146 PROCEEDINGS OF THE ACADEMY OF [March, 



That is, the Ontogeny of the individual springs from its Heredity, 

 with its incessant reactions and origins, in response to its Environ- 

 ment. 



Similarly, Heredity is sooner or later in the history of a phylum 

 under the influence of the three factors, Ontogeny, Environment, 

 Selection, as represented in diagram B. 



This conception of the continuous interoperation of the four 

 factors in no way diminishes Heredity as the final seat of all genetic 

 change; either from the first or as a sequel to a long series of ante- 

 cedent interoperations, the seat of the origins and of the transforma- 

 tions of characters is certainly in Heredity. 



Thus so far as the present law is concerned, the problem of evolu- 

 tion is to determine the relation between the interoperation of the 

 four factors E, 0, H, S, and the final fixation of the results of this 

 operation in Heredity. 



Merkel H. Jacobs, Ph.D. : " Physiological Characters of Species." 



In the experiments, on which the paper was based, an attempt 

 was made to compare a number of organisms with regard to certain 

 of their physiological characters. The organisms selected were 

 twelve species of protozoa, viz., Paramecium caudatum, P. aurelia, 

 P. bursaria, Colpidium colpoda, Coleps hirtus, Blepharisma lateritia, 

 Euplotes patella, Vorticella nebulifera, Peranema trichophorum, 

 Euglena viridis, Chilomonas Paramecium, and Entosiphon sulcatum. 

 The character chiefly studied was the effect of carbon dioxide on the 

 movements and the general vitality of these forms. 



The experiments showed that each of the species in question 

 reacts to carbon dioxide in a characteristic manner and that each 

 has a general resistance to its toxic effects, which while varying to 

 some extent with different individuals and in different cultures, is 

 nevertheless fairly constant for the species. The most sensitive 

 form studied was found to be Coleps hirtus, which is killed, as a rule, 

 in three or four minutes, while Colpidium colpoda, the most resistant 

 form, under exactly the same conditions, remains uninjured after 

 many hours. Some forms were killed outright very quickly, while 

 others, although losing all power of movement within a few moments, 

 yet retained for a long time the ability to recover when again re- 

 stored to normal conditions. 



One of the most striking results obtained was the demonstration 

 of the difference in the effects of carbon dioxide on different elements 

 within same cell. In general, contractile structures (myonemes) 

 are paralyzed within a few seconds, while vibratile structures (cilia, 



