ix] PAST AND PRESENT 109 



are on the whole less specialised in structure than 

 those which pass through a complete transformation. 

 These two considerations, taken together, suggest 

 strongly that in the evolution of the insect class, 

 the simpler life-history preceded the more complex. 

 Such a conclusion seems reasonable and what might 

 have been expected, but we are confronted with the 

 difficulty that if the most highly organised insects 

 pass through the most profound transformations, 

 then insects present a remarkable and puzzling ex- 

 ception to the general rules of development among 

 animals, as has already been pointed out in the first 

 chapter of this volume (p. 7). A few students of 

 insect transformation have indeed supposed that the 

 crawling caterpillar or maggot must be regarded as 

 a larval stage which recalls the worm-like nature of 

 the supposed far-off ancestors of insects generally. 

 Even in Poulton's classical memoir (1891, p. 190), 

 this view finds some support, and it may be hard 

 to give up the seductive idea that the worm-like 

 insect-larva has some phylogenetic meaning. But the 

 weight of evidence, when we take a comprehensive 

 survey of the life-story of insects, must be pro- 

 nounced to be strongly in favour of the view put 

 forward by Brauer (1869), and since supported by 

 the great majority of naturalists who have discussed 

 the subject, that the caterpillar or the maggot is 

 itself a specialised product of the evolutionary 



