PHYSIOLOGY OF SYNAPTULA HYDRIFORMIS 351 



when once attached they remain so until fairly torn away by the 

 attachment and contraction of other tentacles. The same reac- 

 tion may also be concerned in food taking. One can readily see 

 the value of this movement should an edible particle come in 

 contact with the tentacle, since further movement toward the 

 object would more surely bring the morsel into contact with the 

 adhesive secretion on the outer surface of the tentacle, whereby a 

 subsequent wiping motion might deliver it to the mouth. 



In the reaction to the stimulus applied to the inner surface of 

 the tentacle there is possibly another adaptive movement. The 

 waving of the tentacle after its contact with an edible particle is 

 likely to bring the outer adhesive portion into contact with the 

 object, which might thus be captured and carried to the mouth. 



All other reactions are clearly negative, varying in degree of 

 completeness with the strength of the stimulus. 



It seems very probable that the touch papillae do have the 

 function of 'tangoreceptors,' but whether they are exclusively 

 such is debatable. Their distribution corresponds with the order 

 of sensitivity, since they are especially abundant on the tentacles 

 and appear to be less numerous on the mid-body than on the 

 posterior end. 



Water currents directed on various parts of the body gave 

 results such as those shown in table 3. The method of making 

 the tests was as follows. A pipette bent at right angles was 

 held in a vertical position with its horizontal outlet at a level 

 with the portion of the body to be tested. Water having been 

 drawn up into the pipette to a given height and held there by 

 keeping the finger over the upper opening, the lower end of the 

 pipette was then placed about 2 mm. from the region of the body 

 to be stimulated and the finger suddenly lifted from the pipette. 

 In this way practical uniformity in the strength of the stimuli 

 was secured. 



Individuals varied greatly in their responses to water currents. 

 In general, a current from a column 4 cm. high produced no ef- 

 fect on the tentacles or head end. On the mid-body it caused 

 shortening of the body, and on the posterior end shortening of 

 the body with local contractions in addition. A slightly stronger 



