134 MANTON COPELAND. 



behavior of the pedal cilia of Alectrion suggests that they have 

 in some way been appropriated by the nervous system and are 

 controlled directly or indirectly by nervous impulses. Although 

 little more than a beginning has been made in the study of this 

 phase of the problem, the results of certain experiments are 

 sufficiently important to warrant a preliminary report at this 

 time. They have been obtained for the most part from a study 

 of ciliary behavior after the foot has been removed from the rest 

 of the snail's body. 



When the somewhat contracted, excised foot of Alectrion 

 trivittata is placed in sea water and viewed under a microscope 

 the greater number of cilia are seen to be motionless. If now the 

 anterior margin of the foot is watched, it will be observed that 

 at intervals slight contractions of the border occur accompanied 

 by the beating of the anterior fringe of cilia over the area moved. 

 This muscular movement is not extensive, but consists of a 

 sudden withdrawal of a short segment of the pedal border so 

 that for a moment it appears slightly indented, the contraction 

 being immediately followed by an expansion which restores the 

 normal contour of the foot. The ciliary activity is also but a 

 momentary affair and is restricted to the contracted region. 

 The cilia usually appear to beat either synchronously with 

 the contraction or directly after it, but in certain instances 

 ciliary movement seems to precede slightly the muscular move- 

 ment. These contractions accompanied by local ciliary action 

 sometimes continue for hours. Sooner or later, however, the 

 twitching of the muscles becomes more vigorous and frequent, 

 and the cilia fail to come to rest between contractions. Some 

 of them may be beating continuously at the same time that 

 others are still showing intermittent activity associated with 

 muscle movements. Finally the cilia are in motion, not only 

 along the entire anterior border and lateral processes of the foot, 

 but also over the ventral surface, and in the latter position con- 

 tractions are also going on. At this time the anterior cilia ex- 

 hibit great variation in rapidity of movement. Occasionally 

 they slow down nearly coming to rest in the intervals between 

 contractions, and at other times move so fast that not the slight- 

 est flicker can be seen, the ciliary fringe appearing like a broad 



