732 Proceedings of Royal Society of Edinburgh. [sess. 
On the 13th day the curve of progression was not passed 
through, and movement ceased altogether on the 14-th day. 
The right inner palp, with a renewal of water once, was 
actually engaged in rotation for the space of 11 days, and, if the 
rotating detached palps of oyster and sea-mussel were kept in 
constantly moving sea water, it is hard to say how long they might 
not continue their movements. 
The day after rotation ceased the palp was examined under the 
microscope, and the cilia were still in active motion except at the 
tip end, where the long cilia moved hut sluggishly, and were almost 
still. Now that rotation had ended the next point to determine 
was, how long the “ ciliary motion” might last after such a display 
of energy. On the 15th day, as just mentioned, the cilia were in 
motion all round, hut most actively in the curved part. Here 
material was being passed along in the direction of the arrow and 
thrown off at the anterior end. Later on, this end was found to 
move a little backward, while the tip end remained fixed. 
On the morning of the 16th day the anterior end was found to 
have moved hack nearly inch, while the tip end was stationary. 
Microscopic appearances explained this, for ciliary motion was now 
seen to he confined to the curve a, where the cilia were still working 
actively. On the evening of the same day no further movement 
had taken place, only a slight movement at the tip end. Under the 
microscope, the tip was seen to have tucked itself in a little (hence 
the motion), and the cilia were still active in the curve, more particu- 
larly towards the very anterior end. On the morning of the 17th 
day, there was no change of position, and under the microscope no 
ciliary motion was observed. The cilia stood out like a fringe in 
the curve, perfectly still ; the cilia had thus ceased to move not all 
round at once, but in patches, as it were, and as far as observed in 
the specimen in the following order: — At the tip end first, round 
the outer margin next, and on the attached margin nearest to the 
mouth last of all, where the cilia had a powerful appearance. 
The ciliary motion lasted at least up to the evening of the 16th 
day, while the rotatory motion ended on the 14th day. And 
taking the last observation for the ciliary motion, it exceeded the 
other by 2 days 9 hours. 
The palp, as it lies in the clear sea water, still retains its colour. 
