IV THE CELL AND THE ORGANISM 63 



of the origin of embryos through repeated cell-divisions. And 

 finally a concentrated effort was made by many investigators 

 in many countries to discover in cell divisions and fusions, 

 and especially in the part played by the nucleus, the physical 

 mechanism of heredity. During this century the re-discov- 

 ery of Mendelism by De Vries and others, and the rise of the 

 new science of Genetics, have led to redoubled efforts to find 

 the explanation of the many peculiar phenomena of heredity 

 in an analysis of the parts played by the nucleus and the 

 other elements in the protoplasm of the cell, and at present 

 experimental cytology is being vigorously prosecuted with 

 numerous improved methods and appliances. 



Let us now consider the structure of the cell and the part 

 it plays in organisms. I shall only summarise its most 

 general and outstanding features, with a view to illustrating 

 the considerations and speculations which will be advanced 

 later. I am trying to find concepts for vital phenomena, 

 which will be coherent not only with those phenomena but 

 also with wider aspects of knowledge and reality, and a 

 reference to the scientific facts and results is therefore 

 necessary. The time is past when a philosophy of life could 

 be evolved without a knowledge of or reference to the 

 scientific facts and view-points. 



All plants and animals consist of cells, these cells being 

 again usually composed of various chemical substances, some 

 of which have a very complex constitution. The number of 

 cells in an organism varies according to its size and com- 

 plexity, some of the lowest, most primitive organisms being 

 unicellular or composed of comparatively few cells, while at 

 the other end the higher plants and animals may contain 

 untold millions of cells. The human brain alone is estimated 

 to have about 9000 million cells! These cells again are of 

 a most diverse character, the cells which build up the various 

 parts and organs of the body being different from each other. 

 Thus the cells of the nerves and the bones and the 

 muscles and indeed of all parts of the animal organism differ 

 markedly from each other, and the number of the different 

 kinds of cells that go to the making up of a body may be 



