PARKER— PHOSPHORESCENCE OF RENILLA. 175 



they depend is probably nervous. Certainly these rates are in 

 strong contrast with the rates of transmission of certain peristaltic 

 movements that are known to pass over the peduncle and the disc of 

 Renilla. These travel 0.15 centimeters to 0.12 centimeters per sec- 

 ond, one fiftieth to one sixtieth as fast as the other waves do, and 

 are very probably muscular in origin. Hence, the conclusions that 

 the withdrawal of zooids and the phosphorescence of Renilla are 

 controlled by a single form of transmission and that this transmis- 

 sion is neurogenic rather than myogenic in origin. 



If the transmission by which the phosphorescent waves of Renilla 

 are produced is nervous in character, it ought to vary with the tem- 

 perature and such seems to be the case. Thus in one set of trials 

 the rate per second was found to be at 11° C. 4.0 centimeters, at 21° 

 C. y.y centimeters and at 31° C. 20.7 centimeters. In another set 

 it was at 15° C. 6.5 centimeters per second, at 20° C. 8.3 centimeters 

 and at 25° C. 12.2 centimeters. As is shown in the second set, an 

 increase of 10 degrees in temperature is accompanied by an approxi- 

 mate doubling of the rate, 6.5 to 12.2 centimeters per second. Much 

 the same is true of the first set except for its highest member. If in 

 this set the rate per second at 21° is taken to be y."/ centimeters, at 

 11° it ought to be half that or 3.85 centimeters which is very close 

 to the oserved rate of 4.0 centimeters per second. On the same 

 basis at 31° a rate of twice y.y centimeters or 15.4 centimeters per 

 second should be looked for but the rate actually observed was some- 

 what higher than this, namely 20.7 centimeters per second. Not- 

 withstanding this divergence, which is associated with a rather ex- 

 treme temperature, it may be stated that over the greater part of the 

 temperature range for every interval of 10 degrees the higher rate is 

 approximately twice the lower one. Although the usual interpreta- 

 tion of this condition has been more or less questioned recently, it is 

 generally assumed, in accordance with the van't Hofif law, that such 

 relations in rates are indicative of chemical rather than of physical 

 processes, an assumption that would aline the kind of transmission 

 that occurs in the phosphorescent wave of Renilla with the burning 

 of a trail of gunpowder rather than with some form of transmission 

 of a purely physical type. 



