Nature of the Process of Fertilization 123 



statements. The next question that should be raised would be 

 whether the spermatozoa act in the same way. It is true that 

 the spermatozoon contains a considerable proportion of salts, 

 especially KgPO^, but it may contain enzj-mes or it may con- 

 tain substances which have similar effects upon the physical 

 qualities of the colloids, like the three agencies mentioned above. 

 In the last volume of these lectures I pointed out that it is 

 impossible to derive all the various elements that constitute 

 heredity from one and the same condition of the egg.^ Our 

 recent experiments suggest the possibility that different con- 

 stituents of the egg are responsible for the process of fertiliza- 

 tion and for the transmission of the hereditary qualities of the 

 male. While we are able to produce the process of fertilization 

 by a treatment of the unfertilized egg with certain salts in 

 certain concentrations, we cannot hope to bring about the 

 transmission of the hereditary qualities of the male by any such 

 treatment. Hence, the inference must be that the transmis- 

 sion of the hereditary qualities of the male and the agency that 

 causes the process of fertilization are not necessarily one and 

 the same thing. I consider the chief value of the experiments 

 on artificial parthenogenesis to be the fact that they transfer 

 the problem of fertilization from the realm of morphology 

 into the realm of physical chemistry .^ 



1 Loeb, J., " The Heredity of the Markmg in Fish Embryos," Woods Hole Biol. 

 Led., Boston, 1899. 



2 This paper was written immediately after I had succeeded in producing 

 larvae from the unfertilized egg. In the following years the methods of artificial 

 parthenogenesis were improved and this led to the unraveling of the mechanism 

 by which the spermatozoon causes the egg to develop. An account of this work 

 is given in the two following papers. 



