296 American Quarterly Microscopical Journal. 



is a reply to Prof. Virchow's address before the German Associa- 

 tion at Munich in 1877, in which the author states clearly, and 

 with much vigor, the reasons for his dissent from Virchow's posi- 

 tion, and enunciates with the distinctness characteristic of 

 Hackel, the advanced views he advocates. In this controversy, 

 Virchow's opinion is the more conservative, while Hackel, sure of 

 his position, permits no doubt or question to weaken his convic- 

 tions. Truth will ultimately evolve from the conflict of warring 

 theories. An implicit acquiescence in modern views, or stagna- 

 tion of thought concerning the great questions which science is 

 presenting for solution, is manifestly unwise. Hence, the value of 

 such antagonisms ; for each advocate, in endeavoring to pierce 

 the logic of facts of which his opponent makes an armor, adds, 

 perhaps unwittingly, to the sum total of human knowledge — casts 

 a stone upon the burial-heap of ignorance and idle conjecture. 



Briefly, Virchow took exception to Hackel's positive assertion 

 of the truth of Darwinism, or natural selection, holding it to be 

 as yet an "unproved hypothesis" and questioning the propriety of 

 teaching anything the certainty of which is not absolutely de- 

 monstrated, anything subjective in its character as opposed to 

 the external or objective ; the latter to be the only mental diet of 

 learners in the schools. Naturally, this stimulated Hackel to reply. 

 And he does it with cogent reasoning, grim humor and caustic 

 irony. We will attempt to outline his argument. 



The progress of the evolution theory, says Hackel, has been 

 greatly advanced by the fact that there are but two alternatives 

 from which to choose, either that of natural development, or of 

 supernatural creation. He defines the universal theory of evolu- 

 tion, Monism; the theory of descent, Transformism, explaining the 

 origin of organic species by transformation; the theory of selection, 

 Darwinism, at present the most important, but by no means the 

 only one. These several theories, according to Hackel, are con- 

 tinually and unwittingly confused with each other. Doubtless, 

 many imperfectly known causes have been of importance in 

 effecting the origin of species, and the judgment of naturalists 

 will differ as to the value of each; but this does not affect the 

 validity of the general doctrine of descent, the only rational 

 one. The proofs of this doctrine, Hackel considers, are suffi- 

 cient, and will never be stronger ; they are valuable because 

 deduced from the totality of biological phenomena, not from this 

 or that single observation. 



