56 



of the individual. It is difficult to see how evolution could 

 have arisen in the egg stage, but the different forms of the 

 lepidopterous ovum show that it has taken place. The shell 

 of the ovum, when once formed within the body of the female, 

 cannot then alter its structure, and therefore, when once the 

 ovum is deposited, no further evolution in structure can take 

 place in that particular ovum, though we know that the 

 ovum, even after deposition, does in some cases suffer 

 a change in the colour of the shell, as in the ova of the 

 genus Hepiahts. The apparent evolution of the ovum in its 

 external appearance is really, therefore, imaginal evolution, 

 affecting those organs of the female imago which form the 

 shell of the egg. 



Those species which comprise the genus Coleophora have, 

 in the imaginal condition, so many essential features in 

 common that they are still, even in these days when the 

 splitting up of genera is so much in vogue, all included in 

 the same genus. We have in Britain alone some eighty 

 species, and thanks chiefly to the efforts of Mr. Henry 

 J. Turner, we now know the ova of a bare dozen species. 

 Among these few ova that we do know there are three 

 distinct types. Coleophora ccBspitiiiella has an ovoid egg 

 without any sculpture. Then we find the ribbed ovum of 

 C . fuscedinella and its allies, from which the larva emerges 

 into the atmosphere before commencing its mine in the leaf 

 of its food-plant. Thirdly, there is the very evident upright 

 egg with a flat base of C. gryphipennella and others, through 

 the base of which the larva bores direct into the leaf without 

 coming into the outer atmosphere at all. Yet the oval life 

 in all these is much the same ; they all hatch in a few days ; 

 none of them hibernate in the ovum. It appears, therefore, 

 that though the Coleophorids, judging from their imaginal 

 characters, have all reached to such a point in their develop- 

 ment that entomologists place them all in the same genus, 

 which shows, at least, that they have all a very similar 

 appearance — neuration, etc, — yet in their oval life some 

 species have progressed further than others, or, in any case, 

 have developed in three separate directions, giving rise to 

 three separate types of ovum. Again, these two species of 

 the genus Dicranura, erminca and vinula, are very closely 

 allied in the larval and imaginal stages, and yet the shape of 

 the ovum is different in each species. Speaking generally 

 of the ovum, we find that ova laid by the same individual 

 vary m size and in proportion of height to breadth, and, in 

 the ribbed forms, also in the number of ribs. It is well 



