242 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
tube-foot, and are separated from its cavity by a delicate 
lining of ill-defined epithelial cells. They are wholly 
longitudinal in every species examined. On approaching 
the terminal sucker (Asterias, Solaster) the fibres converge 
towards its centre, from which point they are distributed 
in beautifully regular radiating strands to its periphery. 
External to the muscular layer is (1) a layer of connective 
tissue; (2) a layer of nerve fibrils with ganglion cells; (8) 
an epithelial layer in which the cclls are of considerable 
length, and consist of supporting cells, sensory cells, and 
gland cells, the latter occurring largely in the sucker; and 
(4) the structureless cuticle. It seems to me that con- 
traction of annular fibres such as Romanes described would 
result rather in the extension of the tube-foot at the 
expense of its diameter, for a valvular arrangement 
prevents the reflux of the contained fluid from the tube- 
feet into the radial water-vessel. Extension 1s, moreover, 
brought about by the contraction of the ampulle, while 
the longitudinal disposition of the muscular fibres is quite 
sufficient to account for all contractile movements. The 
second statement, with reference to complete retraction of 
the tube-feet within the body of the animal is entirely 
without foundation. Even after immersion in the strong- 
est alcohol the tube-feet are never so retracted. ‘The 
ectodermal and nerve layers are certainly thrown into 
numerous annular folds, and it is possible that a super- 
ficial examination of these led Mr. Romanes to describe 
them as annular muscles. 
List of works referred to in the text. 
1. Durham, H. E.—‘‘On Wandering cells in Hchino- 
derms, etc.,’’ Quart. Journ. Micr. Sci., XX XIII, (1891). 
2. Cuénot, L.—‘‘ Contributions a |’ Etude anatomique 
des Astérides,’ ‘Theses prés. Fac. d. Sc.,’ Paris, 1887, 
