LAMARCK'S THEORY OF EVOLUTION 265 



supposition for this : I call to witness all observing 

 naturalists. 



" Not only many genera, but entire orders, and 

 some classes even, already present us with portions 

 almost complete of the state of things which I have 

 just indicated. 



" However, when in this case we have arranged the 

 species in series, and they are all well placed accord- 

 ing to theiF natural relations, if you select one of them, 

 and it results in making a leap {saut pardessui) over 

 to several others, you take anothej one of them a 

 little less remote ; these two species, placed in com- 

 parison, will then present the greatest differences 

 from each other. It is thus that we had begun to 

 regard most of the productions of nature which occur 

 at our door. Then the generic and specific distinc- 

 tions were very easy to establish. But now that our 

 collections are very much richer, if you follow the 

 series that I have cited above, from the species that 

 you first chose up to that which you took in the sec- 

 ond place, and which is very different from the first, 

 you have passed from shade to shade without having 

 remarked any differences worth noticing. 



" I ask what experienced zoologist or botanist is 

 there who has not thoroughly realized that which I 

 have just explained to you ? 



" Or how can one study, or how can one be able 

 to determine in a thorough way the species, among 

 the multitude of known polyps of all orders of radi- 

 ates, worms, and especially of insects, where the 

 simple genera of Papilio, Phalaena, Noctua, Tinea, 

 Musca, Ichneumon, Curculio, Capricorn, Scarabseus, 

 Cetonia, etc., etc., already contain so many closely 

 allied sjpecies which shade into each other, are almost 

 confounded one with another? What a host of 

 molluscan shells exist in every country and in all seas 

 which elude our means of distinction, and exhaust 

 our resources in this respect ! Ascend to the fishes, 



