20 ANIMAL COLORATION. 



to the distribution of the underlying nerves. Mr. Allen has 

 stated* that the white marks on the head of the tiger correspond 

 to the area of distribution of the infra-orbital nerves. The 

 nerves terminate in or near the skin; and it is clear that there 

 must be some connection between nerve supply and coloration, 

 from the fact that in a hedgehog whose spines were white, the 

 nerves in connection with the muscles for contraction of the skin 

 were greatly diseased.! There are plenty of other pathological 

 facts of a like nature. 



Changes of Colour during Lifetime. 



Many animals which are hatched from eggs deposited by 

 the parent undergo a more or less elaborate series of changes 

 before they acquire the adult form. The most familiar 

 instances of this are the life histories of beetles, butterflies, 

 and other insects in which the series of changes are most 

 pronounced ; other insects, on the contrary, leave the egg in a 

 condition which is not very dissimilar from that which they 

 ultimately acquire. Many crustaceans, molluscs and other 

 invertebrates are also liberated from the egg before acquiring 

 their definitive structure and outward form. Among the 

 Vertebrata the Amphibia constantly are hatched as " tadpoles," 

 which possess only the rudiments of limbs, and have gills like a 

 fish ; after a longer or shorter period under normal conditions, 

 the gills disappear, limbs grow out, and the adult frog or newt 

 is formed. Even among birds and mammals the young are 

 occasionally produced in a somewhat imperfect condition ; 

 though the differences between the newly-hatched bird and the 

 new-born mammal from their parents are not nearly so great 

 as in the case of the Amphibia. 



* Bc'tenc,", vol. ix., p. 3l>. f Zoologist, vol. ix.. p. 3022. 



