1896. THE MEANING OF METAMORPHOSIS. 403 



specialised trough-like ambulacral furrows among the former, or in 

 special pouches, or in the gills of the latter. 



Professor Miall's view as to the causes of degeneration of insect 

 larvae approaches very close to that taken by the authors of this paper 

 some years since, but differs in that he assumes natural selection to 

 have been one of the active factors. It seems to us that the corre- 

 lations between the kind of food and the structures of the larvae, 

 whether degenerate or not, are obvious ; and the fact that the food 

 was directly supplied by the parent, or merely indirectly furnished by 

 the location of the ova, is not in our opinion anything more than the 

 expression of a habit which was not in any sense dependent upon 

 the possession of wings nor yet upon the necessity of distributing 

 the species in search of favourable fields. Some Coleoptera have 

 active larvae, as in Gyrinidae, although the parents are themselves 

 among the most restless of insects, and there are many examples of 

 wingless females, incapable of any extended travel, which lay their 

 eggs upon food-plants from which the larvae never stir until the plant 

 is destroyed. The example of the active larvae of Epicauta and Meloe 

 which forage for themselves, as do many parasitic larvae, and hunt 

 food and provide for their own development through several variable 

 stages and metamorphoses, as well as the great activity and migratory 

 capacity of the army-worm, among the larvae of Lepidoptera, are 

 not favourable to the view that there is any causative connection 

 between the activity of the parent and the capacity for active life of 

 the larvae. They are, however, favourable to the hypothesis that 

 traces obvious connection between the structures and habits of the 

 larvae and their surroundings. 



The structural modifications of the larvae are, so far as we can 

 see, the direct products of their habits and surroundings, and that 

 the former should be suitable, and therefore advantageous, is a 

 necessary and inevitable result. This result, in our way of looking 

 at the facts, seems to differ from ..the results of other physical causes 

 acting upon inorganic bodies, only in being obscured by the com- 

 plexity of organic structures and false mental habits of regarding 

 them. 



In other words, it is putting the cart before the horse to place 

 advantage as a cause when it is, together with the struggle for 

 existence (as first clearly stated by an eminent entomologist. 

 Dr. A. S. Packard), the result of the evolution of organisms which 

 has been directed and governed by other and more fundamental laws. 

 Boston, U.S.A. ' Alpheus Hyatt. 



J. M. Arms. 



