DEPARTMENT OF MARINE BIOLOGY. 199 



C. The Influence of the Sense-Organs on the Total Metabolism, as Measured by 

 CO2 Production in Cassiopea. 



Continuing the experiments started last season in collaboration with 

 Dr. S. Tashiro/ a series of determinations was made of the total amount of 

 CO2 produced by the separate halves of a medusa disk, one of which was 

 pulsating under the influence of its sense-organs, while the other was acti- 

 vated in the manner previously described for regenerations and starvation 

 experiments. The comparison of the halves of 50 disks was made in this 

 manner, with results which confirm those previously obtained, namely, that 

 the half-disk pulsating more slowly under the influence of its sense-organs 

 produces as much CO2 as the more rapidly pulsating activated half. 



As pointed out on pages 195-196, the rate of pulsation is a true measure of 

 muscular work done when a labyrinth of subumbrella tissue has been formed 

 on each of the half-disks. The results of this series of experiments, there- 

 fore, are completely in accord with those obtained from experiments dealing 

 with the influence of the sense-organs upon the rate of regeneration and the 

 loss of weight during starvation. 



As the greater number of these experiments were allowed to continue 

 until one of the half-disks of a pair has ceased to pulsate under the narcotiz- 

 ing effects of the CO2, it was possible to secure a measure of the CO2 concen- 

 tration necessary to bring about narcosis. In nearly all instances the 

 activated half-disk was the first to succumb, and once it had stopped it could 

 not start pulsating again until stimulated by an induction shock. The 

 half-disks with sense-organs shov/ed more resistance to CO2, and when 

 removed from the closed jars Avhere they had ceased to pulsate and put into 

 fresh sea-water, they would start pulsating again within 1 to 2 minutes, 

 even when they had been inactive for several hours. 



Throughout these experiments the records of CO2 production were made 

 in terms of increased hydrogen-ion concentration of the sea-water in the 

 closed jars, and up to the time this report was written not all the necessary 

 data had been secured to complete a curve to show the amount of CO2 

 necessary to bring about a given change in the hydrogen-ion concentration 

 of the unit volume (1,250 c.c.) of sea-water used in the experiments. This 

 phase of the work is being completed at the Biological Laboratory at Prince- 

 ton University. 



D. The Changes in the Rate of Nerve-Conduction in Cassiopea in Response to 



Change in Temperature. 



The experiments upon this subject were undertaken primarily to determine 

 the response of the sense-organs to changes in temperature. Mayer^ has 

 shown that the initiation within the sense-organs of the stimulus for normal 

 pulsation is a relatively simple chemical reaction. It was therefore thought 

 possible that if a single sense-organ with only a narrow band of tissue con- 

 necting it to the remainder of the disk was subjected to changes in tempera- 

 ture, while the remainder of the disk was kept at a constant temperature, 

 the change in the rate of pulsation might follow Van't Hoff's law more closely 

 than other measurable biological processes have been found to do. It was 

 ascertained, however, that even in water of constant temperature the rate of 

 pulsation of a disk ennervated by a single sense-organ varied too widely 

 within the tune covered by one of these experiments to give any conclusive 

 results. 



^Year Book No. 14, Carnegie Institution of Washington. 



^Mayer, A. G., on Rhythmical Pulsation in Scyphomedusa, Carnegie Inst. Wash. Pub. No. 102. 



