1888 .] 
Mr D. Alpine on Bivalve Molluscs. 
203 
8th. Food consists principally of diatoms of various kinds, ova 
and spores (including its own reproductive elements). 
9th. Particles strained off by the gills probably do not enter the 
mouth, but ultimately leave the body. The counter currents of the 
muscular margin of mantle-lobe carry particles within reach of the 
mouth, and the converging and diverging currents in the confined 
space at the anterior end assist in this action. 
10th. Motive power exerted by the gills when detached is equal 
to lifting its own weight 1 inch in 7 minutes or y inch in 1 minute. 
The ciliated cells of the frog’s epithelium are calculated similarly to 
do J- inch. But in the case of the gill there is the clinging force to 
overcome in addition to the force of gravity, and approximately 
estimating this force and allowing for it, the gill raises its own 
weight at least f inch in 1 minute, or does between three and four 
times more work than the frog’s ciliated epithelium. 
The movements are not entirely due to the action of cilia, 
muscular contraction playing a most important part in altering the 
shape and dimensions of the part, and in giving it outlines which 
enable it to get rid of obstacles, or to make a more judicious use of 
its motive power. 
The ciliary and other activity of all these parts is stimulated by 
direct mechanical irritation, ample proof of this being obtained by 
numerous experiments. It appears, too, that there is just as much 
reason to recognise volition in the detached parts as in the ciliated 
infusoria, from the fact that the direction of the moving pieces of 
gill is so frequently changed as they pass from point to point on a 
moistened plate. In the common sea-mussel there is a latent power 
of independent movement in the entire animal as well as in the 
detached parts which has hitherto escaped notice. 
[Table 
