416 PROGRESS OF SCIENCE IN THE CENTURY. 



The germ-plasm is in a sense so apart that it is diffi- 

 cult to conceive of the mechanism by which it might 

 be influenced in a specific or representative manner 

 by changes in the cells of the body. 



A General Argument For. — We have recognised 

 that the germ-cells may be early set apart in the 

 building up of the body, and that they sometimes 

 seem scarcely to share at all in its daily life. On 

 the other hand, in many plants the distinction be- 

 tween body and germ-cells can hardly be drawn, and 

 even if we keep to animals the bonds between the 

 body and its germ-cells are often very close. The 

 blood and lymph or other body fluids form a common 

 medium for all the parts of the animal; alteration 

 of diet in the early youth of some animals like tad- 

 poles and caterpillars may determine the predomi- 

 nance of one sex or the other through influences 

 which must pass from body to germ-cells; various 

 poisons may affect the whole bodily system and the 

 germ-cells as well, and there are real though dimly 

 understood correlations between the reproductive sys- 

 tem and the rest of the body. It is therefore erro- 

 neous to think of the germ-cells as if they led a 

 charmed life uninfluenced by any of the accidents 

 and incidents in the daily life of the body which 

 bears them. ISTo one believes this, Weismann least of 

 all, for he finds one of the chief sources of congenital 

 variation in the nutritive stimuli exerted on the 

 germ-plasm by the varying state of the body. 



There are some who find in this " a concealed 

 abandonment of the central position of Weismann,^' 

 and one of them has recently put the argument thus : 

 if the germ-plasm is affected by changes in nutrition 

 in the body, and if acquired characters affect changes 

 in nutrition, then " acquired characters or their con- 



