196 



CARNEGIE INSTITUTION OF WASHINGTON. 



variations were in all instances less than the unit of measurement, so that 

 any irregularities in the operations were not of sufficient magnitude to 

 appreciably affect the results of any series of experiments. 



As the influence of the rhopalia on the rate of generation is most marked 

 in the earlier stages, a number of experiments were carried out to determine 

 the effect of the removal of the rhopalia at different intervals of time after 

 the original operation. The first operation consisted of the separation of 

 each disk into halves and the removal of a disk of tissue 22 nam. in diameter 

 from near the cut edge. The halves of each disk were kept in the same 

 jar of sea-water and the rhopalia removed from one half at intervals after 

 the operation, as shown in table 2. 



Table 2. 



All these experiments were carried on until the cavity had been closed by 

 the regenerating tissue. In every instance a period of at least 24 hours 

 from the time of the first operation was necessary in order that the rates of 

 regeneration should be the same for the two halves of the disk. When the 

 rhopalia were removed, in less than 24 hours from the time of the first opera- 

 tion, it was impossible to recognize any difference from the regular type of 

 experiment in which the rhopalia were removed from one half-disk of each 

 pair at the time of the beginning of an experiment. 



In many of the experiments to determine the influence of the rhopaha on 

 the loss of weight of starving and regenerating disks, a 22 mm. disk of tissue 

 was removed from each half-disk and a record of the amount of regeneration 

 was made at the time of the daily weighing of the specimens. The opera- 

 tions in these experiments were similar to those used in previous regeneration 

 experiments and the results for regenerations were in perfect accord with those 

 previously obtained. 



B. Influence of the Rhop.\li.\ on the Loss of Weight in Regenerating Disks op 



Cassiopea. 



Mayer^ found that Avhen a complete normal Cassiopea was starved in 

 sea-water from which all food organisms had been removed by careful filtra- 

 tion the loss of weight could be expressed mathematically by the formula 

 y = W{l — a)x, in which W equals the original weight, x the number of days 

 of starvation, and a a constant, the "coefficient of negative metaboUsm." 



As would be expected, the loss of weight of the disk alone does not corre- 

 spond exactly to that for the entire medusa. The value of a in the equation 

 given above differ.s in experiments involving varying conditions as regards 

 light and darkness, presence or absence of regeneration, etc., but in all cases 

 the above foimula gives a veiy close approximation to the observed loss of 

 weight. 



^Mayer, A. G., The Law Governing the Loss of Weight in Starving Cassiopea; Publication 

 No. 183, (,'arncgio Institution of Washington. 



