8 



Hooker: Physiological observations 



half after stimulation movement was detected, whereupon the 

 fly-leg was removed. After fifteen minutes the tentacle was well 

 bent and the gland had moved through an angle of about fifty 

 degrees. Marked elongation took place on the convex side near 

 the base in Segment 6, and to a lesser extent in Segment 5. The 

 concave side remained nearly of the same length as before. The 

 region of bending is coincident with the region of elongation on the 



Fig. I. Side views of a tentacle in the process of bending, X 22. a, before 

 stimulation; b, c and d, successive stages of inflexion; e, the fully bent tentacle. 



convex side. As the tentacle continued to bend, the area of 

 curvature and elongation was extended upward toward the gland, 

 including Segments 4, 3, and 2, and to a lesser extent downward 

 so as to include a portion of Segment 7. In the ultimate stage 

 the curved region subtended an angle of approximately 215 

 degrees. Both sides increased in length, but the increase of the 

 convex side was eight times that of the concave. Fig. i is a 

 series of camera lucida drawings made during the inflexion of this 

 tentacle. In b the bending region is seen to be restricted at first 

 to the lower end and to extend apically in c and d. The final 



