310 EDWARD C. DAY 
will later be referred to in connection with the sensitivity of the 
animals to light. 
The procedure of experimentation was first to study the 
activities of the normal, undisturbed animal under as natural 
conditions as possible; second, to record its reactions to stimu- 
lations of various kinds, and, third, to discover the effect of 
various operative procedures such as incisions, amputations of 
siphons, and extirpation of the ganglion, upon the sensory 
reactions and the beat of the heart. Studies made upon the 
heart-beat will be given in a subsequent paper. 
TACTILE REACTIONS OF NORMAL ACIDIA MENTULA 
A. Observations on unstimulated individuals' 
By the term unstimulated is meant cases in which I introduced 
no stimulating agent myself, although the animals were never 
entirely free from disturbing influences. 
The animals remain motionless for long intervals with both 
siphons Wide open when they are in their natural environment of 
shore-water. I have observed the same thing in the case of 
animals attached to the walls of large cement tanks in the 
Naples Aquarium, where natural conditions have been dupli- 
cated as nearly as possible. In the laboratory, although the 
tanks were large and provided with running sea-water, the 
animals in them were not entirely insulated from disturbing, 
Vibrations in the room. 
A protocol was kept of continuous observations on two speci- 
mens of Ascidia mentula for a period of about two hours and the 
time recorded for every closure of both incurrent and excurrent 
siphons. The animals were kept singly in large glass jars 
furnished with running sea-water. Both animals were very re- 
sponsive to Vibratory disturbances and closed their siphons 
whenever a door shut or somebody walked across the floor. 
Hecht ('18) finds Ascidia atra also extremely sensitive to Vibra- 
tions in the room. The response consisted simply of a puckering 
of the marginal lobes of the siphons; seldom did the Whole body 
contract. When the room was quiet for a length of time, for one 
