HELOTIN^ AND CH^TODONfD^. 



25 



connecting the Holocentrincs with the PercidcB — would 

 bring us back again to the last; or, in other words, would 

 complete the circle which the above remarks of Cuvier 

 place beyond doubt. Nature, indeed, will ever laugh, 

 as it were, at our attempts to circumscribe her groups 

 by absolute characters of our own invention ; but she 

 almost invariably points out her own course, if we are 

 sufficiently humble and unprejudiced to follow it. 



The external analogies of the 

 Helotince are no less interest- 

 ing than their affinities : they 

 obviously represent the Spa- 

 r rid<B in this family, and give us 



also a beautiful representation 

 of Gerris Plumieini (^fig. 2.) 

 and its allies j so close, in^ 

 deed, in external form, that 

 the similitude cannot possibly 

 be greater : this will be at once 

 apparent from the outlines 

 here given of the heads of the 

 genera Datnia (a), and Gerris 

 (6). Having now closed the 

 circle of the Percidae, we proceed to the next, or sub- 

 typical family. 



(22.) The Ch^todonid.i:, or chsetodons, are not 

 only the most beautiful of the spine-backed order, but 

 of the whole class of fishes. With the exception of the 

 green and richly coloured Labrince, nearly the whole, 

 and certairJy all the typical groups, are confined to the 

 warm latitudes of the tropics, and the shores and islands 

 washed by the great Pacific Ocean. None of them are 

 large fishes, while all appear to be nutritious and savoury 

 food. The family is more numerous even than that of 

 the perches, and contains such an immense assembly of 

 greatly diversified groups, that only a few characters are 

 applicable to the whole. From the perches, however^ 

 they are chiefly distinguished by the pre-operculum not 



c 4 



