268 AGE, GROWTH, AND DEATH 



neous opinions I have deferred publication for a long time, during 

 which, however, no very essential improvement of the outline I 

 had drawn has occurred to me. To deal with such difficult and 

 dangerous questions with complete success requires more know- 

 ledge and judgment than I possess ; I hope, therefore, to be al- 

 lowed to publish what follows rather as opinions I deem plausible, 

 than as conclusions I believe certain. Of one thing, however, I 

 feel sure that it is useless to discuss the opposing claims of con- 

 scious automatism, the mechanical theory of life and a vital prin- 

 ciple, until we decide what are really the vital phenomena to be 

 explained. 



All the higher animals and plants are known to consist of col- 

 onies of cells. There are beside many unicellular animals and 

 plants. Of late years there have been described a large number 

 of organisms stated to consist solely of protoplasm. It is on these 

 discoveries that the various protoplasm theories of life have been 

 founded. Many popular articles have been written beginning 

 with the assertion that protoplasm is a simple, jelly-like mass, 

 and ending with the conclusion that life depends solely on the 

 mechanical properties of protoplasm. I think it cannot be too 

 seriously regretted that respectable periodicals have published so 

 many of such articles, because all but the ignorant know that 

 protoplasm is not jelly-like, and not simple ; on the contrary, it 

 consists of many and various chemical compounds, and from 

 recent investigations it has become probable that it never exists 

 as a homogeneous mass, but always contains numerous vacuoles, 

 each enclosing some distinct substance or substances, liquid or 

 solid ; this structure explains the appearance of the so-called 

 protoplasmatic network. Moreover, protoplasm probably can- 

 not permanently maintain its life when separated from a nucleus. 1 

 The number of protoplasmatic animals supposed to be without 

 nuclei has rapidly diminished, especially as the nucleus of the 



1 By this I mean only, that all vital functions cannot be performed, because 

 to some of them the nucleus is necessary. Of course protoplasm may remain 

 alive when separated from the nucleus, but the possibility of reproduction is 

 probably lost. 



