372 Appendix 1 



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." n 



This may be observed even in plant organisms. 

 Plasmodia of the Myxomycetes die when plunged sud- 

 denly into i or 2% glucose solutions, and even draw 

 back from l /> or J4% 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. 12 



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. 13 



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 fur. 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. 1896. 



11 Davenport and Castle, op. cit., p. 241. 



12 E. Stahl, "Zur Biologic der Myxomyceten," Bot. Zeit., Mar. 

 7, 14 and 21, 1884, P- J 66- 



13 Davenport and Castle, op cit., p. 246. 



