On the Origin of Species, 119 



I believe tliat animals have descended from at most only four or 

 five progenitors, and plants from an equal or lesser number. 



" Analogy would lead me one step further, namely, to the 

 belief that all animals and plants have descended from some one 

 prototype. But analogy may be a deceitful guide. Neverthe- 

 less all living things have much in common, in their chemical 

 composition, their germinal vesicles, their cellular structure, and 

 their laws of growth and reproduction. We see this even in so 

 trifling a circumstance as that the same poison often similarly 

 affects plants and animals ; or that the poison secreted by the 

 gall-fly produces monstrous growths on the wild rose or oak-tree. 

 Therefore I should infer from analogy that probably all the or- 

 ganic beings which have ever lived on this earth have descended 

 from some one primordial form, into which life was first 

 breathed." 



We may well ask what is gained by such a result, even if 

 established. The origin of species, as we now have them, it is 

 true is mysterious, but what is gained by reducing them all to 

 one primitive form ? That would be an equal mystery, more 

 especially if it included within itself the germs of all the varied 

 developments of animal and plant life. By such a doctrine also 

 we involve ourselves in a host of geological and other difiiculties, 

 and so break down the distinction between species and varieties 

 as to deprive our classifications of any real value. On the con- 

 trary, if we are content to take species as direct products of a 

 creative power, without troubling ourselves with supposed secon- 

 dary causes, we may examine, free of any trammelling hypothesis, 

 the law of their succession in time, the guards placed upon their 

 intermixture, the limits set to their variation in each case, the 

 remarkable arrangements for diminishing variations by the natural 

 crossing of varieties, the laws of geographical distribution from 

 centres of origin, and the physical causes of variation, of degene- 

 racy, of extinction. 



All these are questions to be investigated apart from any hypo- 

 thesis of the common origin of different species on the one hand, 

 or of the diverse origin of individuals apparently identical on the 

 other ; and we cannot doubt that the results will approach to the 

 following conclusions. (1) That the origin of specific distinctness 

 lies beyond the domain of any natural law known to us. (2) That the 

 variations of the species are the effects of the combined influences 

 of its natural endowments and of external circumstances. (3) That 



