MEDICINE IN MODEEN TIMES. 715 



Now the latter of these classes is exclusively, and the former all 

 but exclusively, aquatic. The more perfect, again, an insect's 

 metamorphosis, i. e. its power of building up tissues and organs, 

 the more perfect ordinarily, or rather the more profound, has been 

 its quiescence as a pupa. Indeed, the very exception here proves 

 the rule, and proves it to be a good one ; for such hemimetabolous 

 insects as, like May- and dragon-flies, come, in their imago state, to 

 differ almost as much from their larval forms as the imagos of 

 many holometabolous insects do from their larvae, are during those 

 preparatory stages as completely aquatic as any crustacean (West- 

 wood, ' Introduction to Entomology,' vol. ii. pp. 29, 38 ; Carus and 

 Gerstaecker, ' Handbuch der Zoologie,' p. 29). I am aware that 

 there is such authority as Mr. Paget's (' Surgical Pathology,' ed. 

 Turner, p. 123) and Mr. Darwin's ('Animals and Plants under 

 Domestication/ vol. ii. p. 15) in favour of regarding the power of 

 repairing injuries as standing in an inverse ratio to the amount of 

 metamorphotic change through which an animal has gone ; and I 

 must therefore take the more pains to show that my explanation, to 

 the effect that this happy power depends mainly upon the peace- 

 fulness and quiet with which the various processes of life ^re carried 

 on ordinarily, and after the mutilation, is the truer one. My 

 opponents' case would rest on such facts as these which follow. I 

 will give them first, and then show how they really support my 

 views. The larvae or tadpoles of the tailless Batrachia, but not 

 the adults, says Dr. Giinther (Darwin, loc. cit., and Owen, * Com- 

 parative Anatomy of the Vertebrate Animals,' vol. i. p. 567), are 

 capable of reproducing lost limbs. So with insects, says Mr. Dar- 

 win, 1. c, ' the larvae reproduce lost limbs, but, except in one order ' 

 (the Orthoptera, and amongst them the Phasmidae ^), ' the mature 

 insect has no such power.' There is, however, one common property 

 which lies at the bottom of the power of repair both in the larval 

 forms and in the perfect adult animal, both in the invertebrata and 

 in the vertebrata specified. This common property is the compara- 

 tive insignificance of the apparatus for aerial respiration: in all alike 

 — in the larva of the anurous amphibia, in the larva of the butterfly, 



* There seems to be some little doubt whether even a Phasma can regenerate lost 

 parts after its last moult, and some authorities i?srould not consider it adult till after 

 such ecdysis. The Crustacea, however, moult many times after attaining th^ adult 

 state, i. e. a state in which they can reproduce <Ae species. 



