as a Branch of Natural History^ 6^c. " 88ft 



to other genera and orders, but it is of too general and too vague 

 a nature not to require some more precise indications for each, 

 particular sort of division. 



§ 48. Accordingly we find, that those animals or plants have 

 been considered as belonging to the same species, which have been 

 found on comparison to be so like each other, as, to use Haiiy's 

 expressions, to be distinguished only by separate existence, or 

 in which each individual may be supposed to represent the 

 whole species, provided, however, due allowance is made for the 

 differences arising from the sex and the age of the animal, and 

 the season of the year in which it happens to be living ; so that 

 individuals should be compared only with individuals of the 

 same sex, of the same age, and living at the same epoch. But 

 even such a definition, though much more accurate and precise 

 than the preceding, would still be thought deficient in complete- 

 ness and accuracy ; if the expression of a general law of nature, 

 including as a consequence all that has just been alluded to, 

 had not been found to answer all the purposes of the most phi- 

 losophical naturalist. This law is that of reproduction, by which 

 individual beings are incessantly generated, perfectly similar to 

 the parents from which they originate : so that the individuals 

 belonging to the same animal or vegetable species^ are supposed 

 to be descended from parents similar to them, and differing from 

 all others. In this case, and when a clearly and precisely ex- 

 pressible law is made to comprehend all the individual beings 

 which are members of the same species, the differences existing 

 among them, which cannot be accounted for by any expressible 

 law, and which, by their small importance, and our ignorance of 

 their causes, may be looked upon as accidental, will be ranked only 

 as characterizing mere varieties, either constant or accidental. 



§ 49. Now, by the very nature of the beings belonging to the 

 mineral kingdom, no such thing as reproduction exists in mine- 

 rals, so that this particular law cannot afford us any aid ; but 

 the more general fact of individuals being supposed to belong 

 to the same species, as soon as they may be brought together 

 under the expression of some definite law, will easily find its ap- 

 plication as well in the unorganized as in the organized world. 

 In this way crystals agi'eeing together, as well in chemical com- 

 position as in their form, not, however, primary or fundamental 

 form, but in their actual form, be it secondary or analogous to 



