GENERAL KNOWLEDGE NEEDFUL. 345 



only by long- enduring transmission, by inheritance of 

 acquired adaptations of the brain, out of originally empiric 

 or experiential "knowledge a posteriori" (vol. i. p. 31). 



The objections to the Theory of Descent here discussed 

 and refuted are, I believe, the most important which have 

 been raised against it; I consider also that I have sufficiently 

 proved to the reader their futility. The numerous other 

 objections which besides these have been raised against the 

 Theory of Development in general, or against its biological 

 part, the Theory of Descent in particular, arise either from 

 such a degree of ignorance of empirically established facts, 

 or from such a want of their right understanding, and from 

 such an incapacity to draw the necessary conclusions, that 

 it is really not worth the trouble to go further into the 

 refutation. There are only some general points in regard 

 to which, I should like, in a few words, to draw attention. 



In the first place I must observe, that in order thoroughly 

 to understand the doctrine of descent, and to be convinced 

 of its absolute truth, it is indispensable to possess a general 

 knowledge of the whole of the domain of biological phe- 

 nomena. The theory of descent is a biological theory, and 

 hence it may with fairness and justice be demanded that 

 those persons who wish to pass a valid judgment upon it 

 should possess the requisite degree of biological knowledge. 

 Their possessing a special empiric knowledge of this or that 

 domain of zoology or botany, is not sufficient ; they must 

 possess a general insight into the whole series of phenomena, 

 at least in the case of one of the three organic kingdoms. 

 They ought to know what universal laws result from the 

 comparative morphology and physiology of organisms, but 

 more especially from comparative anatomy, from the indi- 



