204 COLOUR IN NATURE chap. 



associated with a sculpturing of the shell. Accord- 

 ing to the Countess Maria von Linden, both the 

 sculpturing and the colours show a definite orderly 

 progression in which phylogeny and ontogeny run 

 parallel. In the garden snails, Helix nemoralis and 

 H. hortensis, there is an extraordinary amount of varia- 

 tion in the bands, but nothing is known of the reason. 

 Vertebrates. — So far we have seen that colour- 

 patterns are best developed in animals in which 

 there is a distinct segmentation of the body, that in 

 unspecialised forms they show a direct relation to 

 the segments, but that as specialisation proceeds, 

 they tend to lose this simple and direct relation. 

 When we pass upwards to Vertebrates, we find that 

 an apparent relation to segmentation is completely 

 lost. It is true that in the case of the ringed snake, 

 as we shall see, there appears to be a direct relation 

 between the ornamentation and the arrangement of 

 the cutaneous blood-vessels, and these may well have 

 a segmental significance, but at the same time the 

 statement on the whole is true that a direct relation 

 between the markings and the segmentation of the 

 Vertebrate body is no longer obvious. In the general 

 case the pattern in a Vertebrate dominates the whole 

 organism and is not produced by the repetition of 

 one colour scheme. This is perhaps an advance due 

 to the perfect synthesis of the body, just as the 

 frequent striking difference between the fore and 

 hind wings of a butterfly is an advance when com- 

 pared with the segmental patterns of caterpillars ; 

 or it may be an indication that the segmentation of 

 a Vertebrate is in essence a different thing from that 

 of a worm or an insect. 



