140 Transactions of the Royal Society of Victoria. 



manner, but it has not hitherto been observed, that an 

 entire gill, or portion of a gill, when detached from the 

 body is capable of moving visibly and at a measurable rate 

 of speed. It does seem strange, no doubt, that a large and 

 important portion of the body, such as the gill, firmly fixed 

 during life, and playing the part of a stationary engine, by 

 creating currents in the water by means of its cilia, should 

 become when detached, a locomotive engine, and the energy 

 formerly spent in creating currents, now apparently utilized 

 in driving the gill itself And the wonder is not lessened, 

 but increased, when we consider that the sea mussel, 

 provided with such organs, capable when detached, of 

 roaming about pretty actively, is one of the most inactive 

 of animals in the adult state, even rooted to the spot where 

 it lives by means of its byssus. Not only does the gill 

 move thus, but other parts as well, all of them being richly 

 provided with cilia. In fact there are four principal portions 

 of the sea mussel which exhibit this independent movement 

 when detached, viz., the mantle-lobes, the labial palps or 

 tentacles, and the foot, as well as the gills. 



It is generally known that cilia retain their activity even 

 after the death of the animal, and that ciliary motion may 

 be beautifully seen in detached pieces of any of the parts 

 mentioned, but the point now to be insisted on is, that 

 there is visible and measurable movement in these parts 

 when detached. And there is at least a threefold interest 

 attaching to an investigation of this sort. 



There is first of all the peculiarity of detached portions of 

 an animal comparatively high in the scale, retaining to a 

 certain extent independent vitality, moving about and often 

 rotating, as we shall see, in a certain definite manner 

 and direction. Such an appearance is always interesting, 

 whether it be the detached portion of a hydra, or of an 

 earthworm, the wriggling tail of a lizard, or the detached 

 leg of a spider. 



Then there is a further interest when it is known that 

 this movement in the moUusk is due, in whole or in part, 

 to the action of cilia, for it may throw light upon the action 

 of the ciliated epithelium of our own bodies, say of the lining 

 membrane of the nose or of the windpipe. 



And lastly, it will be interesting to determine the 

 functions of the parts when attached to the body, judging 

 from their behaviour when free, and see if such movements 



