I1I2 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. 
(4) 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 
another genus, Branchinecta, 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 
Changes in 
environment. 
