228 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



suggest what may be the nature of the second factor in the 

 spermatozoon. The "lysin'' of the spermatozoon serves for 

 the production of membrane formation. The second factor 

 serves to turn the development into the right direction by the 

 suppression of the tendency to disintegrate. 1 



2. A second proof for the fact that the spermatozoon causes 

 the development of the egg by two agencies, one of which causes 

 merely membrane formation, is contained in the following facts. 

 The eggs of S. franciscanus can be more easily caused to form 

 membranes than the eggs of S. purpuratus. I found in 1908 and 

 1909 that if we add living spermatozoa of the shark or of fowl 

 to such eggs, the eggs form membranes. 2 In the case of the 

 spermatozoa of the shark it was possible to wash them first 

 repeatedly in sea-water and thus free them from all blood or 

 lymph. Nevertheless, the eggs of S. franciscanus formed ferti- 

 lization membranes upon contact with the living spermatozoa 

 of the shark. Such eggs, when left to themselves, began to 

 segment but very soon disintegrated. If they were, however, 

 treated afterward with a hypertonic solution they developed 

 into larvae. The explanation of this fact is that the living 

 heterogeneous spermatozoon upon contact with the egg gives 

 off to the latter the membrane-forming substance, without 

 supplying the corrective effect. 



A third proof lies in the fact, mentioned in a previous chap- 

 ter, that the watery extract of foreign sperm calls forth the mem- 

 brane formation in the same way as butyric acid does without 

 supplying the second corrective factor. 



3. I have tried in vain to separate in the same way the 

 membrane-forming substance from the living sperm of the sea- 



1 In order to test this idea further I asked Dr. Elder to make a cytological 

 examination of these eggs. He found that when only a few eggs of S. purpuratus 

 which had formed membranes developed into larvae a small percentage showed 

 the sperm nucleus; while the other eggs had no sperm nucleus although they had 

 formed a membrane. 



Loeb, Address at the International Congress of Medicine, Budapest, 1909; 

 reprinted in The Mechanistic Conception of Life, 1912. 



