348 Zoological Society. 



EXPLANATION OF PLATE XIIL 



This plate is designed to express, in outline plans, the natural manner in 

 which the alimentary system of the Cestoid and Trematoid Entozoa passes 

 into that of the Nemertine and Planarian Annelida — that they are really 

 constructed upon one and the same principle. Though not represented in 

 this series of figures, the system of the nutritional fluids in these Entozoan 

 and Annelidan groups conforms to one type. The channels for the fluids 

 difier little in distribution from those of the alimentary system. 

 Fiff. 1 . Alimentary system of Nemertes Camilla, the caeca {b) of which are 

 charged with a corpusculated chyme ; e, space external to the 

 latter system filled with the chylaqueous fluid ; d, shows that the 

 true alimentary organ of this worm, in common with that of all 

 Nemertine Annelids, is closed at all sides ; a, oesophagus enter- 

 ing the proboscis. 

 Fig. 2. The caudal end of the alimentary organ of another Nemertine An- 

 nelid, Borlasia ?, proving it to be csecal also at this extre- 

 mity : a, cavity ; c, cajca of this organ filled with a corpusculated 

 fluid ; b, space external to the alimentary caecum filled with chyl- 

 aqueous fluid. 

 Fig. 3. Alimentary system of a Planaria : b, mouth ; c, caeca ; a, areolae 



external to the digestive diverticula. 

 Fig. 4. Digestive system of a freshwater leech, Clepsina — — ?: a, caeca 



filled with corpusculated chyme. 

 Fig. 5. Ideal, transverse, section of Aphrodita aculeata, showing the dis- 

 tribution of the alimentary system, and its relations to that of the 

 nutritional fluids : a, stomach ; b, visceral cavity ; c, scales, by the 

 rising and falling of which a strong current of sea-water is main- 

 tained through the dorsal channel (e), by which current the fluid 

 contents of the digestive caecum {d) are aerated. 

 Fig. 6. Alimentary caecum of one segment of Tcenia Solium : a, mouth of 

 this segment leading into a short oesophagus (6), and thence into 

 the ramifications (c) of the digestive system. 

 Fig. 7- Alimentary system of a Trematoid Entozoon : a, oesophagus ; 



b, digestive caeca. 

 Fig. 8. Ditto of Amphistoma : a, b, caeca of digestive system. 

 Fig. 9, Ditto oi Bothriocephalus latus (a sterelminthous worm) : a, mouth 



of a single segment ; b Sc c, caeca of digestive system. 

 Fig. 10. Plan of a Nematoid worm, showing the great diff^erence between 

 the diameter of the intestine (a) and that of the space (c) enclosed 

 by the integuments ; b, reproductive organ. 

 Fig. 11. Another type of a Nematoid Entozoon {Ascaris lumbricoides), in 

 which the intestine (a) is larger m diameter, and tied by fi'equent 

 bridles (b) to the dense integuments (c). 

 Fig. 12. Transverse section of the same. 



[To be continued.] 



PROCEEDINGS OF LEARNED SOCIETIES. 



ZOOLOGICAL SOCIETY. 



July 22, 1851.— J. E. Gray, F.R.S. &c., Vice-President, in the Chair. 



On the Arrangement of the Edentate Mammalia. 

 By H. N. Turner, Jun. 

 In offering to the Society a summary of my observations on the 

 craniology of the Edentate order, I have not so great a number of 



