THE president's ADDRESS. 347 



life-history, as a whole, of the organism. There are many data 

 both of observation and experiment which indicate that the 

 chromatin-grains are of primary importance in the life and vital 

 processes of organisms of all kinds. In the first place, the 

 chromatin-grains appear to be invariably present in every living 

 organism, and there are some organisms which consist of little or 

 nothing but chromatin. When a cell or a simple living organism 

 reproduces itself by the ordinary method that is to say, by divid- 

 ing into two or more daughter-individuals the chromatin-grains 

 divide also and are distributed amongst the offspring. In many 

 cells the nucleus divides by a very elaborate mechanism, termed 

 karyokinesis or mitosis, which ensures that of the two daughter- 

 nuclei produced, each obtains one of the two daughter-grains of 

 chromatin resulting from the division of each grain of chromatin 

 that was contained originally in the nucleus of the parent-cell. 

 And note this most remarkable fact of all : the sexual process, 

 that great mystery of living matter, consists essentially, in all 

 cases without exception, in plants and animals alike, of union of 

 nuclei or chromatin from two distinct organisms. In the whole 

 series, from man to sea-anemones and Protozoa, what are termed 

 commonly affairs of the heart are in reality affairs of the chromatin- 

 substance. The observed facts of fertilisation and development 

 have led to the belief, I might almost say the conviction, in the 

 minds of many naturalists that the chromatin-gi*ains determine 

 the characters of the offspring and are the bearers of hereditary 

 tendencies and properties. Finally it should be mentioned that 

 the special physiological function of the nucleus in the ordinary 

 life of the cell appears to be that of producing the peculiar sub- 

 stances known as ferments or enzymes, substances which more 

 than any others are characteristic of living bodies and of vital 

 activities. 



Equally remarkable are the results obtained by experiment. 

 If unicellular organisms are cut into smaller parts, it is found 

 that any part which does not contain the nucleus or a part of 

 the nucleus may continue living for a short time, but dies sooner 

 or later, and is incapable of feeding or growing and consequently 

 cannot regenerate the lost parts of the organism. A portion of 

 the protoplasm that contains no nucleus may exhibit for a time a 

 certain amount of movement, and may continue to digest food- 

 particles of which the digestion was begun before it was cut off 



