1^6 Prof. G. J. AUman on the Anatomy of Actseon. 



extremity of the branchial appendages as M. de Quatrefages de- 

 scribes under the name of cloaca*. The length of the oesopha- 

 gus and the form of the stomach are altogether at variance with 

 his description. The oesophageal collar consists of seven, not 

 four, ganglia ; and if to these points of discrepancy we add some 

 others mentioned in the present paper, and call to mind that he 

 has totally overlooked the salivary apparatus and made no men- 

 tion of the highly-developed generative system, we cannot but 

 conclude that the establishment of a new order of animals on ob- 

 servations so imperfect is unwarrantable and rash. 



But suppose the observations of the French zoologist not al- 

 together so erroneous as is here maintained, is he yet justified in 

 the step which he has taken ? We assuredly think not. 



Let us consider for a moment whether the singular ramified 

 system connected with the stomach in Actceon and other allied 

 genera is really of that vast importance in a zoological point of 

 view with which M. de Quatrefages would invest it. If the sy- 

 stem in question be merely a ramification of the stomach, we can 

 certainly see in it a disposition by which the surface of the gastric 

 cavity is greatly increased ; but this disposition, exercising no 

 marked influence over the organism, cannot be supposed to de- 

 mand any important modifications in the other organs, and surely 

 ofiers no solid grounds for believing that its ofiice is to expose 

 the products of digestion to the influence of the aerated medium. 

 In truth it is ill-adapted to this function, separating its contents 

 from the surrounding fluid, not only by its own walls but by the 

 intervention of a portion of the cavity in which it floats, and by 

 the whole thickness of the integumentary structures. 



But it may be asked, what office is it possible to assign to the 

 system now under consideration, if it be not that of respiration ? 

 I believe that the ramified apparatus in Actceon and the EolididcB 

 is truly a hepatic system, and affords an interesting example of 

 the reduction of a gland to one of its simplest conditions f. 



We have in these gastric ramifications one or more offsets from 

 the lining membrane of the alimentary canal greatly extended 



* We can in no way explain what M. de Quatrefages intended by the 

 organ which he describes as a cloaca, unless we suppose that he really meant 

 the oval sac (y, PI. VI.) in the posterior part of the body, which we have de- 

 scribed in connexion with the generative system, and which by some strange 

 confusion he has transferred to the posterior extremity of the branchial ex- 

 pansions. 



t Since the opinions here expressed were laid before the Association, 

 there has been placed in my hands a number of the * Comptes Rendus,' con- 

 taining a paper by M. Souleyet on the Phlehenterata (Annals, xiv. p. 342), 

 in which I find that the author's observations on this subject are entirely in 

 accordance with my own. 



