On the Nervous System of Cassiopea Xamachana. 167 



of a will differ under different experimental conditions, but all observed 

 instances agree closely with the expectations. 



(9) The greater part of the loss in weight appears to be shown by 

 the mesogloea, which undergoes marked histological changes during the 

 course of starvation. 



(10) As in regeneration experiments, the greatest metabolic activity 

 is shown by the active specimens, the least by the inactive, while the 

 activated individuals stand in an intermediate position, being closest 

 to the one in which muscular activity is entirely suppressed. (Table 

 9, and figures 10, 11, and 12.) 



(11) Specimens as prepared for the previous experiments were kept 

 for various periods in closed jars of sea-water, each containing about 

 1 ,200 c.c. The amount of CO2 given off was ascertained by determining 

 the hydrogen ion concentration of this water at the beginning and end 

 of each experiment. The volume of CO2 necessary to bring about the 

 observed change was determined by adding known volumes of this gas 

 to 1,200 c.c. of sea-water, as shown in figure 13. 



(12) While the rate of pulsation of the activated half -disks was gen- 

 erally more than 3 times that of the active half of the same disk, the 

 amount of CO2 given off in respiration from the activated specimen 

 was never more, and almost always considerably less, than that from 

 the active specimens of any pair of half-disks. In general the results 

 from this type of experiment are in perfect accord with those obtained 

 from those recorded in sections I and II, where the standard of measure- 

 ment was a component part of that used in the respiration experiments. 



(13) The change in rate of nerve-conduction (pulsation) in activated 

 specimens over a range in temperature from 23° to 33° C. follows nearly 

 a straight line, the actual rate being approximately doubled for this 

 increase of 10° C. Beyond 35° the rate rapidly declines, death ensuing 

 at 38°. The curve for this change resembles very strikingly that for 

 enzyme action. The change in rate of active half-disks is much more 

 erratic. Such specimens can, however, be carried to much lower 

 temperatures (14° C.) before activity ceases, and the upper hmit of 

 temperature was always higher by 2 or 3 degrees than for the activated 

 half of the same disk. When a single sense-organ was subjected to 

 changes in temperature, the remainder of the disk, without its sense- 

 organs, being maintained at a constant temperature, the results showed 

 no characteristic difference from those obtained when the whole disk 

 w^as subjected to the temperature change. 



(14) As the area of tissue enervated by a single sense-organ is succes- 

 sively reduced to one-half its former extent at each operation, the rate 

 of pulsation declines until, when the area has been reduced to ^V its 

 original extent the pulsations will have been reduced to approximately 

 half their original number. Beyond this point the reduction in rate 

 of pulsation followed the same ratio to the area, at least until the final 



