ORGANIC EVOLUTION — THE FACTORS 57 



the infusorians do, by dividing the one into two or 

 more ; never do two or more cells unite to form another 

 cell, or by giving off living portions of their substance 

 unite, themselves maintaining their individual exist- 

 ences, to form in part or whole another cell — a germ 

 cell, for instance. The germ cells are therefore not 

 produced by other co-existing cells, but are co-descend- 

 ants with the other cells from a common ancestry. 

 Now if among mammals it is true that the cell-descend- 

 ants of a pair of conjuated germ cells do not conjugate 

 among themselves, nor emit portions of themselves 

 Avhich unite to form other cells, and it certainly is true 

 if we are to judge by what happens among unicellular 

 animals, among whom the behaviour of cells in this 

 respect can best be observed, it is impossible to under- 

 stand how acquired variations can be transmissible. 



To take an examj^lc already given : the muscles in 

 the blacksmith's arm are enlarged by exercise, i. e. the 

 muscle cells in the arm, when stimulated by exercise, 

 undergo proliferation and are so multiplied. Now if 

 the blacksmith's child is to inherit his acquired variation, 

 his germ cells, situated far distant from the muscle cells 

 of his arm, and related to them only through a remote 

 cell ancestry, must be so influenced, so structurally 

 altered, as to produce spontaneously in some of their 

 very remote cell-descendants (i. e. in the muscle cells 

 of the child's arm) that modification in point of numbers 

 which exercise temporarily produced in the muscle cells 

 of the blacksmith's arm. Is this possible ? 



I have heard it contended that the muscle cells 

 telegraph by means of the nerves, or in some other 

 way communicate what practically amounts to an order 

 to the germ cells to structurally modify themselves in 

 the desired way, but of course such a theory is too 

 absurd to be met with anything but derision. It is, 

 scientifically speaking, so utterly ridiculous as to be 



