Phylogeny and Evolution of the Lepidoptera. 577 



I feel satisfied that the flat egg in the Macro-hctrrocera 

 has also two (at least) different forms, the difficulty of 

 defining them does not deter me from this condusion, 

 since the greater difficulty in the case of the upright egg 

 is, nevertheless, merely a difficulty, and not a reason for 

 refusing to accept two forms of upright egg. 



The two forms oi fiat egg are the Geometrid and the 

 Bombycid. The former is marked by greater rough- 

 ness, the lines or ribs forming the network or 

 sculpturing, are larger and coarser, the Bombycid egg is 

 smoother and more polished, yet many instances could 

 be quoted in fiat contradiction to this distinction. The 

 tendency of the Geometrid egg is to have a denser harder 

 shell than the Bombycid, though here, again, many of the 

 larger Bombycids have very firm eggshells. 



AVhether this division between Geometrid and Bombycid 

 eggs will hold good, it remains true that both divisions 

 are, in their typical forms, very distinct from the upright 

 egg, and whilst I am, for reasons that may or may not be 

 sound, inclined to derive the two forms of flat egg from 

 distinct origins very low down in the evolutionary scale, 

 it appears probable that the two forms of upright eggs, 

 moths and butterflies, had a common origin, though very 

 low down, and have long baen separate. 



In placing together all the families (of Macros) that 

 have uprighi; eggs, and looking for some other character 

 they may have in common that will confirm such a collo- 

 cation, we find a most valuable one in the chin glands of 

 the larvfe. This curious structure is of so special a 

 nature, that it would require very strong evidence to 

 make one believe that it was separately acquired in 

 different families, and so when we find that it occurs 

 in butterflies, in Noctufe, and in Notodonts, but 

 nowhere amongst the families with flat eggs, the 

 conclusions derived from the egg seem very strongly 

 confirmed. 



No one can doubt that the butterflies are widely 

 separated from the Noctua?, and the evidence of the 

 Hesperid pupa shows that the butterfly separated from 

 the Noctua stirps a very considerable way below any 

 Noctua-like form, usually placed with the Macros. But 

 this evidence of egg and larval chin gland suffices to 

 show that they jointly separated from the Geometrid and 

 Bombycids still lower down. 



