THE CELL AND HEREDITY. 17 



from unity and serenity to multiplicity and pain." 

 Was this "a gigantic mistake, a stupendous blunder 

 of the blind unconscious force from which there is no 

 escape until the world is hurled back into nothingness 

 by the supreme efforts of the human will " ? 



(2) Its beginning shown in conjugation of cells. 

 Exchange of experiences. Development of conjuga- 

 tion into the complex sex phenomena of the metazoa. 



Sexual cells in metazoa (many-celled or compound 

 animals). These primarily alike and like protozoa. 

 Become specialized by sex differentiation into: (a) 

 spermatozoa, mobile cells composed chiefly of nucleus ; 

 and (6) ova, sessile, immovable cells provided with 

 food yolk for the nourishment of the new cell struc- 

 tures. How a cell divides. Lengthwise splitting of 

 chromatin under influence of asters or attraction spheres. 

 Equal division ; never quite equal. 



Boveri's experiments. Transfer of nucleus from egg 

 to egg in echini. As the nucleus is, so is the result- 

 ant animal, whether developed in its own egg, or its 

 own protoplasm, or in that of another. 



Analogous transfer of nucleus in protozoa. The chro- 

 matin determines what the resultant animal shall be. 



Many-celled animals really compound. Edmund 

 B. Wilson's experiment with the lancelet. Division 

 of egg; when of two cells into two, each forms one 

 animal, half normal size ; division when segmented 

 into four forms four animals, each one-fourth size ; 

 division into eight, each cell seems a ciliated in- 

 fusorian, but dies before further division. Could be 

 true of all animals at all times were it not that mutual 

 aid induces mutual dependence. 



