common to North Aynerica and Europe. 473 



Mr. Lvell endeavors to show that all our efforts to remove 

 a species from its type are successful only to acertain extent, 

 and that the maximum deviation is attainable in a iew gen- 

 erations.* The lamarckian contends that the lapse of time 

 and amount of physical revolution are not sufficient to cause 

 any appreciable difference between the embalmed Egyptian 

 remains and the forms now existing ; but we are at liberty to 

 step into the field of palaeontology, and here, at least, we 

 should be able to find proofs of a gradation of species, as I 

 believe Cuvier remarks. If this view is sustained by facts, it 

 becomes an important argument, and one which is generally 

 regarded as final ; but that it should not be received as abso- 

 lutely conclusive, I will endeavor to show. 



Let us, for a moment, suppose a transmutation of species 

 possible, and then attempt to account for the asserted absence 

 of the intermediate links. In the first place, the ability to 

 produce these links would constitute the main ground, (the 

 possibility of hybridity being commonly overlooked) for prov- 

 ing the identity of the two previously-admitted species — a 

 mode now in use, and considered of great service, especially 

 when it is well understood that there are distinct species, 

 among the Unionidae, for example, actually differing less from 

 each other than the known varieties of certain variable spe- 

 cies,! which a lamarckian might suppose to be of so recent 

 an origin as not to have yet become settled in the possession 

 of their proper diagnostic characters.t Indeed, notwithstand- 



due time. Some insects, which are usually apterous, acquire wings under certain 

 circumstances. Westwood's Introduction, ii. 468, 4S1. 



* Entertaining the opinion that the color of the native American depends upon 

 climate, it was not unusual for authors of the last century to affirm that the descend- 

 ants of Europeans had already made some progress in a change of color, Azara 

 states that the Russians are black. Marco Polo affirms that some of the distant 

 Orientals had tails. Dr. Prichard asserts that the heads of the white race in the 

 West Indies approach those of the original natives in form, independently, as he 

 seems to suppose, of intermixture ; and that the climate of Virginia, which was 

 formerly said to darken the European, nov,,- bleaches the skin, and converts the wool 

 of the blacks into hair in a few generations, when they are kept in the families of 

 their employers, whilst the field laborers retain the original color. 



t Mr. Lyell admits that, if this should be the case, it would have a tebdency to 

 cast an additional doubt upon the definite nature of species. 



X See my Freshwater Univ. Mollusca. Plakokbis, p. 26. 

 53 



