The Mechanistic Conception of Life 15 



individual life is determined by the entrance of a meta- 

 physical "life principle" into the egg; and that death is 

 determined, aside from the cessation of oxidations, by the 

 departure of this "principle" from the body. In the case of 

 the evaporation of water we are satisfied with the explanation 

 given by the kinetic theory of gases and do not demand that 

 — to repeat a well-known jest of Huxley — ^the disappearance 

 of the "aquosity" be also taken into consideration. 



VI. HEKEDITT 



It may be stated that the egg is the essential bearer of 

 heredity. We can cause an egg to develop into a larva 

 without sperm, but we cannot cause a spermatozoon to 

 develop into a larva without an egg. The spermatozoon 

 can influence the form of the offspring only when the two 

 forms are rather closely related. If the egg of a sea-urchin 

 is fertilized with the sperm from a different species of sea- 

 urchin, the larval form has distinct paternal characters. If, 

 however, the eggs of a sea-urchin are fertilized with the sperm 

 of a more remote species, e.g., a star-fish, the result is a sea- 

 urchin larva which possesses no paternal characters, as I 

 found and as Godlewski, Kupelwieser, Hagedoorn, and 

 Baltzer were able to confirm. This fact has some bearing 

 upon the further investigation of heredity, inasmuch as it 

 shows that the egg is the main instrument of heredity, while 

 apparently the spermatozoon is restricted in the transmission 

 of characters to the offspring. If the difference between 

 spermatozoon and egg exceeds a certain limit the hereditary 

 effects of the spermatozoon cease and it acts merely as an 

 activator to the egg. 



As far as the transmission of paternal characters is con- 

 cerned, we can say today that the view of those authors was 

 correct who, with Boveri, localized this transmission not only 

 in the cell nucleus, but in a special constituent of the nucleus. 



