130 REPORTS Olf INVESTIGATIONS AND PROJECTS. 



This jellyfish is quite sensitive to shocks and to slight changes in tempera- 

 ture, so that an accurate temperature-pulsation curve could not be plotted. 

 Enough data were obtained to show that the pulsation-rate follows a chemical 

 temperature coefficient (about 3 for 15° to 25° and 2 for 20° to 30°). This 

 was to be expected, as other rhythmical tissues have been shown to behave 

 similarly. 



In 1906 Mayer* discovered that a ring-shaped piece of tissue could be so 

 stimulated as to entrap a conduction wave which travels around the ring in 

 one direction, stimulating the muscles as it goes. The rate at which this 

 travels is so regular that it offers a favorable object for the study of nerve- 

 conduction at different temperatures. It is difficult to start a wave at low 

 temperatures, but a curve between 18° and 38° was obtained. It is a right 

 line to 29°, then a gradual falling off to a maximum velocity of propagation 

 at 33°, and then a diminution of rate with increasing rise of temperature. 

 The increase in rate for 10° indicates a chemical change as the basis of 

 conduction. 



The effect of solutions which stop contraction and conduction was tried at 

 different temperatures 10° apart to determine if the solutions acted in a 

 chemical way (as formation of ion-proteids) or in a physical way (as change 

 in surface tension). Owing to the difficulty of obtaining and keeping ice at 

 Tortugas, only a limited number of experiments could be performed. 



Temperatures of 24° to 34° were used in order to have the conditions as 

 near normal as possible, and % m MgClg was tried first. At 34° the power 

 of contraction and conduction was stopped about 2 to 2.5 times as soon as at 

 24°. This indicates a combination of Mg with some muscle constituent, per- 

 haps an Mg-proteid, and that the reaction velocity of this particular reaction 

 has a temperature coefficient of about 2.5. The reverse experiment gave a 

 very peculiar result. The strips of tissue were first placed in ^ w MgClj at 

 29° for a certain time, then removed to sea-water at 24° and 34°. The nerves 

 always recovered instantly (< one-half minute), the muscles in times which 

 indicate only a partial chemical temperature coefficient for one set of muscles. 

 This can only be made clear by actual data which will be given in the com- 

 plete paper. Here, then, is apparently a reversible process which proceeds 

 in one direction with a chemical temperature coefficient, while in the reverse 

 direction it is instantaneous (in the case of nerve-conduction), slow, but not 

 following definitely a chemical temperature coefficient (in the case of muscle 

 contraction). 



A few experiments, with 20° to 30° as the 10° interval, gave quite differ- 

 ent results. Contraction was stopped at about the same time in the two 

 solutions, in some cases sooner, at 20°. Experiments in sea-water at 34° and 

 22° showed that contraction is not so vigorous as at 34°, and I am inclined to 

 believe that this might so lessen the time of activity in MgClg at 20° as to 

 mask the chemical temperature coefficient. In other words, we are dealing 

 with a double effect. 



Similar experiments with CH3COOH gave essentially similar results. 

 Experiments with chloroform sea-water gave rather indefinite results. I 

 hope to continue these experiments on other tissues, perhaps more favorable 

 for temperature experiments than those of tropical animals. 



* Carnegie Institution of Washington Publication 47, 1906. 



