Mr. J. D. Dana on Species. 485 



shine, and often to artificial heat, is greater than a collector in a 

 temperate climate, and residing in weather-tight roomy houses, 

 can have any conception of. These remarks are merely my 

 apology for not collecting everythmg, which stay-at-homo natu- 

 ralists often imagine may be as easily done anywhere else as in 

 Encrland. 



XLVI. — Thoughts on Species. By James D. Dana *. 



While direct investigation of individual objects in nature is 

 the true method of ascertaining the laws and limits of species, 

 we have another source of suggestion and authority in the com- 

 prehensive principles that pervade the universe. The source of 

 doubt in this synthetic mode of reaching truth consists in our 

 imperfect appreciation of universal law. But science has already 

 searched deeply enough into the different departments of nature 

 to harmonize many of the thoughts that are coming in from her 

 wide limits ; and it is well, as we go on in research, to compare 

 the results of observations with these utterings of her universality. 



I propose to present some thoughts on species from the latter 

 point of view, reasoning from central principles to the circum- 

 ferential, and, if I mistake not, we shall find the light from this 

 direction sufficiently clear to illumine a subject which is yet in- 

 volved in doubts and difficulties. 



The questions before us at this time are — 



1. What is a species ? 



2. Are species permanent ? 



3. What is the basis of variations in species ? 



1 . JVhat is a species ? 



It is common to define a species as a group, comprising such 

 individuals as are alike in fundamental qualities; and then by 

 way of elucidation, to explain what is meant by fundamental 

 qualities. But the idea of a group is not essential ; and more- 

 over it tends to confuse the mind by bringing before it, in the 

 outset, the endless diversities in individuals, and suggesting 

 numberless questions that vary in answer for each kingdom, 

 class, or subordinate gi'oup. It is better to approach the subject 

 from a profounder point of view, search for the true idea of di- 

 stinction among species, and then proceed onward to a consi- 

 deration of the systems of variables. 



Let us look first to inorganic nature. From the study of the 

 inorganic world we learn that each element is represented by a 



* From Silliman's Journal for Nov. 18.5"; having been read before the 

 America!! Association at Montreal, Aug. 13, 185/. 



