64 Proceedings of the 



Annelides. Immediately beneath, or internal to the muscular 

 bands, and corresponding with them in length and breadth, 

 are eight canals excavated in the gelatinous tissue of the ani- 

 mal, and connected by a system of transverse branches with a 

 much larger cavity, which occupies the axis of the body along 

 its whole length, and admits the sea-water by two orifices 

 situated at its inferior extremity, capable of being opened or 

 closed at the will of the animal. The whole of these canals 

 form a water-vascular system, through which a constant cir- 

 culation of fluid takes place, urged by the fine cilia with which 

 the cavities are lined. 



The digestive system consists of a flattened sac, about two- 

 thirds the length of the animal, suspended within the large 

 central canal of the water- vascular system. The upper ex- 

 tremity of this sac terminates in a linear mouth situated on 

 the upper surface of the body, while its lower extremity opens 

 into the large canal in which it is inclosed, so that the pro- 

 ducts of digestion are (as in Actinia) at once admitted into the 

 main cavities of the body, in which the functions of nutrition 

 and respiration are carried on together. There also exist two 

 other large cavities in the body connected with the water- 

 vascular canals, which serve as receptacles for the tentacular 

 apparatus, the use of which has caused much difference of 

 opinion amongst writers on this branch of Natural History. 



As far as I have been able to ascertain, nothing is certainly 

 known as to the reproduction of Cydippe. Siebold (in his work 

 on Comparative Anatomy) has stated that Mertens has observed 

 detached corpuscles from the body of Cestum and Cydippe 

 swimming freely about and rapidly enlarging, but that his 

 observations were there limited. Professor Grant has imagined 

 that he has detected ovaries, consisting of two lengthened 

 clusters of small spherical gemmules, of a lively crimson colour, 

 extending along the sides of the stomach ; but his description 

 of the anatomy of Cydippe is so inaccurate, that his remarks 

 on its ovarian system are not to be relied on. Mr Robert 

 Paterson of Belfast (who has written an excellent monograph 

 on this Acaleph) has not been able to verify Dr Grant's ob- 

 servation, although he has examined several hundred speci- 



