

 sun, and the reptiles become mottled or brown, as the 

 case may be, for their mutations are too variable to de- 

 scribe ; their colours differ at each hour of the day, and 

 are affected by almost every passing cloud. Their 

 material substance is such that they become green 

 where Cassida viridis is green, and mottled where a 

 Noctua is mottled. 



