92 ESSAY ON CLASSIFICATION. Part I. 



Avriters have attempted to identify tliese two processes. In metamorphosis, as 

 observed among Insects, the individual born from an egg goes on undergoing change 

 after change, in direct and immediate succession, until it has reached its final trans- 

 formation ; but however different it may be at different periods of its life, it is 

 always one and the same individual. In alternate generations, the individual born 

 from an egg never assumes through a succession of transformations the character of 

 its parent, but produces, either by internal or external budding or by division, a 

 number, sometimes even a large number of new individuals, and it is this progeny 

 of the individuals born from eggs, which grows to assume again the characters of 

 the egg-laying individuals. 



There is really an essential difference between the sexual reproduction of most 

 animals, and the multii)lication of individuals in other ways. In ordinary sexual 

 reproduction, every new individual arises from an egg, and by a regular succession 

 of changes assumes the character of its parents. Now, though all species of animals 

 reproduce their kind by eggs, and though in each there is at least a certain number 

 of individuals, if not all, Avluch have sprung from eggs, tliis mode of reproduction is 

 not the only one observed among animals. We have already seen how new individ- 

 uals may originate from buds, which in their turn may produce sexual individuals ; 

 we have also seen how, by division, individuals may also produce other individuals 

 differing from themselves quite as much as the sexual buds, alluded to above, may 

 differ from the individuals which produce them. There are yet, still other com- 

 binations in the animal kingdom. In Polyps, for instance, every bud, Avhether it 

 is freed from the parent stock or not, gi'ows at once up to be a new sexual 

 individual ; while in many animals which multiply by division, every new individual 

 thus produced assumes at once the characters of those Ijorn from eggs.^ There 

 is, finally, one mode of reproduction which is peculiar to certain Insects, in which 

 several generations of fertile females follow one another, before males appear again.^ 



What comprehensive views the phj'sical agents must be capable of taking, and 

 what a power of comliination they must possess, to be able to ingraft all these 

 complicated modes of reproduction upon structures already so comjDlicated ! — But 

 if we turn away from mere fancies and consider the wonderful jDhenomena just 

 alluded to, in all their bearings, how instructive they appear with reference to this 

 very question of the influence of physical agents upon organized beings ! For here 

 we have animals endowed with the power of multiplying in the most extraordinary 

 ways, every species producing new individuals of its own kind, differing to the utmost 

 from their parents. Does this not seem, at first, as if we had before us a perfect 



^ Milxe-Edwards, Reeh. anat. et zool. f'aites pen- " Owf;N, Parthenogenesis, etc., q. a., p. 90. — BoN- 



dant un Voyage sur les cotes de Sicile, 3 vols. 4to. iig. net, (Ch.,) Traite d'Insectologie, etc., Paris, 1745. 



