SUFFICIENCY OF EVIDENCE. 35 I 



is a scientific " hypothesis" but that it still requires to be 

 "proved." When these remarks are made by persons who 

 do not possess the requisite empirico-philosophical culture, 

 nor the necessary knowledge in comparative anatomy, em- 

 bryology, and palaeontology, we cannot be much offended, 

 and we refer them to the study of those sciences. But 

 when similar remarks are made by acknowledged special- 

 ists, by teachers of zoology and botany, who certainly ought 

 to possess a general insight into the whole domain of their 

 science, or who are actually familiar with the facts of those 

 scientific domains, then we are really at a loss what to 

 say. Those who are not satisfied with the treasures of our 

 present empirical knowledge of nature as a basis on which 

 to estabKsh the Theory of Descent, will not be convinced 

 by any other facts which may hereafter be discovered ; 

 for we can conceive no circumstances which would furnish 

 stronger or a more complete testimony to the truth of the 

 doctrine of filiation than is even now seen, for example, in 

 the well-known facts of comparative anatomy and ontogeny. 

 I must here again direct attention to the fact, that all the 

 great and general laws, and all the comprehensive series 

 of phenomena of the most different domains of biology can 

 only be explained and understood by the Theory of Develop- 

 ment (and especially by its biological part, the Theory of 

 Descent), and that without it they remain completely inex- 

 plicable and incomprehensible. The internal causal con- 

 nection between them all proves the Theory of Descent to 

 be the greatest inductive law of Biology. 



Before concluding, I will once more name all those series 

 of inductions, all those general laws of Biology, upon which 

 this comprehensive law of development is firmly based. 



