INTRODUCTION. 



19 



Differences of this kind, between organized beings, are what are termed varieties. 



There is no proof tliat all the differences which now distinguish organized beings are 

 such as may have been produced by circumstances. All that has been advanced upon 

 this subject is hypothetical : experience seems to show, on the contrary, that, in 

 the actual state of things, varieties are confined within rather narrow limits ; and, 

 so far as we can retrace antiquity, we perceive that these limits were the same as at 

 present. 



We are then obliged to admit of certain forms, which, since the origin of things, 

 have been perpetuated without exceeding these limits ; and all the beings appertaining 

 to one of these forms constitute what is termed a species. Varieties are accidental 

 subdivisions of species. 



Generation being the only means of ascertaining the limits to which varieties may 

 extend, species should be defined the reunion of individuals descended one from the 

 other, or from common parents, or from such as resemble them as closely as they 

 resemble each other ; but, although this definition is rigorous, it will be seen that its 

 application to j^articular individuals may be very difficult when the necessary experi- 

 ments have not been made.* 



To recapitulate, — absoqDtiou, assimilation, exhalation, developement, and generation, 

 are the functions common to all living beings ; birth and death, the universal limits of 

 their existence ; a porous, contractile tissue, containing within its laminae liquids or 

 gases in motion, the general essence of their structure ; substances almost all 

 susceptible of being converted into liquids or gases, and combinations capable of easy 

 transformation into one another, the basis of their chemical composition. Fixed 

 forms, and which are perpetuated by generation, distinguish their species, determine 

 the complication of the secondary functions proper to each of them, and assign to them 

 the office they have to fulfil in the grand scheme of the universe. These forms 

 neither produce nor change themselves ; the life supposes their existence ; it can exist 

 only in organizations already prepared ; and the most profound meditations, assisted 

 by the most delicate observations, can penetrate no further than the mystery of the 

 pre-existence of germs. 



DIVISION OF ORGANIZED BEINGS INTO ANIMALS AND VEGETABLES. 



Living or organized beings have been subdivided, from the earliest times, into ani- 

 mate beings, or those possessing sense and motion, and inanimate beings, which enjoy 



* That insurmountable difficulties oppose the rigid determination of 

 species, and, consequently, render even the definition of the term 

 impossible, except in a very vague and loose manner, will readily 

 appear on consideration of some of the phenomena presented. 

 The pre^'alent idea is, that a species consists of the aggregate of 

 individuals descended from one original parentage, which alone are 

 sujiposcd to be capable of producing offspring that are prolific mter 

 !!■; and that when individuals, not of the same pristine derivation, 

 interbreed, the hybrids are necessarily mules, which are either quite 

 sterile, or at most can only propagate with individuals ot unmixed 

 descent. But it so happens, that every possible grade of ai)pro.\i- 

 mation is manifested, from the most diverse races, to those which are 

 utterly unnistinguishable ; while, even in the latter case, urgent ana- 

 logies, notwithstanding, sometimes forcibly indicate a separateness of 

 origin ; as when a series of analogous races inhabiting distant regions 

 are compared together, some of which are obviously different, others 

 doubtfully so, and some apparently identical. And it remains to be 

 shown whether such intimately allied races as some of these, even if 

 not descended from a common stock, (which of course cannot be 



ascertained), would not produce hybrids capable of transmitting and 

 perpetuating the mingled breed. It is true that Cuvier guards 

 against this contingency, in the wording of his definition ; and that 

 most naturalists would concur in regarding such misciblc races, how- 

 eA-er dissimilar, as varieties merely of the same ; but a question 

 arises, whether there be not di/?eren^ rfr^cci of fertility in hybrids, 

 corresponding to the amount of affinity, or physiological accordancy, 

 subsisting betwixt the parent races ; it being only within a certain 

 sphere of that atFinity that they can he produced at all ; besides which, 

 as hybrids are seldom exactly intermediate, and in some instances 

 (particularly among multiparous races) have been known to resemble 

 entirely one or the other parent, it may be presumed that this eireuni- 

 stanec would also materially affect their capability of propagation. 

 Experiments are needed to solve this important problem, though there 

 is every reason to suspect that the following proposition will eventu- 

 ally gain the general assent of naturalists, viz., that while consideratile 

 ttissimilarity does not of necessity imply specijical diversity, the con- 

 verse equnlly holds, that abnohtte resemblance fails of itself to cuu 

 ^titute specificat identity. — Ku. 



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