156 



Papers frofn the Department of Marine Biology. 



involve the activities of distinct tissues, the influence of the sense- 

 organs is exerted in a manner strikingly similar in the two cases. This 

 similarity in result suggests the probability that the effects measured 

 are only different phases of 

 the general metaboUc activity 

 of the organism, which when 

 measured as a whole would 

 show an influence of the nerve- 

 centers comparable to that 

 obtained when the activities 

 involved in distinct functions 

 are used as the unit of meas- ^ 

 urement. '^ 



The measurement of the -^ 

 amount of carbon dioxide ^ 

 given off by a half-disk within Z 

 a given space of time affords ^ 

 means of determining the 

 comparative rate of total 

 metabolic activity of speci- 

 mens under the operative 

 conditions used in the previ- 

 ous experiments. The tech- 

 nique of the experiments was 

 as follows: The half-disks fio. 

 were prepared in the manner 

 previously described, so that 

 active, activated, and inac- 

 tive individuals were secured 

 for comparison. Each half-disk of any pair was placed in a separate 

 jar containing about 1,200 c.c. of fresh sea-water brought from the 

 ocean at the time of beginning a set of experunents. The capacity of 

 the jars varied slightly and pairs of equal volume had to be selected for 

 the two halves of the same disk. 



As the measurable amount of CO2 produced and consequently the 

 rate of pulsation for some time after the beginning of an experiment 

 were largely dependent upon the activity of the zooxanthellse, most of 

 the experiments were started late in the afternoon and therefore 

 continued during the hours of darkness. When experiments were 

 going on during the day the necessity for covering the jars with dark 

 cloth caused a decided rise in temperature, which increased unneces- 

 sarily the complication of the calculations involved in determining the 

 amount of CO2 given off in respiration. 



Preliminary experiments along this line were undertaken, in collabo- 

 ration with Dr. S. Tashiro, in 1915, when the determinations were 



23 25 27 29 31 



33 35 37 39 



13. — Showing efifect on rate of pulsation of 

 active and activated halves of the same medusa 

 disk when subjected to an increase in tempera- 

 ture from 23° to 40° C. The upper curve is for 

 the activated specimen ; the lower curve for the 

 active specimen. 



