324 RESEARCH SEMINAR. 



main facts presented were as follows : The adult ring dove has 

 only three principal calls, but these have a number of modifica- 

 tions, which, together with many expressive movements, afford a 

 considerable variety of expression. All these modes of behavior 

 seem to be strictly inherited. They develop in the young bird 

 very gradually, and in a definite order which is probably also the 

 order of their development in the race. 



August 2+. Some Reactions of Mnemiopsis Leydyi (A. Ag.). 



By GEORGE WILLIAM HUNTER, Jr. 



Mnemiopsis orients itself with reference to gravity, being nega- 

 tively or positively geotropic under differing conditions. It has 

 two characteristic resting positions, one at the bottom with the 

 aboral pole upward and one at the surface of the water with the 

 oral pole upward. 



In strong and moderate intensities of light it may be first 

 negatively and later positively photopathic ; to very weak inten- 

 sity of light it may be positively photopathic. Some evidences 

 of phototaxis are found under strong light, the aboral end being 

 directed toward the light. 



The animal reacts toward a moderately strong constant cur- 

 rent (one half to three volts) by turning the aboral pole toward 

 the anode and moving to the cathode. A weaker current may 

 cause orientation without movement toward the cathode. 



The action of the "make" and "break" upon muscles and 

 cilia depends upon the position of the electrodes and the strength 

 of the current. 



Mnemiopsis is relatively more resistant to decrease than to 

 increase in the temperature of the water. Responses to electrical 

 stimulation under conditions of greater heat than normal show 

 decrease in reaction time up to about 29 C., then rapid increase in 

 reaction time. Responses to electrical stimulation under condi- 

 tions of decrease from normal temperature show little change in 

 reaction time to about 15 C., then a slow increase in reaction time. 



August 24. The Reaction Time of Gonionemus Murbachii to 

 Electric and Photic Stimuli. By ROBERT MEARNS YERKES. 

 This experimental study of the time relations of the neural 



processes of Gonionemus indicates : (i) A reaction time to elec- 



