372 Appendix 
One feature of special interest to us is the fact that 
the new conditions of the environment to which the 
animal gradually becomes accustomed tend in time to 
become his optimum. “This individual adaptation 
(e. g., to a different proportion of salt) is effected in 
accordance with the rule that the conditions of density 
under which an individual is living, tend to become in 
time the optimum conditions for that individual.” 4 
This may be observed even in plant organisms. 
Plasmodia of the Myxomycetes die when plunged sud- 
denly into 1 or 2% glucose solutions, and even draw 
back from % or 4% solutions, and yet they may 
gradually become accustomed to 2% solutions so that 
they finally show by their behavior that they prefer their 
new environment to the original one without glucose.!? 
The diatom Navicula brevis ordinarily shuns even 
the weakest light and tries to hide itself in the darkest 
part of the drop of water in which it is being observed. 
However, if a culture is placed in the bright light of a 
window for two weeks, it exhibits exactly the opposite 
tendency and makes for the brightest part of the drop 
as soon as it is removed again to its former position in 
a weak light.78 
The common actinian (Actinia equina) often found 
clinging to rocks in all possible positions with relation to 
the force of gravity, sometimes with the axis of the 
tion of Organisms to High Temperatures.”—Archives fiir. Entw.- 
Mech. der Organismen, II, 2. Heft, July, 1895—C. B. Davenport 
and R. V. Neal, “On the Acclimatisation of Organisms to Poisonous 
Chemical Substances,” loc. cit., II, 4. Heft, Jan. 18096. 
11Davenport and Castle, op. cit., p. 241. 
12K. Stahl, “Zur Biologie der Myxomyceten,”’ Bot. Zeit., Mar. 
7, 14 and 21, 1884, p. 166. 
13Davenport and Castle, op cit., p. 246. 
