CLASSIilGATION. 35 



The points wliicli we have principally to consider in 

 relation to the classification and position of the Tiiysa- 

 NUEA and CoLLEMBOLA are — the absence of metamor- 

 phoses ; the absence of wings ; the presence or absence 

 of trachese ; the structure of the mouth ; the saltatory 

 appendage ; and the ventral tube. 



The last-mentioned organ, though observed by most 

 of the preceding writers, has not, I think, attracted the 

 attention it deserves. It is, in fact, the true charac- 

 teristic of the group. The absence of wings and of 

 metamorphoses is not peculiar to the Collembola; in 

 fact the presence of metamorphoses is closely connected 

 with that of wings. To the trachege we must not 

 attach too much importance ; for though absent in the 

 great majority of the group, they occur in Smijnthurus. 

 The peculiar mouth-parts of the mandibulate genera are 

 entirely absent in Amira ; and the caudal appendage is 

 wanting in the Lipuridce. 



Thus, then, the ventral tube is characteristic as 

 being general to the species belonging to the Linncean 

 genus Poclura, and still more so, as being peculiar to 

 them ; at least, I know of no similar organ in any other 

 group of Articulata. The presence of tracheae, the 

 structure of the mouth, and the saltatory appendage, 

 all indicate a wide distinction between the Lepismidw 

 and the Podurw, and, when considered in conjunction 

 with the fact that the ventral tube is absent among the 

 former, force us to the conclusion that the two groups 

 are much less closely allied than has hitherto been 

 supposed. 



This was, indeed, fully recogijised by M. Gervais,^ 

 whose remarks on the subject I have already quoted 

 (ante, p. 32). Mr. Templeton has also expressed the 

 same opinion. He observes that^ " the Lepismidce should 

 be separated most markedly from the other division of 

 the Thtsanuea with which they are usually associated ; 

 the antennge, caudal apparatus, and more esj)ecially the 



1 ' Loc. cit., vol. iii, p. 378. 



" ' Trans. Ent. Soc. London,' 1842, p. 305. 



