892 The American Naturalist. [November, 
is reached the demand for new materials in growth ceases, the 
wear and tear of the system is diminished with less intense 
demands for the processes of repair. With this falling off in 
the requirements of the organism for katabolic products includ- 
ing energy, anabolism predominates and protoplasm is allowed 
to accumulate in the different organs from the check to destruc- 
tive metabolism arising from the general decline of vital 
activities. 
The hypothesis that the germ plasma, or the reproductive 
granules it contains, are immortal and entirely independent 
of the body-plasma, on which is based the assumption that 
acquired characters cannot be transmitted, appears to be in 
direct conflict with these physiological laws of nutrition. The 
protoplasm of the body presents, as we have seen, many differ- 
entiated varieties, adapted to the specific function of each 
organ, and its katastates differ accordingly. The various 
glandular secretions, the products of nervous and muscular 
activities, the numerous excretory products, and even the 
germ cells so far as their molecular structure is concerned 
must be considered as katastates of the protean varieties of 
protoplasm. The so-called body plasma must then be looked 
upon as made‘up of many differentiated subdivisions, in gen- 
etic relations with many katabolic products, all of which are 
correlated, through vital activities, to act in harmony to serve 
the entity we recognize as the individual. 
The differentiation of a germ-plasma especially concerned 
in the function of reproduction must be accepted as a physio- 
logical factor of the first importance, but we are not warranted 
in assuming that it is exempt from the metabolic transforma- 
tions that characterize other living substances. 
Herbert Spencer defines life as “ the continuous adjustment 
of internal relations to external relations;’ and Dr. Foster 
expresses substantially the same conception in defining 
living substance as “not a thing or body of a particular 
chemical composition, but matter undergoing a series of 
changes.” These definitions fairly represent our present 
knowledge of vital activities. Metabolism with its “sim- 
ultaneous and successive” phases of anabolic and kata- 
