12 THE POPULAR SCIENCE MONTHLY 



gins with the egg was of course unknown to primitive or pre-scientific 

 man. Death was assumed to be due to the departure of this " life prin- 

 ciple " from the body. 



Scientifically, however, individual life begins (in the case of the sea- 

 urchin and possibly in general) with the acceleration of the rate of 

 oxidation in the egg, and this acceleration begins after the destruction 

 of its cortical layer. Life of warm blooded animals — man included — 

 ends with the cessation of oxidation in the body. As soon as oxidations 

 have ceased for some time the surface films of the cells, if they contain 

 enough water and if the temperature is sufficiently high, become perme- 

 able for bacteria, and the body is destroyed by microorganisms. The 

 problem of the beginning and end of individual life is physico-chem- 

 ically clear. It is, therefore, unwarranted to continue the statement 

 that in addition to the acceleration of oxidations the beginning of 

 individual life is determined by the entrance of a metaphysical " 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. 



6. Heredity 



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 can 

 not 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, Ivupelwieser, Hagedoorn and Baltzer 

 were able to confirm. This fact has some bearing upon the further in- 

 vestigation 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 concerned, we 

 can say to-day that the view of those authors was correct who, with 

 Boveri, localized this transmission not only in the cell nucleus, but in a 



