682 



EAYMOND PEAEI;. 



and its reactions observed. Evidently, so far as injury of 

 the mechanism by the operation is concerned, such a piece 

 is in essentially the same condition as the pieces described 

 in the previous expeimnent. It has only one complete side 

 of the body. The piece when inverted scpiirmed about consider- 

 ably at first, but gave no indication whatever of the normal 

 spiral reaction. In a short time the violent movements ceased, 

 and a notch was noticed in about the middle of the uncut 

 edge (cf. Fig. 40, h). This soon grew larger, and extended 

 more and more towards the ends of the piece, as shown in 



l'"iG. iO. — a. Operation diagram, ileavy lines indicate tiic cuts. 0, c, 

 and d. Successive stages in tlie righting reaction of the piece A of 

 diagram a. e and /. Cross-sections through A at two successive 

 stages in the rigliting process. See text for further explanation. 



c and d. By close observation the cause of this appearance 

 was found to be that the thin mobile edge was folding 

 under and attaching its ventral surface along the bottom. A 

 cross-section through the worm at this stage had the outline 

 shown in e. As soon as a considerable portion of the edge 

 had so folded under and become attached, the piece gave 

 a series of strong contractions and literally " flopped " over 

 the attached edge and came down right side up. A stage in 

 this process is shown in cross-section in /. This behaviour 

 was so peculiar, and at the same time precise, that the 



