142 The Mechanistic Conception of Life 



species call forth membrane formation in the sea-urchin egg. 

 An extract of the coecum of the star-fish was very effective. 



We have already mentioned the fact that the extract of 

 dead sperm of foreign species, e.g., of star-fish, certain mollusks, 

 certain worms, sharks, fowl, causes membrane formation in the 

 eggs of franciscanus. Experiments with the extract of dead 

 sperm of their owti species on the egg oi franciscanus or purpura- 

 tus fail; and the same is true for extracts from the tissues of 

 these species.^ What causes this difference in the action of 

 the lysins from their own and a foreign species ? We know 

 that the lysins of our o\^ti blood do not hurt our cells while 

 they hurt the cells of foreign species. There exists, therefore, 

 an immunity of the eggs as well as of the rest of the cells against 

 the lysins of their own blood or tissues. 



Our experiments throw a light upon the nature of this 

 immunity. If the lysins contained in our blood do not injure 

 our cells it can only be due to one of two facts: The lysins of 

 our own blood can either not diffuse into our cells, while they 

 can diffuse into the cells of foreign forms, or the cells contain 

 antibodies against the lysins of their own body, but not against 

 those of foreign species. As far as the lysins of the blood are 

 concerned we cannot decide between the two possibilities. 

 We can, however, reach a- decision for the lysins of the sperma- 

 tozoa. The extract from the dead sperm of the sea-urchin is 

 ineffective for the eggs of the sea-urchin solely for the reason 

 that it cannot diffuse into the sea-urchin egg. For if the sea- 

 urchin lysin is carried by the living sea-urchin spermatozoon 

 (which acts as a motor for the lysin) into the sea-urchin egg, 

 the lysin is very active and probably more active than the 

 lysin of foreign species. If the sea-urchin egg contained an 

 antibody against the lysin of the sea-urchin sperm, the sea- 

 urchin sperm should not be able to call forth membrane 

 formation when it enters the sea-urchin egg. 



1 If eggs were sensitized with SrCl^ they could be caused to develop by 

 extracts from the coeciun of the sea-urchin, though this was true only exceptionally. 



