Nature of the Process of Fertilization 115 



compounds in the egg and the spermatozoa. I do not l^eheve 

 that this objection is valid. We know that simple variations 

 in the configuration of a molecule have an enormous effect upon 

 life phenomena. This is showTi among others by the work of 

 Emil Fischer on the relation between the molecular configura- 

 tion of sugars and their fermentability. When Miescher made 

 his experiments he was not familiar with such possibilities. 

 Moreover, Miescher was not able to state whether the 

 spermatozoa contain enzymes or not. 



A third theory was a physical theory (Bischof). This 

 theory assumes that a peculiar condition of motion exists in 

 the spermatozoon which is transmitted to the egg and causes 

 its development. It should be said, however, that this idea 

 is not so very different from the chemical conception, because 

 it assumes exactly the same for the spermatozoon that Liebig 

 assumes for the enzj^mes. Liebig thought that the enzymes 

 owed their power of producing fermentation to the motions of 

 certain atoms or groups of atoms. 



The fourth conception is the stimulus conception, which 

 was originated by His. According to this conception the egg is 

 considered as a definite machine which if once womid up will 

 do its work in a certain direction. The spermatozoon is the 

 stimulus which causes the egg to undergo its development. It 

 is to be said in connection with this stimulus conception that 

 the main point at issue is omitted as to whether the stimulus 

 carried by the spermatozoon is of a physical or a chemical 

 character, and in this way, of course, the stimulus conception is 

 nothing but a disguised repetition of the chemical or physical 

 theory of fertilization. 



All these theories are so vague that we do not need to be 

 surprised that none of them has led to any further discovery. 

 If we want to make new discoveries in biology, we must start 

 from definite facts and observations, and not from vague 

 speculations. Among these observations the most important 



