No. 4-] AMPHITHOE LONG I MAN A SMITH. 173 



Ordinarily Amphithoc lies in its nest, with the antennae pro- 

 truding from the opening at the end. The lower pair of 

 antennae are generally held motionless. The upper pair, how- 

 ever, are usually seen to be moving to and fro, sweeping about 

 in almost every direction. Occasionally their motion is sud- 

 denly checked and they are held motionless for a time, but 

 soon their moveme/it is resumed. The significance of these 

 movements will be discussed in a later section. The two pairs 

 of gnathopods are used for a variety of purposes. Occasion- 

 ally the antennae are bent downward and seized by the gnath- 

 opods and the flagella drawn through the space between the 

 dactyl and the palm. The function of this act is probably to 

 strip off any foreign bodies that may become attached to the 

 antennae. The gnathopods are frequently employed to grab 

 passing objects and to reach out and pull in bits of seaweed for 

 the construction of the nest. They are used also for holding 

 the food that the animal is eating and for carrying bits of food 

 to the mouth, where they are taken by the maxillipeds. While 

 not exercising any of their normal functions they may often be 

 seen going through the motions of grasping, with nothing to 

 grasp. This restless activity of the gnathopods seems to be 

 nothing but the exercise of the grasping reflex called forth by 

 some unknown stimulus and having no useful result. The act is 

 performed in all degrees of completeness, from a definite grasp- 

 ing motion to a mere nervous twitch. The mouth parts per- 

 form many motions when the animal is not masticating food. 

 These movements, which resemble the normal motions of 

 mastication so far as could be observed, apparently have no 

 functional significance. They take place in specimens kept 

 for a considerable time in dishes in which there is nothing 

 that could serve for food. Like the grasping actions, they are 

 movements which are called forth without the normal exciting 

 cause. 



One of the most curious actions which Amphithoe performs 

 is its reversal of position in the nest. If the antennae be 

 somewhat roughly struck with a needle, or even if a threatening 

 object suddenly appears close in front, the head and antennae 

 will appear at the other end of the nest. As the nest is a tube 



