CAUSE OF HEREDITY 275 



able to pass on continually from cell to cell every expe- 

 rience and tradition of the ages. A record is taken of the 

 past and preserved, and continually handed on to the next 

 generation. The following by Prof. Wilson will further 

 illustrate this and also show that the centrosome is the 

 intelligent directing center of the cell, and that if the nu- 

 cleus is disconnected no work will take place. He says : 

 "The interpretation of cleavage as a process of cell divi- 

 sion was followed by the demonstration that cell divi- 

 sion does not begin with cleavage, but can be traced back 

 into the foregoing generation, for the egg cell as well as 

 the sperm cell arises by. the division of the cell pre-exist- 

 ing in the parent body. It is therefore derived by direct 

 descent from an egg cell of the foregoing generation and 

 so on ad infinitum. 



"Extending backward from existing plant and animals 

 to that remote and unknown period when vital organiza- 

 tion assumed its present form, life is a continuous stream. 

 The individual body dies, it is true, but the germ cells 

 live on, carrying with them, as it were, the traditions of 

 the race from which they spring and handing them on to 

 their descendants." 



A peculiar thing takes place when the cell divides. The 

 granules in the nucleus line up in groups or strings which 

 are called chromosomes, which we see from the following 

 by Mr. Wilson are always of the same number in every 

 plant or animal or species of cell. He states: "The re- 

 markable fact has now been established with high prob- 

 ability that every species of plant or animal has a fixed 

 and characteristic number of chromosomes, which regu- 

 larly recur in the division of all of its cells, and in all 

 forms arising by sexual reproduction the number is even. 

 Thus in some of the sharks the number is 36, in certain 

 gastropods, it is 32 ; in the mouse, the salamander, the 



