Translated by Philip H. Nicklin. 107 



sion in its pages. The important question, ^' v;hat is species ?^^ 

 which he asks but does not answer, seems to present itself at the 

 beginning of every arrangement ; and that naturalist would be 

 canonized who should answer it in a manner acceptable to all. 



The definition given by Milne Edwards in his Elemens de 

 Zoologie, seems to be sufficient for the purpose of arrangement : 

 " On donne le nom d'espece a la reunion des iiidividus qui se re- 

 produisent entre eux avec les memes proprietes essentielles." 



P. H. N. 



Philadelphia, April 10, 1841. 



Gen&xd Considerations on the Reform which ought to take place 

 in restricting the number of Species of the genera Unio and 

 Anodonta. Presented to the Linnaean Society of Bordeaux, at 

 its sitting of the 5th of July, 1839, on the occasion of the pub- 

 lication of Mr. Isaac liCa's second volume of Conchological 

 Observations. By Ch. Des Moulins, Member of the Linnasan 

 Society of Bordeaux, &c. 



Gentlemen — An able designer had arranged, in a hundred ad- 

 joining compartments, a hundred figures, of which each one dif- 

 fered so little in appearance from its neighbor, as to be indistin- 

 guishable at the first glance. The first was the figure of the 

 Apollo Belvidere, the last was that of a frog. This curious com- 

 parison shadows forth a relation little flattering to the physical 

 man, but of much importance in a philosophical* point of view, 

 in the sense now attached to this word. It is the graphic repre- 

 sentation of the celebrated maxim of Linnaeus, Natura nonfadt 

 saltum — ' Nature makes no leaps.' 



But really, gentlemen, what is nature? Nature, according to 

 the notion of Linnseus, in the opinion of Christians, in truth is 

 nothing else than the whole of those laivs, or material order, which 

 God imposed on physical things when he created them. Now 

 gentlemen, this saying of Linnaeus is admirable, it is profound, it 

 is true in the material order, the object at once of the study and 

 teaching of the Professor of Upsal ; and the more worthy it is of 

 our respect, the greater is the necessity of adding to it a commen- 

 tary, restraining its scope within the bounds contemplated by its 

 immortal author. 



* The use of this word often appears to me grammatically absurd ; sometimes, 

 instead of it, we ought to say physiological, but oflener metaphysical ; but unfor- 

 tunately the latter frightens children, even children of all ages. 



