PARKER— PHOSPHORESCENCE OF RENILLA. 173 



suits in what seems to be a series of luminous waves that emanate 

 concentrically from the region of stimulation. When one of these 

 wave fronts is closely scrutinized, it is found to be not a continuous 

 line but a series of luminous points which represent the small masses 

 of white material already alluded to and which for the moment lie 

 in what would be a continuous w^ave front. Thus the appearance 

 of a luminous wave is due to the momentary glowing of one concen- 

 tric ling of points after another as the impulse that induces the phos- 

 phorescence spreads from the center of stimulation outward. 



When the disc of Renilla is cut into and the animal is subse- 

 quently excited to phosphoresce, the luminous waves pass round the 

 incisions without interruption so long as organic continuity is pres- 

 ent. If the disc is cut nearly in two transversely, the waves of 

 phosphorescence can be started in either piece and will pass thence 

 over the connecting bridge to the other place. If the disc is cut into 

 a scroll that can be unfolded into an elongated form, stimulation 

 at one end will start a luminous wave that will pass to the other. 



If a Renilla is split longitudinally through its chief axis, the two 

 halves remaining attached only through the distal part of the pe- 

 duncle, the stimulation of one half calls forth a flash of light in that 

 half which, after it has subsided, is followed by another flash in the 

 other half. The second flash follows the first at such an appreciable 

 interval of time that the preparation seems to wink first w^ith one 

 eye and then with the other. Here the interval between flashes is 

 due to the transmission of the wave of excitation through the non- 

 luminous peduncle, for if the peduncle is completely split no such 

 transmission occurs even if the two halves are closely applied to 

 each other. This observation shows that the luminous waves are 

 under the control of some form of transmission, non-luminous in 

 character, that spreads in wave-like fashion and for which the phos- 

 phorescent waves may be said to be luminous replicas. It also 

 makes clear that the peduncle can transmit the impulses that excite 

 luminosity in other parts. Not only can be peduncle transmit these 

 impulses, but it can also originate them, for if the tip of the pe- 

 duncle of Renilla is pinched, after a moment the disc flashes in 

 waves of phosphorescence. 



As might be inferi-ed, any portion of the disc carrying the white 



