7 34 Proceedings of Royal Society of Edinburgh. [sess. 
when the palps were taken separately they still followed the same 
direction, with the exception of the right outer palp. But it will 
he remembered that it also rotated left-handed as well as right- 
handed, with its inner surface uppermost, so that, generally speak- 
ing, the palps may he said to rotate in the direction of their cut 
margins. And since the palps rotate generally in this direction, it 
might be assumed that the cilia work in the opposite way, and this 
is found to be the case. Thus it is no uncommon sight to see 
matter sweeping across the palp, whilst it is rotating from the 
attached to the free margin, there to be got rid of, and this shows 
unmistakably in what direction the cilia act, at least on that 
surface. Having settled these two general facts, that the palps 
rotate usually in the direction of their cut margins, and that the 
cilia work in the opposite direction, we may now enter a little into 
detail. 
Of the two right palps the inner is particularly active and 
persistent, going at the average rate of 2J minutes per round, and 
continuing its movements for 13 days, while the outer has likewise 
a good record of 3 minutes per round. The direction of rotation in 
both is slightly variable. 
Of the two left palps, the inner is more active, going at the 
average rate of 3 minutes per round ; while the outer is not only 
slower, but the slowest of all the palps. There was here also varia- 
tion in direction of rotation, and it may be assumed that all the 
palps are capable of it. 
The palps on the two sides of the body are thus pretty evenly 
balanced, as far as movement is concerned, but the advantage on 
the whole evidently lies with the right side. 
Function . — In detached palps it is very easy to observe the 
direction in which matters are carried by them. In the course of 
rotation it was observed, more particularly in the left inner and 
left outer palp, both lying as they naturally do with their inner 
surface uppermost. In the left outer the dirty matter was sent 
spinning across from the inner to the outer margin, where it formed 
into slimy threads along the outer edge. There it gradually became 
parted off from the body of the palp, separating from the tip end 
first, and latterly it formed a streamer, carried round by the re- 
volving palp. Ultimately the matter was got rid of entirely, and 
