284 ON THE CLASSES OF THE 



Same genera, nay, even in the same species, after a most 

 extraordinary manner. There was thus no good founda- 

 tion for believing that entomologists had done wrong in" 

 placing the Thysanura near to the Myriapoda, or that 

 Lamarck had erred in causing them to form one group. 

 But I began to suspect that the real character of this ap- 

 parently heterogeneous assemblage was to be discovered 

 less in the number of feet, which varied, than in some more 

 striking peculiarity which might be found common to both 

 the Thysanura and Myriapoda. The most obvious point 

 of similarity between them was that they were both true 

 insects, breathing by tracheal stigmata, and undergoing, 

 if any, at least a very imperfect metamorphosis. But 

 there were other Annulosa of this character as well as the 

 Myriapoda and Thysanura which proved either that such 

 a class, if instituted, was not yet rigorously denned, or 

 that if it was, many other and very dissimilar animals 

 must be assembled together in the same group. Such 

 conclusions could not do otherwise than discourage me, 

 as they showed symptoms of an artificial distribution, and 

 indicated my having thus touched on the very rock which it 

 had been all my endeavour to avoid. It added also not a 

 little to my being convinced that I had not yet arrived at 

 the secret of Nature, to observe that though some of the 

 Vermes approached much nearer in general appearance 

 to the genus Julus among the Myriapoda than did the 

 Parasita or Anoplura of Leach, yet that these last were 

 very nearly allied to the Thysanura. 



I had almost despaired of success in my attempts to ar- 

 range these various groups, which, though so dissimilar, 

 have an universally acknowledged affinity, and had even 

 commenced a review of my opinions as to there being no 



