6 THE POPULAR SCIENCE MONTHLY. 



the generic lists of to-day ! In an article on the " Proteus of Lake 

 Erie," he expressed his aversion to multiplying names in zoology, 

 and lamented the tendency. He protested as follows, fifty years ago : 

 " By some, these innovations have been so wantonly introduced, as 

 almost to threaten in the end the erection of every species into a dis- 

 tinct genus." l Though these words were undoubtedly aimed at Rafi- 

 nesque, they were none the less prophetic. Whatever may be said 

 of the existence in nature, of other groups, there can be no question 

 that species have the most definite existence, and it would seem then 

 that nothing more need be proved for the theory of descent as 

 opposed to the theory of special creation, than the establishment of 

 the fact that species assume the characters of new species, or disap- 

 pear altogether with a change of surroundings. As examples might 

 be cited, the transplanting of Alpine seeds to warmer regions below, 

 and an accompanying change of the plant into another species before 

 known in the warmer region, or, more remarkable still, the change 

 of a species of Crustacean which lives in salt water, to another species 

 with a partial freshening of the water, and this freshening slowly 

 persisted in, the form changing into another genus, and in so doing 

 losing: one of its segments. In the first case we see the effect ol 

 temperature, and in the second case the physical influence of salt anfl 

 water in different proportions. 



Now, these and hundreds of similar examples can be incontestably 

 proved. 



Even the prolonged existence of the form of some animals, like 

 Lingula, may be referred to an inherent vitality which enables them 

 to survive changes that caused the death of thousands of others. 



In an early discussion of Darwin's theory, 2 Prof. Agassiz cited the 

 persistence of Lingula as fatal to the theory, and Prof. William B. 

 Pogers replied that the vital characters of some animals would enable 

 them to survive above others. Ten years later, I had an opportunity 

 of studying living Lingula on the coast of North Carolina, and 

 brought specimens home alive in a small jar of water, and kept them 

 in a common bowl for six months without the slightest care. Their 

 power of surviving under changed conditions their vitality, in other 

 words seems incredible. 3 (For further details, see reference below.) 



It has for a long time been suspected that the species of Jfollusca, 

 described in such profusion in this country, would be redubed when 

 the slightest attention to their habits had been made. Dr. James 

 Lewis 4 long ago observed that a certain species of fresh-water mussel, 

 described as Alasmodonta truncata, is only the truncate form of 

 another species, A. marginata. From a careful study of the condi- 



1 American Journal of Science and Arts, vol. vii., 1829. 



s " Proceedings of the Boston Society of Natural History," vol. vii., p. 231, December 

 15, I860. 



3 Ibid., vol. xv., p. 315. 4 Ibid., vol. v., p. 121. 



