266 report— 1856. 



Prof. Adams had before collected about the same number of marine species 

 at Jamaica ; and, holding the theory that no species could be common to the 

 two oceans, he was well qualified to detect any sources of error which might 

 have militated against his own hypothesis. The very minute discrimination 

 also to which he had accustomed himself in his researches among the land 

 shells of Jamaica, would at once prevent him from confounding similar 

 species. And as he visited no other spot than the shores of Panama, and 

 the neighbouring island of Taboga, there is no danger of the admixture of 

 specimens from different localities. The results of the expedition were " read 

 before the Lyceum of Natural History, May 10th, 1852," and published in 

 their Annals, vol. v. They also appear under a separate form as a " Cata- 

 logue of Shells collected at Panama, with Notes on their Synonymy, Station, 

 and Geographical Distribution, by C. B. Adams, Professor of Zoology, &c. 

 New York, 1852, pp. 334, Svo." The author gives all his references from 

 personal research : quotes every assigned habitat, with authorities (discri- 

 minating original testimony by the mark !) ; and, in addition to his own 

 remarks, states the number of specimens from which he writes. He was not 

 able to dredge, nor to make observations on the animals : but for the shore 

 shells, including the minute species, there is scarcely anything left to be 

 desired. The author describes 157 as new species: of the value of many of 

 these there will be two opinions. Prof. Adams in his work on Jamaica shells, 

 "Contributions to Conchology,'' pp. 84 et seq., gives up the common opinion 

 that species are natural groups, while genera, &c. are artificial : and as he 

 believes that there are different species as well as varieties of mankind, it is 

 natural that he should distinguish as species of shells what others might con- 

 sider varieties, and as varieties what may be accidents of growth. To the 

 discerning reader, however, this does not interfere with the extreme value of 

 the work. In a branch of inquiry so overburdened with carelessly observed 

 or recorded facts, the freedom from the usual sources of error is a matter of 

 the first importance. Where a species has originated in a mere theory, as 

 in the case of common types from the two oceans, the student is at once on 

 his guard. Where it arises from deficiency of materials, as in the Cczca t 

 additional knowledge will soon set the error right. And in the present state 

 of our ignorance, to designate forms as species which will hereafter have to 

 be united, is much more pardonable than to overlook differences, all of which 

 should be carefully noted before we can obtain a Natural history of any 

 single species*. There appear to be three stages in our progress towards 

 truth. In the first, objects are united, simply because their differences are 

 not appreciated : as when Dione lupinaria was considered a variety of Venus 

 dione, Linn., simply because they were each spiny. In the second, minute 

 differences are appreciated, while their harmonies are overlooked. Such is 

 the present ordinary condition of conchological science, as represented in 

 the Achatinellce, Cylindrellce, Anomiada?, &c. In the third, species are re- 

 united, with a full perception of the differences among them, from a greater 

 knowledge of the range of variation of which living creatures are susceptible. 

 This third stage, when faithfully performed on sufficient evidence, should not 

 be spoken of as " confounding species," and is one of the greatest pieces of 



* In the " Researches on the Foraminifera," Trans. Roy. Soc. 1855, p. 228, Dr. W. B. Car- 

 penter states, that "multitudes of species" will be shown in the present Report to "have been 

 instituted in various genera of Californian shells by the late Mr. C. B. Adams, whose identity 

 is established by a more extended comparison of individuals." This sentence appears simply 

 to embody the impression left by conversation, and not to do justice to the Professor. As I 

 am answerable for the impression I made, I have to request that those who possess the 

 Transactions will make the following corrections : — For " multitudes of species" read " several 

 species," and for "Californian shells" read "shells of Jamaica and Panama." 



