MANUAL OF THE MOLLUSCA. 



this is a false as well as a degrading view of the matter. The 

 labours of the most eminent systematists have been directed to 

 the discovery of the subordinate value of the characters deriv- 

 able from every part of the animal organization ; and, as far as 

 their information enabled them, they have made their systems 

 expressive " of all the highest facts, or generalisations, in natui-al 

 history." (Oicen.) 



M. Milne Edwards has remarked, that the actual appearance 

 of the animal kingdom is not like a well-regulated army, but 

 like the starry heavens, over which constellations of various mag- 

 nitude are scattered, with here and there a solitary stai' which 

 cannot be included in any neighboming gTOup. 



This is exceedingly true ; we cannot expect our, systematic 

 groups to have equal numerical values,* but they ought to be of 

 equal structural importance ; and they will thus possess a sym- 

 metry of order, which is superior to mere numerical regularity. 



All the most philosophic naturalists have entertained a belief 

 that the development of animal forms has proceeded upon some 

 regular plan, and have directed their researches to the discovery 

 of that "reflection of the divine mind." Some have fancied 

 that they have discovered it in a mystic number, and have ac- 

 cordingly converted all the groups mio fives. ■\ We do not under- 

 value these speculations, yet we think it better to describe things 

 so far only as we know them. 



Great difficulty has always been found in placing groups 

 according to their affinities. This cannot be effected in — the 

 way in Avhich we are compelled to describe them — a single series ; 

 for each group is related to all the rest ; and if we extend the 

 representation of the affinities to very small groups, any arrange- 



* The numerical dev'elopment of groups is inversely proportional to the 

 bulk of the iiidiviciuals composing them. ( Waterhoicse.) 



t The quinarians make out five molluscous classes, by excluding the tuni- 

 cata ; the same end would be attained in a more satisfactory manner by re- 

 ducing the pteropods to the rank of an order, which mighi be placed next to 

 the opistho-hranchei. 



I 



