138 The Mechanistic Conception of Life 



protoplasm of the egg as soon as it comes in contact with it. 

 In this way almost simultaneously both substances of the 

 spermatozoon become effective, the cytolytic substance, which 

 causes the membrane formation, and the ''corrective" substance. 

 The experiments, however, result differently when we add the 

 spermatozoa of a foreign species, e.g., star-fish, to the egg of 

 the sea-urchin. Under ordinary conditions sperm of the star-fish 

 cannot cause the egg of the sea-urchin to develop; it becomes 

 effective, however, in sea- water which has been rendered a little 

 more alkaline through the addition of some NaHO. If 0.6 c.c. 

 n/10 NaHO is added to 50 c.c. of sea- water all the eggs of the 

 sea-urchin form fertilization membranes in such a mixture if 

 only a trace of living sperm of a star-fish {Asterias ochracea) is 

 added. It takes, however, some time, mostly from ten to fifty 

 minutes, until the living star-fish sperm brings about this effect; 

 while after the addition of sea-urchin sperm this result is 

 obtained in one minute. 



If the sea-urchin eggs, all of which have formed membranes 

 upon the addition of living star-fish sperm, are put back into 

 normal sea-water and if we watch their further fate, we soon 

 notice that we are dealing with two groups of eggs. The one 

 group acts as if only one of the two agencies, namely, the 

 cytolytic one, had taken effect. These eggs show at room 

 temperature only the beginning of nuclear division and then 

 disintegrate, while at a lower temperature they may develop a 

 little farther. If we treat them, however, after the membrane 

 formation by star-fish sperm for from thirty to fifty minutes 

 with a hypertonic solution they all develop at room temperature 

 mostly into normal larvae. The other eggs develop without 

 any subsequent treatment with a hypertonic solution into 

 normal larvae. 



What causes this difference in the behavior of both groups 

 of eggs ? A histological examination of these eggs decides this 

 point. My assistant, Mr. Elder, found that a spermatozoon 



