24 The Mechanistic Conception of Life 



whole " by which an organism becomes possible. In the answer 

 to this question the metaphysician finds an opportunity to put 

 above the purely chemical and physical processes something 

 specific which is characteristic of life only: the "Zielstrebigkeit," 

 the "harmony" of the phenomena, or the "dominants" of 

 Reinke and similar things. 



With all due personal respect for the authors of such terms 

 I am of the opiaion that we are dealing here, as in all cases of 

 metaphysics, with a play on words. That a part is so con- 

 structed that it serves the "whole" is only an unclear expression 

 for the fact that a species is only able to live— or to use Roux's 

 expression — ^is only durable, if it is provided with the automatic 

 mechanism for self-preservation and reproduction. If, for 

 instance, warm-blooded animals should originate without a 

 circulation they could not remain alive, and this is the reason 

 why we never find such forms. The phenomena of "adapta- 

 tion" cause only apparent difficulties since we rarely or never 

 become aware of the numerous faultily constructed organisms 

 which appear in nature. I will illustrate by a concrete example 

 that the number of species which we observe is only an infinitely 

 small fraction of those which can originate and possibly not 

 rarely do originate, but which we never see since their organiza- 

 tion does not allow them to continue to exist long. Moenk- 

 haus found ten years ago that it is possible to fertilize the egg 

 of each marine bony fish with the sperm of practically any 

 other marine bony fish. His embryos apparently lived only 

 a very short time. This year I succeeded in keeping such 

 hybrid embryos between distantly related bony fish alive for 

 over a month. It is, therefore, clear that it is possible to cross 

 practically any marine teleost with any other. 



The number of teleosts at present in existence is about 

 10,000. If we accomplish all possible hybridizations 100,000,000 

 different crosses will result. Of these teleosts only a very small 

 proportion, namely about one one-himdredth of 1 per cent. 



