94 



due to the pressure of blood that is producing the reappearance of 

 the subradular organ. With the exposure of the latter structure the 

 series of events just described is again inaugurated. 



Fig. A — D. Slightly diagrammatic figures illustrating movements (in direction of 

 arrows) of the subradular organ (s) and radula of Cryptochiton Stelle ri. Natural 

 size from living specimen. 



Essentially these same movements occur when the animal is feed- 

 ing. When a piece of irregular and comparatively firm alga is being 

 drawn into the mouth it is possible to see the subradular organ pressed 

 against the food (never under such circumstances is it protruded from 

 the mouth) and after its withdrawal and the backward movement of 

 the lingual ribbon have ensued to see the plant drawn inward by the 

 interlocking teeth (Fig. C). Every bite of food, before it is carried in 

 by the radula, is thus tested by the subradular organ which, so far 

 as we can judge, functions as an organ of taste. 



As was mentioned earlier in the account the subradular organ in 

 Cryptochiton is not protruded from the mouth except in the case 

 of animals starved at least five or six days and often longer. Further- 

 more it is then never projected except in connection with the complex 

 series of movements attendant upon the usual taking of food and I 

 am strongly of the opinion that where food is not present it is an 

 unnatural process. On the other hand I have many times slipped 

 splinters of wood or decayed pieces of certain algae under the animal 



