ORIGIN OF ADAPTATIONS AND OF SPECIES 243 
tion. This progressive acclimatization of successive genera- 
tions of an organism to heat is clearly due in large measure to 
heredity. So also in the case of the entomostracan Artemia, 
whose specific form Schmankewitsch succeeded in changing, 
by increasing the salinity of the water in which the animal 
lived. Here, again, the adaptation was brought about with- 
out the aid of selection. 
Poulton’s already-mentioned experiments on larvee and 
pupze show that these may become protectively colored as the 
direct effect of the surrounding light on the organism. Here, 
of course, the possible influence of natural selection can scarcely 
be excluded, though the fact remains that the color resem- 
blances are initiated directly by the stimulus of hght upon 
protoplasm. 
Protoplasm itself is to a certain extent adaptive, in that it 
may become acclimatized to untoward conditions of heat, light 
and other stimul. From this point of view, Henslow’s theory 
of self-adaptation in plants deserves more consideration than 
it has received, though Henslow did not adopt the theory of 
natural selection. 
Blastogenic Variations.—According to Weismann, only 
congemtal variations are inheritable, 1. e.,.only those that result 
from modifications of the germ plasm. He holds that while 
all variations are due ultimately to external influences, the 
processes of reproduction (conjugation in unicellular, and 
sexual reproduction in multicellular organisms) furnish fresh 
combinations of individual variations for the operation of nat- 
ural selection, and that this is the chief purpose of amphimixis, 
or “the mingling of two individuals or of their germs.” 
Inheritance of Acquired Characters.—\Veismann and his 
followers, in opposition to the Neo-Lamarckians, hold that 
somatogenic, or acquired, characters are not transmissible; 
that every permanent (hereditary) variation proceeds from 
the germ. 
The subject of the inheritance of acquired characters has 
aroused no end of discussion, much of which has been fruit- 
