EXPERIMENTS ON ARTHROPODS 105 



appendages retained their function, and eating move- 

 ments were performed reflexly when meat was placed 

 on the appendages. The rest of the appendages 

 were entirely paralysed, with the exception of the 

 gills on the ventral side of the abdomen. The animal 

 was reduced to a mere eating and breathing machine. 

 It was fed artificially and so kept alive. 



Patten has shown further that each feeding-appen- 

 dage continues to take food normally and carries it 

 to the mouth if the piece of the cesophagus-ring 

 from which its nerves take their origin is preserved. 

 These feeding-appendages discriminate the chemical 

 and tactile nature of the food that is offered them, 

 just as the tentacles of the Actinians do they refuse 

 to accept it unless the substances offered fulfil cer- 

 tain chemical and mechanical conditions. As regards 

 the conception of these phenomena and their mechan- 

 ics, no difference, of course, exists between the be- 

 haviour of the tentacles of the Actinians and the 

 behaviour of the mouth-appendages of the Limuli ex- 

 cept that determined by the skeletal relations. 



If we remove one half (for instance, the right half) 

 of the supracesophageal ganglion in Limulus (0, Fig. 

 31), the animal usually moves no longer straight 

 ahead, but in a circle with more or less of a curvature 

 toward the uninjured (left) side. This is an instance 

 of the well-known circus-motions. We shall return 

 to the mechanics of such motions in a later chapter. 



If the whole supracesophageal ganglion be re- 

 moved, the animal is able to take food placed upon 



