NESTLING BIRDS AND WHAT THEY TEACH 253 



almost equal certainty, represent comparatively recent develop- 

 ments. 



Thus the spots in the young lion and the faint traces thereof 

 in the adult female are almost certainly remnants of an earlier 

 and more emphatically spotted phase common to the adults of 

 both sexes. But it is also possible that in many cases these 

 markings may be remnants of an earlier spotted immature 

 stage when the young derived, and may still derive, benefit from 

 the protection accruing from these markings. In such cases the 

 adults may have been quite differently coloured as they com- 

 monly now are. 



According to the prevailing opinion, we have something 

 like a recapitulation of past types of coloration, the markings 

 of ancestral adult stages being reproduced in the immature 

 stages of to-day. On this assumption we must suppose either 

 that this immature coloration is now merely reminiscent and 

 of no protective value, or that the descendants of these spotted 

 or striped forms, as the case may be, require the ancestral adult 

 protective colours only during the period of immaturity. 



But even this view cannot be reconciled with Elmer's inter- 

 pretation of the significance of these markings. If longitudinal 

 stripes are the result of adaptations to foliage of monocoty- 

 ledonous plants, and spot marking to an adaptation to foliage 

 of vegetation which cast spotted shadows, then the longitudinal 

 markings of many animals of to-day must be quite out of 

 harmony with their environment, and their survival shows that 

 in these cases at least the correspondence between the markings 

 and the type of foliage need not be-a very close one, since the 

 longitudinal stripes developed to harmonise with linear foliage 

 serves equally well amid foliage which casts spotted shadows. 



Transverse stripes, at least, apparently owe their origin to 

 adaptation to totally different environments. Originally de- 

 veloped for the sake of affording protection amid linear foliage, 

 as in the tiger, for instance, they have almost certainly been 

 acquired de novo in the case of the zebra, where they serve to 

 protect the animal on account of the absence of foliage of any 

 sort. 



The contention that longitudinal striping was developed in 

 I'esponse to linear foliage is lacking in cogency. Vertical stripes 

 would have served the purpose better, supposing that the 



