394 ON THE ORDERS 



We may add that an analogy of form and manners is visi- 

 ble also bet^veen the Phalaiigidea and the larvas of He- 

 miptera, between the Acari and the parasitical larvse of 

 the corresponding group of Ilaustellata. 



But granting that the analogical relations between these 

 two classes are not so visible as those which exist between 

 the Arachnida and Crustacea, (although the above exam- 

 ples, in my opinion, amount to a perfect demonstration of 

 their having a real existence,) it is to be observed, that rela- 

 tions of analogy are sometimes disguised in such a manner 

 that they are only to be remarked by the ordinary observer 

 when pointed out to his notice. In the eyes of any person 

 at first sight, few groups can be more dissimilar than the 

 Ametahola and Mandibulala; yet they are contiguous, and 

 therefore ought, according to what has been said, to have 

 relations of analogy between their corresponding types. 

 Now, if such can be pointed out as existing under a dis- 

 guise, and as being particularly curious when unmasked, 

 it is perhaps a fair inference to suppose that two contigu- 

 ous circles, like those of Haustellata and Arachnida, 

 which differ as much or even more than the former two 

 in general structure, may likewise have these analogies 

 depending upon some secret of Nature. It is obvious 

 that the analogies will thus be rendered less liable to de- 

 tection than those which depend on the external appear- 

 ance simply. Another argument in favour of this con- 

 jecture is, that in both cases we are leaving insects which 

 undergo a perfect metamorphosis for those which are sub- 

 ject to an imperfect one, or which only shed their external 

 envelope. But we must leave inferences for facts; and, 

 in the first place, have to explain why the above-men- 

 tioned analogies of external appearance, between the cor- 

 responding groups oi Arachnida and Haustellata, are not 



