ON THE BRITISH ANNELIDA. 241 



which lie on each side of it. All that portion of the body in which the 

 common cavity is continuous and dilated consists of one annulus, but the 

 succeeding or terminal is composed of a great many, each about the eighth 

 of an inch in length. 



Each of these separated annuli contains all the elements of the perfect or 

 original animal, viz. a male and female generative apparatus, the cavity com- 

 mon to the generative, digestive and respiratory Junctions. Serpentaria 

 therefore is a composite animal, each perfect individual consisting of numerous 

 and apparently still unformed or imperfectly formed individuals. 



With respect to Nemertes, Mr. Goodsir makes the following observations. 

 Anterior extremity of the body rounded, somewhat quadrilobate, M'ith the 

 proboscidean orifice in the centre. Male generative apertures on each side. 

 Cloaca or abdominal surface immediately behind. The anterior extremity 

 is slightly quadrilobate, and in the centre there is a small foramen, through 

 which a long, narrow, extensile, trumpet-shaped probos(;is can be protruded 

 at the will of the animal. On each side of these are two narrow longitudinal 

 slits similar to those in Serpentaria ; these, as already mentioned, are aper- 

 tures to the male generative apparatus, which consists of two long, narrow 

 cellular tubes, running down each side of the body. The cloaca on the 

 abdominal surface of the body is small and rounded, and opens into an oblong 

 cavity similar to that of Serpentaria. With reference to an alleged orifice 

 at \}s\^ posterior termination of the body, Mr. Goodsir states that the opening 

 was so large that it appeared in process of filling up after the last separation, 

 admitting thus the fact of the existence of a terminal anal orifice. This 

 excellent observer proceeds to remark, "that the leading features in the 

 structure of both these species are similar. The large common cavity in 

 both species is common to the respiratory, digestive and generative systems. 

 The water in which the animal lives is transmitted through this cavity, and 

 thus acts as a means of respiration. In Serpentaria it acts I would say al- 

 most altogether as an organ of digestion, and for this purpose its construction 

 is slightly different from that of Nemertes, in which animal the structure 

 approaches more to that of the true Planaria, in so far as it is endowed with 

 an extensile'trumpet-proboscis, which is continuous with a large puckered-up 

 tube running along the upper and central part of the common cavity, and 

 which, contrary to the supposition of Rathke and other naturalists, is, accord- 

 ing to the opinion already expressed by Ehrenberg, the intestinal canal. It 

 is tied down at intervals by strong filjrous or muscular bands (mesentery), 

 which, when unwound, allows the intestine to escape IVom its attachments. 

 The ovaries which run down on each side of the body have no means of 

 throwing off the ova except into the common cavity. It appears to me 

 therefore that Ehrenberg is correct in supposing that cavity to be an egg- 

 passage, and in Serpentaria this is more fully shown than in Nemertes." 



From the preceding quotations it is obvious that Mr. Goodsir's ideas with 

 reference to the anatomy of the Nemertinidce are by no means clearly defined ; 

 he first states that there exists a terminal anal orifice, while at the same time 

 he describes the presence of a cloaca on the abdominal surface not far from 

 the head ; he affirms that the water is admitted directly into the great cavity 

 of the body, contending at the same time that in this cavity the threefold 

 office of respiration, digestion and generation is discharged. It will be here- 

 after shown that the views of Mr. Goodsir, in relation to the plan of structure 

 on which these eccentric Annelids are organized, differ most widely from 

 those to which the author of this Report has been conducted by his own 

 investigations, and which are now published for the first time. 



1851. R 



