ARTIFICIAL PRODUCTION OF NORMAL LARV^: 543 



enzymes or other material. The ions and not the nncleins 

 in the spermatozoon are essential to the process of fertiliza- 

 tion (which may interest those who believe with me that 

 physiologists ought to pay a little more attention to inorganic 

 chemistry). I have no doubt that the same principles hold 

 good for the process of fertilization of other, if not all, the 

 marine animals, although the ions involved will probably 

 differ in various species. 



Finally we may ask the question, whether we may expect 

 to produce artificial parthenogenesis in mammalians. Jan6sik 

 has found segmentation in the unfertilized eggs of mam- 

 malians. This is similar to the fact mentioned above, that 

 the unfertilized eggs of sea-urchins may show a segmenta- 

 tion if they stay long enough in the sea-water. I consider 

 it possible that only the ions of the blood prevent the 

 parthenogenetic origin of embryos in mammalians, and I 

 think it further not impossible that a transitory change in 

 the ions of the blood may also allow complete partheno- 

 genesis in mammalians. 



