216 W. J. CROZIER 



It is clear, then, that light exercises a distinctly inhibitory 

 effect on light production by these enteropneusta. Small frag- 

 ments of the balanoglossids will, if kept in darkness, respond at 

 night to a blow struck on the side 'of their container, by the 

 emission of a bright glow. But even these isolated pieces are 

 affected by bright light just as are the complete animals. Hence 

 a central nervous effect is eliminated, and it is legitimate to 

 state that light can act directly on Ptychodera (and Glosso- 

 balanus) in such a way as to inhibit the excretion of light-pro- 

 ducing substances. I was unable to carry out an experiment 

 which would submit one portion of a Ptychodera to light while 

 the rest remained in darkness, and can therefore say nothing 

 about the possible nervous transmission of this kind of photic 

 influence. 



SUMMARY 



Balanoglossids are here described which are photokinetic, 

 and orient away from the light in a machine-like manner. In 

 addition to the orienting stimulus, it is shown that light has 

 another, possibly separate, effect upon these animals, namely 

 the inhibition oL light production. The tip of the proboscis 

 is the part mo£t sensitive to illumination, but the rest of the 

 animal's surface is likewise open to stimulation by light. The 

 collar nervous system (delaminated part) is unnecessary for the 

 coordinate^Unovements of orientation, and also for the inhibitory 

 influence of light on the production of luminescence. 



