234 Journal of Comparative Neurology. 



body is turned to one side (Carcinus, Astacus, Pachytylus, 

 Apis, Dytiscus). The lowering of the muscular tone is, how- 

 ever, perhaps plainest to be seen in the case of those animals, 

 in which the body-segments are movable against each other. 

 Here is always to be seen a curvature of the body toward the 

 uninjured side, when the operation is made on one side only 

 (Astacus, Squilla, Apis). From this and from the fact that 

 only the extremities of the operated side of the body are held 

 abnormally after section of an oesophageal commissure, it fol- 

 lows that each half of the brain exercises a tone only or chiefly 

 upon the same side of the body. 



The above conclusion is hinted at from the changes of 

 tone in the organs which are innervated by the brain. For ex- 

 ample there is observed a change in the position of the eyes of 

 Carcinus, Astacus, and Squilla ; of the first pair of antennae in 

 Carcinus, of the second pair of antenuEe in Astacus and Squilla 

 and the antennae in Hydrophilus. This change in tone is par- 

 ticularly well shown through the asymmetry which arises after 

 section of one of the oesophageal commissures and extends 

 here chiefly to the organs innervated by that half of the brain 

 situated on the same side. Is it to be concluded from this, 

 that the ventral cord exercises a tone upon the parts of the 

 body situated in front in the same way as the brain does on the 

 parts of the body situated more posteriorly ? At most, only 

 the suboesophageal ganglia could be considered since after sec- 

 tion of the commissures behind this ganglionic mass a change 

 in the tone of the organs of the head no longer takes place, 

 and, further, changes of the front part of the animal (in front 

 of the section of the ventral cord) after cross-section of the 

 ventral cord can under no conditions be confirmed. 



It has been claimed that Arthropods after removal of the 

 brain cease to make spontaneous movements. If we are to 

 understand by spontaneous motions that an external stimulus 

 is not evident for the origin of the motion or for the change of 

 one form of motion to another, then spontaneity is present in 

 all of the Arthropods observed by me after removal of the 

 brain. It was best demonstrated in the case of Astacus, where 



