222 THE ORIGIN AND DEVELOPMENT 



extends to the front margin of the wing, because 

 the subcostal area reaches that margin. On the 

 hind wings of these butterflies almost the only 

 element for the formation of an ocellus is a short 

 bar in the same area resembling one on the front 

 wings ; yet from this a complex ocellus, not so 

 imposing as that of the front wings certainly, but 

 still a marked ocellus, has been formed ; which, 

 true to law, just fails of reaching the front mar- 

 gin, keeping within the normally narrower limits 

 of the subcostal area of the hind wing. 



This distribution of the veins enables us also to 

 point out an interesting relation between the orna- 

 mentation of the front and hinder portion of a 

 single wing, which seems never to have been 

 noticed, and which shows again both the strength 

 and the weakness of symmetry. The relation of the 

 ornamentation of the hind to the fore wing is not 

 one of slavish repetition ; indeed our ingenuity 

 may often be taxed to discover it. But the rela- 

 tion of the two parts of the same wing has even 

 less of repetition ; for to a certain extent there is 

 a polar distribution of markings. For instance, 

 there is often a bright-colored ocellus at the inner 

 angle of the hind wing, in the area of the fourth 

 principal vein ; should a single similar ocellus, or 

 a bright-colored spot corresponding to it, occur in 

 any other part of the wing, there is only one 

 place where it will fall, viz., at an exactly cor- 



