496 G. H. PARKER 
ments, quadrants, centers, margins, or even minute fragments 
will on appropriate treatment give out light. 
The impulses that induce phosphorescence are profoundly 
influenced by such anesthetics as magnesium sulphate. If a 
portion of the rachis of a Renilla is covered with crystals of mag- 
nesium sulphate, waves of luminosity can be started in the un- 
treated part and will pass into the treated part for about four or 
five minutes, after which they will cease on the edge of the treated 
part, nor will this part give out light even when it is directly 
stimulated. . On washing off such a preparation and putting it 
in pure sea-water, the power to produce light will return to the 
treated part in half an hour or so. If a preparation is made by 
cutting a rachis almost in two by a transverse incision and, after 
determining that the connective bridge will transmit luminous 
waves, this bridge is covered with crystals of magnesium sul- 
phate (as in fig. 7), the waves of light will in ten minutes or so 
be blocked at this point and light will be produced in only that 
part of the rachis which is directly stimulated. If the edge of 
a rachis is cut off in the form of a strip 5 to 6 mm. wide and this 
strip is pinned out in sea-water, waves of phosphorescence can 
be made to run over it in either direction by appropriate stimu- 
lation. If, now, crystals of magnesium sulphate are freely. 
applied to the middle of the strip, the luminosity of the region 
thus treated begins to decline and, after five minutes, it ceases 
altogether, though occasional waves that seem to stop on one 
side of it reappear on the other side. A complete block occurs, 
however, in from nine to ten minutes and waves of phosphores- 
cence started on one side of the treated area do not reappear on 
the other. After half an hour in pure sea-water the phosphor- 
escent waves reestablish themselves and pass freely through the 
region previously anesthetized with magnesium sulphate. 
If a V-shaped preparation is made from a Renilla by splitting 
it through its long axis except at the distal end of the peduncle, 
it will be found, as already stated, to transmit impulses for light 
production from one half-rachis to the other through the partly 
split peduncle. If the unsplit portion of this part is covered with 
crystals of magnesium sulphate, in five to ten minutes no impulses 
