MAMMALS WITH CONTRASTED . COLOURS 139 



What I have said is enough, I think, to prove that this hght 

 theory is wholly untenable, at least as far as mammals are con- 

 cerned.^ 



The reader might however say, Have you any other theory to 

 substitute for the light theory ? 



Yes, I have, and it is this : I have endeavoured to show that 

 the spots and stripes of mammals are in many cases pictures of 

 ancestral armour-plates, modified subsequently in hundreds of ways 

 in some, or wholly obliterated in others. : 



Well, the same theory of descent from armour-plated ancestry 

 will explain why there is on the flank of many animals that sharp 

 line of demarcation between the dorsal and the ventral colouring. 

 That sharp longitudinal line indicates the margin of the ancestral 

 carapace, as we see it in the Armadillo, the Glyptodon, the Pango- 

 lin, and others. 



Curiously enough, the little Armadillo of Argentina {Chlainy- 

 dophorus truncatus') has its armadilloid armour sharply truncated 

 posteriorly, and its rump is patched up by a differently plated 

 perpendicular shield. This curious appendage, according to my 

 view, might perhaps account for that white patch which so many 

 ruminants have behind, the line of demarcation between the dark 



^ I am aware that in the cases of peaches, apples, pears, etc. , light colours their cheeks, 

 and I have seen a peach, partly shaded by one leaf, not acquire colour under the leaf. 

 But I am also aware that round the stone of certain peaches there is the same red colour 

 we see on their cheeks, while the intermediate thickness (-sarcocarp) is either white or 

 yellow, and this central redness could not be produced by light in its ordinary sense. 

 Then there are the purple aubergines, which acquire their intense colour also on the 

 shaded sides. And I have been informed by a noted horticulturist that he has seen 

 the black Hamboro' grape beautifully coloured when the roof of the house was almost 

 wholly shaded by the leaves. He also told me- that he has seen the red seakale and the 

 red rhubarb grown in total darkness, and the tips of their leaves nevertheless always 

 acquire a red tinge. Moreover, we do not see the sweet-water grape colour, although grown 

 outside and fully exposed to light. I think if we substitute electricity for light, acting on 

 certain chemical ingredients, we may perhaps be nearer the right explsination. 



