v.] METAMORPHOSES OF INSECTS. 93 



the water-inhabiting and water-breathing- Crustacea 

 must be regarded as the original stem from which 

 the other terrestrial classes, with their tracheal respi- 

 ration, have branched off." Haeckel, 1 moreover, is of 

 the opinion that the Tracheata are developed from 

 the Crustacea, and probably from the Zoepoda. 

 For my own part, though I feel very great diffidence 

 in expressing an opinion at variance with that of 

 such high authorities, I am rather disposed to suggest 

 that the Campodea type may possibly have been 

 derived from a less highly developed one, resembling 

 the modern Tardigrade, a (Fig. 56) smaller and much 



FIG. 56, Tardigrade (after Dujardin). 



less highly organized being than Campodea, which 

 has been successively placed among the Acari and 

 the Rotatoria. It possesses two eyes, three anterior 

 pairs of legs, and one at the posterior end of the 

 body, giving it a curious resemblance to some Lepi- 

 dopterous larvae. 



These legs, however, as will be seen, are reduced 

 to mere projections. But for them, the Tardigrada 

 would closely resemble the vermiform larva so com- 

 mon among insects. Among the Coleoptera, for in- 

 stance, this type occurs in the weevils ; among Hy- 



1 Jedenfalls haben sich die Tracheaten aus den Crustaceen, und 

 hochst wahrscheinlich aus den Zoepoden entwickelt. Allgemeine 

 Bntwickelungsgeschichte der Organismen, p. xciii. See also p. xc/iii. 



