1909.] NATURAL SCIENCES OF PHILADELPHIA. 107 



grow where this could not be, seeking and occupying certain kinds of 

 soil and demanding certain amounts of moisture and avoiding situa- 

 tions where these were wanting. " In connection with the experiments 

 which have preceded, some experimental data from other sources should 

 be given in order to prove that organisms can be acclimated, that is 

 can be inured or habituated to conditions at first injurious to them. 

 A reference to the short bibliography of acclimatization at the end of 

 this paper will enable the investigator to obtain the additional evidence 

 of acclimatization which it is not possible to review. The experimental 

 data for animals and plants is here given. 



General Experimental Work on Acclimatization. 



Among invertebrates Loew 8 has found in Owen's Lake, California, 

 the alkaline waters of which contain among other things 2.5% of Na 2 C0 3 , 

 numerous living infusoria, Copepoda, larva? of Ephydra and molds. 

 Again the vinegar eel, Rhabditis aceti, lives in a 4% solution of acetic 

 acid, although this strength is usually fatal: e. g., a 0.23% solution of 

 acetic acid kills the tentacles of Drosera, according to Darwin. Beu- 

 dant accustomed fresh-water animals to salt water. He used Lymnea, 

 Physa, Planorbis, Ancyclus, Paludina and some other fresh-water 

 mollusks. He began in April by putting these organisms into a 1% 

 NaCl solution, and, continuing to add salt slowly, by September many 

 of these withstood a 4% solution, a solution which kills animals sud- 

 denly subjected to it. He performed the reverse experiment upon 

 marine mollusca, bringing them to live in fresh water by gradually 

 diluting the medium. According to MacDougal, 9 Lopriori found that 

 while the streaming movements of protoplasm were inhibited by 

 exposure to an atmosphere of one part oxygen and four parts carbon 

 dioxide, yet if the plant were first exposed to a mixture of 25 parts 

 of oxygen and 75 of carbon dioxide for a time, it might then be brought 

 successively into atmospheres containing 80, 85, 90, 95 and even 100 

 parts of the gas without immediate injury. Organisms can be accli- 

 matized to extreme temperatures. Davenport (loc.cit., 249) cites illus- 

 trations of both. Few active organisms can withstand a temperature 

 of over 45° C, and for whole groups like Ccelenterata, marine mollusca, 

 Crustacea and fishes 40° is a point of death. There are plant and ani- 

 mal organisms that cany on their life processes in hot springs. Simple 

 plants like Chroococcus, Nostoc, Anabcena, Leptothrix, Oscillaria, etc., 



s Davenport, C. B.: Experimental Morphology, p. 28, 

 9 Textbook of Plant Physiology, 57. 



