DENTALIUM. 231 
rior part of the body would be destroyed, and its vermicular 
motion, to aid and accelerate the passage of the branchial 
fluid and its expulsion through the comparatively narrow 
medial duct, paralysed. I may state im corroboration of the 
foregomg observations, that I have removed the posterior 
hyaline process and enlarged the orifice as much as possible, 
and then dropped therein some grains of fine sand to irritate 
the membranous spoon-shaped process, when instantly pure 
water, without the slightest admixture of feecal substances, 
was ejected ; and this result was invariable in all, and many, 
individuals. 
I have stated that in young transparent specimens an unin- 
terrupted but slow action of systole and diastole might be 
observed, and was apparent from the distinct ascent and de- 
scent of the water in the branchial canal; but this action 
cannot take place in a merely excretory tube; it can only 
exist in a circulatory, or inhalant and exhalant one. I have 
carefully dissected the body from the branchize to its terminus, 
and submitted its substance to microscopic powers, without 
discovering a trace of an intestine, which is usually the easiest 
organ to be detected by its colour and distension. I have 
carefully watched thirty individuals at a time, and never saw 
any rejectamenta from the posterior process ; but in the same 
period frequent discharges anteriorly from the centre of the 
mantle, of foraminiferous spoil enveloped in mucus. I finally 
observe, that on the animal bemg removed from the shell, 
the medial branchial canal is distended, but in a short time 
collapses from the evaporation of the fluid, and exhibits a 
deep canaliferous groove; and when the canal is not quite 
full, one or two globules, precisely lke those of a spirit-level, 
may be made with the slightest pressure to float backwards 
and forwards from the posterior sphincteroid process to the 
branchize. Many other circumstances can be added in proof 
of the posterior entry of the branchial water, but I have 
already transgressed the limits of conciseness, and it is time 
to take some notice of the nervous system, salivary glands, 
the stomach and its contents, and the substances whieh fill 
up the body from the branchize to the posterior terminus. 
