406 



THE AMERICAN NATURALIST [Vol. XL 



tube caused a restless indeterminate movement of the distal ten- 

 tacles. 



No extensive experiments with light were attempted. Colonies 

 were placed in the dark and then suddenly illuminated by a 16 c. p. 

 electric light, or a shadow was cast over them after they had been 

 illuminated for some time, but no observable reactions occurred in 

 either case. It was also noted that the colonies grew just as abun- 

 dantly on the sides of the piles most exposed to light as on those 

 least exposed. 



Summary 



1. The proximal tentacles of Tuhularia crocea react to mechan- 

 ical stimulation by bending toward the manubrium. 



2. The distal tentacles react to mechanical and chemical stimu- 

 lation by bending toward or away from the mouth, and this action 

 may be accompanied by a bending of the manubrium toward the 

 stimulated side. 



3. Apparendy no part of the hydranth is sensitive to very dilute 

 solutions of meat juice, onion juice, and oil of cloves or bergamot 

 (so called "odorous" substances). 



4. The minimum temperature at which reactions occur is 0° C. 

 and the maximum about 26° C. 



5. Sudden change from strong light to shadow or from dark- 

 ness to strong light has no apparent effect upon the animals. 



