H2 FOOT-NOTES TO EVOLUTION. 



modified the somatic protoplasm that, although they 

 may be fully developed as shown by sexual maturity, 

 they at once increase in size as soon as more abundant 

 food is provided, and this takes place by the active 

 growth and division of all the cells of the body. In 

 higher animals, once maturity has been reached, there is 

 little chance for growth, apparently because many of 

 the cells are so highly differentiated that they can no 

 longer divide; consequently the growth is limited, and 

 hence the size of the adult may depend in part upon the 

 amount of nutriment furnished to the embryo. This 

 limitation of growth is due to the high degree of dif- 

 ferentiation of the somatic cells. But as the germ 

 cells are not highly differentiated and are capable of di- 

 vision, it follows that they would not be permanently 

 modified by starving. It may be, as Professor Brewer 

 argues, that long-continued starving and consequent 

 dwarfing of animals may leave its mark on the germinal 

 plasm ; but, as he also remarks, this influence must be 

 very slight as compared with the cumulative effects of 

 selection in breeding, and it is safe to assert that there 

 is no such wholesale and immediate modification of the 

 germinal plasm due to the influence of nutrition as some 

 people seem to suppose. 



(b) The interesting experiments of Schmankewitsch 



in transforming one species of Artemia into another by 



gradually increasing the salinity of the 



water, or in transforming Artemia into 

 environment. 



another genus, Branchmecta, by decreas- 

 ing the salinity of the water, are well known and are 

 often cited as illustrations of the fact that specific and 

 even generic differences may suddenly be produced 

 under the influence of the environment. The very fact, 

 however, that these changes are suddenly produced, and 

 that they can at will be quickly modified in one direction 



