with the fact that organisms form a progressive series from 

 the simple to the more complex, and with the observed 

 phenomena of individual development, lead me to regard 

 the concept of Descent as admissible, and in a certain 

 sense, even probable. But I agree with Fleischmann in 

 saying that this is a mere belief, and that all attempts to 

 give it a higher scientific value by inductive proof have 

 signally failed. 



My standpoint, moreover, requires me to admit the 

 validity of the hypothesis of Descent as an heuristic maxim 

 of natural science. I believe that we shall be justified in 

 the future, as we were forty years ago, in directing our in- 

 vestigation in the direction of Descent, and I do not con- 

 sider such investigation so utterly hopeless as Fleischmann 

 represents it. However, I entirely concur with him in the 

 opinion that we are here concerned (and shall be for a long 

 time to come) with a mere hypothesis which belongs not in 

 the market-place, nor among the world views of the mul- 

 titude, but in the study of the man of science. 



Above all it must not be mixed up with religious ques- 

 tions. Whether the hypothesis will ever emerge from the 

 study of the man of science as a well-attested law, is still. 

 an open question, incapable of immediate solution. 



It is of interest for us to inquire what reception 

 Fleischmann's protest against the theory of Descent has 

 been accorded by his associates. 



Fleischmann was formerly an advocate of the theory 

 of Descent. He was a pupil and assistant of Selenka, who- 



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