UNIVERSITY OF CALIFORNIA PUBLICATIONS 
ZOOLOGY 
Vol. 2, No. 7, pp. 333-340, Figs. 1-5 December 13, 1905 
CONTRIBUTIONS FROM THE LABORATORY 
OF THE 
MARINE BIOLOGICAL ASSOCIATION OF SAN DIEGO. 
Vit: 
THE BEHAVIOR OF CORYMORPHA. 
BY 
HARRY BEAL TORREY. 
In a former paper ( :04),1 it was shown that Corymorpha pos- 
sesses an unusually wide range of activities for a hydroid. It 
responds to mechanical and thermal stimuli, to chemieal stimuli 
that produce their effect as mechanical irritants, not as odorous 
substances, and to gravity. In the movements of the stem, it 
resembles such naked forms as Hydra, Clava and Hydractinia. 
The stem is everywhere sensitive to mechanical stimuli, bending 
from side to side or shortening under their influence. Such re- 
actions are due to the contractions of longitudinal muscle fibers 
which are situated in the usual fashion deep in the ectoderm. 
A lengthening of the stem may be caused wholly or in part by 
the circular endodermal musculature. 
The long proximal tentacles, about twenty-four in number, 
may respond singly to direct mechanical stimulation or to a 
stimulus applied either to another tentacle or a distant portion 
of the stem. In all eases of effective stimulation, direct or indi- 
rect, they bend invariably toward, never away from the mouth. 
The reaction is rapid; the recovery, which ends in the resumption 
of the expanded condition, is slow. 
The initial reaction of the distal tentacles to all effective 
stimuli is, on the other hand, always away from the mouth; 
* Biological Studies on Corymorpha. I. C. palma and Environment. 
Jour. Exp. Zoology. I, No. 3, 1904. 
