10 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



The most remarkable fact, however, is this: that it is 

 possible to cause artificial parthenogenesis in eggs which are 

 refractory to any other method of artificial parthenogenesis. 

 All attempts to cause artificial parthenogenesis in the eggs of 

 Cumingia, a marine mollusc, had failed. But Mr. Wasteneys 

 and the writer found in 1912 that these eggs can be caused 

 to develop into larvae if they are treated with ox blood or 

 serum. In order to accomplish this they must first be sensitized 

 by a treatment with a solution of SrCl 2 . The writer had 

 previously found that sea-urchin eggs which cannot be caused 

 to form membranes under the influence of ox serum will 

 do so if they are first treated for some time with a solution 

 of SrCl 2 . 



Not only foreign blood but the extract of foreign cells is 

 efficient in inducing membrane formation and development in 

 the unfertilized egg. Blood of the species to which the eggs 

 belong is, however, entirely ineffective for this purpose. This 

 is analogous to the fact that foreign "lysins" may destroy the 

 cells of an animal while the cells are immune against the lysins 

 of their own species. The experiments on artificial partheno- 

 genesis indicate that this immunity is due to the fact that the 

 lysins are prevented from diffusing into the cells of the same 

 species while they can diffuse into the cells of foreign species. 



6. The question may next be raised whether the spermato- 

 zoon also effects membrane formation by means of a cytolytic 

 substance, a "lysin," and whether, in that event, it must carry 

 into the egg yet another substance besides the lysin for the 

 purpose of preventing the disintegration following membrane 

 formation. This is what actually appears to be the case. 

 Ten years ago I discovered a method of fertilizing the eggs of the 

 sea-urchin with the sperm of widely different species, e.g., of 

 the starfish. In employing this method, I found that not al! the 

 eggs of the sea-urchin which form membranes with (living) star- 

 fish sperm develop. Some of the eggs form membranes and 



