LAND CRUSTACEANS. 79 



that which is outermost at its origin from the mesocardiac ossicle passes under the middle 

 one and is attached posteriorly between this latter and the inner band'. 



The cardiac disks are provided, as in the other Pagurinea, with dilator muscles, running 

 forward to the cephalic wall. Mocquard'-, discussing the working of the gastric musculature 

 of the Decapoda, concludes that the function of the dilators of the stomach^ is, by en- 

 larging its cavity, to draw into it fluids, carrying with them the solid particles of the 

 food. On the relaxation of the dilators, the constrictors^ of the stomach will drive out 

 the liquid, while the solid matters will be caught on the filter provided by the hairs on 

 the cardiac disks or elsewhere near the opening of the oesophagus. This theory is very 

 plausible, but there are considerable difficulties in the way of its acceptance in the case 

 of the genus Cuenobita at least. For the great majority of the food is by these creatures 

 eaten absolutely dry, with only such juices as it naturally contains. If, for instance, an 

 individual be watched in the act of consuming one of its most common articles of food 

 — the fruit of the Pandanus — it will be seen to hold the food firmly with the great chela, 

 while the smaller one is employed in stripping off the fibres of the fruit and placing 

 them between the maxillipeds of the third pair, which open to receive them, and then 

 pass them on towards the mouth. They are not immediately rejected, and presumably 

 are sent into the stomach after having undergone a first crushing by the mandibles. In 

 any case the powerful gastric teeth argue a mastication of some part of the food there. 

 Now the Pandanus-£bres, and indeed the majority of the food of all sorts, cannot be 

 supposed to contain enough moisture to convey the solid part to the stomach, however 

 much it may be broken up by the mandibles. And the fact that the stomach, when 

 opened, contains but little fluid, precludes the suggestion that its watery contents, passing 

 backward and forward, continually perform the same function of carrying solid food from the 

 mouth to the stomach. 



These considerations appear to conclusively negative Mocquard's theory of swallowing 

 in the Decapods. For, although the same difficulty does not exist in marine forms, the 

 similarity of the mechanism in the two cases makes it difficult to suppose that a different 

 method is adopted in each. The subject is at all events worthy of further investigation. 

 It may prove to be the case that the more liquid part of the f)od is swallowed in the 

 way described by Mocquard (and suggested before him by Parker') while the moie solid 

 portion is either rejected or swallowed by some other mechanism, as, for instance, by the 

 constrictors of the oesophagus. 



B. The Mid-gut". (PL III. figs. F, G.) As in other Decapods, the stomach of Coeno- 



^ The mode of action of the gastric mill of Decapoda is half of the stomach, are described by Mocquard ; the autero- 



discussed in Mocquard's paper and in Huxley's "luverte- superior (on the cephalic disk), the anteroinferior, the an- 



brates." Briefly put, it is as follows : — The contraction of terior and the posterior lateral. 



the anterior and posterior gastric muscles has the result of * Of these there is one on each side — a band of fibres in- 

 bringing the three teeth (median and lateral) together. On serted on the cardiac wall at the front end of the side-plate, and 

 their relaxation the ossicles return to their normal position running downwards and a httle forwards to the oesophagus, 

 by the elasticity of the stomach-walls, and also partly by the ^ T. J. Parker, Journ. Aitat. Phya. xi, p. 59 (1870). 

 action of the eardiopyloric muscles. '' Bouvier, in a short article " Sur la Respiration et quel- 



- Mocquard, Ann. Sci. Nat., (7), xiii. 3, p. 3 and xvi. 1, ques dispositions organiques des Paguriens terrestres du 



p. 255. Genre C^nobite " [Bull. Soc. Fhilonmth., Paris, (8) ii. p. 194 



* Of course the above-mentioned dilators attached to the (1839)], remarks briefly on this aud other internal organs of 



cephalic disks, though they are the chief, are not the only Coenobita. His observations were made on C. diogenes, and 



ones. Setting aside the dilators of the oesophagus and those it is interesting to find that, so far as they go, they support 



of the pyloric division, the following, attached on the cardiac mine, which relate to the Indo-Pacific species. 



