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 in corroboration of the 

 foregoing 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 faecal 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 branchiae 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 being 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 like those of a spirit-level, 

 may be made with the slightest pressure to float backwards 

 and forwards from the posterior sphincteroid process to the 

 branchiae. 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 which fill 

 up the body from the branchiae to the posterior terminus. 



