SCHIZOPOD PKOM TASMANIA. 293 



and it was a matter of difficulty — and in some cases of impossibility — to separate them 

 one from another or from the adjacent tissues. 



In not a single specimen could I isolate the heart throughout its length or trace the 

 course of the principal blood-vessels. The same remark applies to the hepatic tubes, 

 which were completely disintegrated except at tlieir extremities. This has necessarily 

 led to an incomplete and imperfect resolution of many details of structure. The best 

 results in regard to the soft parts were obtained by means of sections. 



Alimeittury system. — The oesophagus is very short and passes vertically into the 

 stomach (PL XXVI. figs. 1 and 6). The latter is an o^ien sac. curving over nearly at 

 right angles to the gullet and passing directly back into the intestine ; it is of very simple 

 structure as compared with the usual structure of this organ in the higher Crustacea. 

 In front, and just where it widens from the oesophagus, the median line is chitinized into 

 a stout ridge which thickens upAvard into a club-shaped process, covered at its extremity 

 with tine tooth-like rugosities, and projects into the cavity of the stomach (fig. 7). 

 Above this process the median ridge bends over to form the dorsal ridge of the stomach, 

 and this thickening is continued back as far as the fourth thoracic segment. On each 

 side of the base of this line the chitinous thickening is expanded into a t\vo-lol)ed pro- 

 cess, ending in sharp and somewhat widely separated points. At the posterior side of the 

 mouth-opening there arise two stout chitinous ridges densely covered, especially at their 

 base, with setiu or curved bristles, all pointing inwai'd. Thus the opening of the stomach 

 is guarded by so many projecting processes that it must be almost impossible for food to 

 be again ejected at tlie gullet. On each side of the frontal median ridge the stomach 

 is produced into two curved concavities occupying the front portion of the cephalic 

 segment almost to the bases of the antennae aad the ocular peduncles. The base 

 of the stomach, reaching back from the oesophagus to n ear the fourth segment of fue 

 body, is chitinized, and the bands on each side of it are thickly ciliated (tig. y). Tvvo 

 other ciliated bauds pass up the sides and converge towards the median band, forming 

 along with it the roof of the cavity. The side-wails of the stomach between the chitinous 

 bands are very thin and membranous, and are protected by tlie dense mass of muscles 

 of the mandibles. The whole of the stomach and part of the fore-gut appear to be 

 covered by a longitudinal sheath of muscular tissue. Except the clu]>-shaped projection 

 in the front of the stomach, there seems to be no special masticatory apparatus, and 

 trituration of the food appears to depend on the up-and-down movement of the whole 

 upper part of the sac. Maceration of the food is certainly very imperfectly effected, as I 

 have investigated the contents of the intestine and found that so far back as the seventh 

 thoracic segment fragments of Copepoda, &c., occurred, in which the integuments and 

 portions of the limbs were still intact. I think it probable that the hepatic tubes open 

 into the alimentary canal just at the posterior end of the stomach or at the very com- 

 mencement of the intestine ; but neither by dissection nor by longitudinal and transverse 

 sections could I detect the opening, although the tubes themselves were in several cases 

 followed up to this part of the canal. 



Erom the stomach the intestine proceeds back as a straight, simple, and rather wide 

 tube ; for about the posterior half of its length the wall is wrinkled into small folds, as 



SECOND SERIES. — ZOOLOGY, VOL. VI. 39 



