1916.] NATURAL SCIENCES OF PHILADELPHIA. 85 



April 18. 

 The President, Samuel G. Dixon, M.D., LL.D., in the Chair. 



Thirty-five persons present. 



The deaths of the following members were announced: 



Emlen Physick, March 21, 1916. 

 Charles Chauncey, April 3, 1916. 

 Norton Downs, April 15, 1916. 



The Publication Committee announced the presentation of a 

 paper entitled ' ' Contributions to the Anatomy of Python reticulatus 

 (Schneider)," by Joseph C. Thompson (April 8, 1916). 



Temperature and the Activities of Animals. — Merkel H. Jacobs, 

 Ph.D., remarked that the continued existence of living organisms 

 is possible within a range of temperature of the order of magnitude 

 of possibly one one-thousandth of that encountered in the universe. 

 The majority of the activities of organisms occur within the region 

 from slightly below 0° C. to about 45° C. For individual species the 

 range is usually less — sometimes as little as 15° or even 6° C. A 

 certain number of forms can exist for a short time in a more or less 

 inactive condition through a range of 350° C. or more. 



Even within the natural range for a species the effects of different 

 temperatures is very striking. A rise of 40° C. may cause at least 

 a 16-fold increase in the rate of most of the chemical reactions under- 

 lying the various manifestations of life. Since different processes 

 are accelerated unequally by such a rise and since the point of equi- 

 librium in reversible reactions is changed, the effect on the organism 

 a- a whole may be qualitative as well as quantitative. The use of 

 high temperatures has been a favorable means of securing striking- 

 modifications of existing forms of life. A possible case of a heritable 

 variation produced in this way is the three-vacuoled race of Parame- 

 cium which appeared sixteen months ago in the Zoological Laboratory 

 of the University of Pennsylvania and which has remained constant 

 ever since. 



Different organisms are differently situated with respect to the 

 daily and yearly changes of temperature they are called upon to 

 meet. Many marine forms are subject to an average change of less 

 than 1° C. a day and 2° or 3° a year. On the other hand, terrestrial 

 forms and those living in small bodies of fresh water frequently 

 endure a daily range of 30° C. or more. The rotifer Philodina roseola 

 is subjected to especially severe conditions. Living in small pools 

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