DEPARTMENT OF MARINE BIOLOGY. 203 



subjected. The separate half disks were put mto jars containing 1,000 c.c. 

 of sea- water and the amount of CO2 given off by the disks during any given time 

 was determined by means of a method perfected by Dr. Tashiro. 



A record of the number of pulsations per minute was made for each of the 

 disks. A count for each disk was made once each hour during the course of any 

 experiment. While there were wide differences in the rate of both the half disks 

 with sense-organs and especially in the rates of those in which a circuit wave of 

 contraction was maintained, the latter half disks always contracted at a higher 

 rate, which varied in different experiments from 1.10 to 6 times the rate of 

 the corresponding half disk on which the sense-organs were retained. As 

 the concentration of the CO2 in the closed vessels increases the pulsation-rate 

 at first rises slightly and then progressively declines until after a sufficiently 

 long period of time the toxic effects of the gas would cause the complete quies- 

 cence of the disks. These effects of the increasing concentration of the CO2 

 were much more quickly shown, and the decline in rate of pulsation was more 

 rapid for the half disks with sense-organs than for the activated disks of any 

 pair. The general average rate of pulsation for all of the experiments through- 

 out their course was for the half disks with sense-organs 26.53 per minute, for 

 the activated half disk 84.70 per minute; a proportion of 1 to 3.143. 



In spite of this marked difference in the amount of muscular activity in 

 any given period of time, the metabolism, as measured by CO2 production, 

 was with one exception actually greater from the half disk upon which the 

 sense-organs remained than for the activated member of the same pair of 

 disks, the two halves of what was originally an entire disk. In the single 

 exception to this rule the activated half disk produced a slightly greater amount 

 of COo than the one with its sense-organs intact, but the difference was exceed- 

 ingly small in proportion to the difference in the amount of muscular energy 

 expended by the two half disks during the course of the experiment. 



The Relation Between the Area of Tissue Enervated by a Single Sense-Organ 

 AND THE Rate of Pulsation in Cassiopea. 



Eimer^ observed that there was a decrease in the rate of pulsation of a medusa 

 disk the smaller the amount of tissue that was enervated by a single sense- 

 organ. He stated that the rate of pulsation declined in direct proportion to 

 the area of tissue controlled by the sense-organ. Romanes'^ pointed out that 

 the decline in rate was not directly proportional to the area of tissue, but did 

 not accurately determine the relation between area and rate. Mayer^ con- 

 firmed Romanes's observation that the decline in rate is not directly propor- 

 tional to the area enervated, but again did not determine the curve for the 

 decrease in rate. 



The records for 140 medusa disks, each with a single sense-organ remaining 

 to control the pulsation-rate, showed that when the area under the control of 

 the sense-organ was respectively the entire disk, ^, j, |, and yV of the original 

 area, there is a fairly constant decline in the rate of pulsation from 35.55 

 for the entire disk to 16.75 when only one-sixteenth of the original area is 

 under the control of the sense-organ. The complete record of the average 

 number of pulsations for each area is given below, but no attempt at an analy- 



'Eimer, Th., 1874, Ueber kiinstliche Theilbarkeit von Aurelia aurita, etc., Verhandl. physik.- 

 Med. Gesellschaft Wurzburg, N. F., Bd. 6. 



^Romanes, G. J., 1895, Jelly-fish, star fish, and sea urchins, etc., International Scientific Series, 

 vol. 49, New York. 



^Mayer, A. G., 1906, Rhjthmical pulsation in scyphomedusse, Carnegie Inst. Wash. Pub. 

 No. 47. 1906, pp. 9-10. 



