268 DARWINISM TO-DAY. 



affected somatic parts. A high temperature or a moist at- 

 mosphere may modify the colour of the skin, change the pat- 

 tern of the body superficies, but will overheated germ-cells 

 produce new individuals showing the same changes of skin 

 colour and pattern if the same conditions of environment of 

 the soma are not repeated? How much less conceivable, 

 then, is the influencing of the germ-cells so as to compel 

 them to reproduce on daughter body-parts specific effects 

 produced on special parental body-parts by such specific and 

 localised influences as vigorous use of an arm, disuse of a 

 leg muscle, repeated contact of the palm of the hand with 

 hard bodies. Indeed, this lack of means of relating the 

 germ-plasm to the soma, the rest of the body, has stood 

 much in the way of any satisfactory conception of the phe- 

 nomena of heredity, that is, the reproduction by the germ- 

 cells of new individuals resembling the parental, and has 

 led to constant and thoughtful attention and speculation ever 

 since the time of Darwin ; indeed, from long before Dar- 

 win's time. 



One of the most favoured ways of attempting to explain 

 how the germ-cells can represent in their make-up, and 

 possess the capacity to develop into, the whole complex body, 

 has been to conceive of the giving off of small representa- 

 tive particles from all the cells of the body which should be 

 carried by the blood to the germ-plasm and deposited in the 

 germ-cells. The germ-cells in their development would 

 then, by virtue of this manifold representation, be able to 

 expand into the whole body during a shorter or longer 

 course of development and growth. This notion of the com- 

 position of the germ-plasm of micromeres collected from all 

 the somatic cells, is the conception at the basis of Buffon's 

 theory of "organic molecules," of Spencer's "physiological 

 units," Maggi's "plastidules," Altmann's "bioblasts," Wies- 

 ner's "plasomes," Darwin's "gemmules," Galton's "stirps," 

 Nageli's "micellae," Weismann's "biophors and determi- 



