12 The Mechanistic Conception of Life 



in my method of artificial parthenogenesis; namely, by carry- 

 ing two substances into the egg, one of which acts like the 

 butyric acid and induces the membrane formation, while 

 the other acts like the treatment with a hypertonic solution 

 and enables the full development of the larvae. In order to 

 prove this for the sea-urchin egg foreign sperm, e.g., that of 

 the star-fish, must be used. The sperm of the sea-urchin 

 penetrates so rapidly into the sea-urchin egg that almost 

 always both substances get into the egg. If, however, star- 

 fish sperm is used for the fertilization of the sea-urchin egg, 

 in a large number of cases, membrane formation occurs 

 before the spermatozoon has found time to penetrate entirely 

 into the egg. In consequence of the membrane formation 

 the spermatozoon is thrown out. Such eggs behave as if 

 only the membrane formation had been caused by some 

 artificial agency, e.g., butyric acid. They begin to develop, 

 but soon show signs of disintegration. If treated with a 

 hypertonic solution they develop into larvae. In touching 

 the egg contents the spermatozoon had a chance to give off 

 a substance which liquefied the cortical layer and thereby 

 caused the membrane formation by which the further 

 entrance of the spermatozoon into the egg was prevented. 

 If, however, the star-fish sperm enters completely into the 

 egg before the membrane formation begins, the spermatozoon 

 carries also the second substance into the egg, the action of 

 which corresponds to the treatment of the egg with the hyper- 

 tonic solution. In this case the egg can undergo complete 

 development into a larva. 



F. Lillie has recently confirmed the same fact in the egg 

 of a worm. Nereis. He mixed the sperm and eggs of Nereis 

 and centrifuged the mass. In many cases the spermatozoa 

 which had begun to penetrate into the egg were thrown off 

 again. The consequence was that only a membrane forma- 

 tion resulted without the spermatozoon penetrating into the 



