6 A MONOGRAPH OF THE 



paradoxum, the specific name indicating the extraordinary compound of characters he stated 

 it to possess. To a mouth, he says, as slightly armed as in the Medusae, there succeeds a 

 short canal, ending in a stomachal cavity in which digestion is effected ; when, the more solid 

 parts being ejected again, the liquid and finer products of digestion pass into a branched 

 intestine, the main trunk of which extends down the centre of the body, terminating in a 

 very minute anus. The branches from this central trunk pass off symmetrically on each side, 

 ending, it is stated, in a narrow marginal canal that entirely surrounds the body ; from the 

 lateral branches arise caeca going into the dorsal papillae. These are terminated by an ovate 

 vesicle, through which he conceives the products of digestion to enter into the blood. 

 Accompanying the extensive development of this so-called gastro-vascular system, M. de 

 Quatrefages states that he found the vascular system very incomplete ; the veins had 

 disappeared, and their place had been taken by a system of lacunes without walls, in which 

 the viscera could freely float. At the same time he considered that true branchiae were 

 wanting in this animal, that function being likewise in part performed by the gastro-vascular 

 apparatus. M. de Quatrefages was, we believe, the first to describe the coloured glandular 

 portion of the papillae of these Mollusks, as the true liver broken up into fragments. 



In communicating to the 'Annals of Natural History/ for October, 1843, the discovery of 

 a new Nudibranchiate Mollusk on the Devonshire Coast, possessing a highly ramified digestive 

 system, and referred to the genus Calliopcea, we took the opportunity of expressing our dissent 

 from some of M. de Quatrefages' views, and gave our reasons for believing that his genus 

 Bolidina was founded upon a species of Eolis imperfectly understood. In the same paper we 

 stated that the ovate vesicles, which we had also observed at the ends of the papillae, had an 

 external opening, through which elliptical bodies with long hair-like tails were occasionally 

 discharged.* We likewise announced the discovery of organs of hearing in the Nudibranchs, 

 similar to what M. Siebold had described in the Conchifera and the pulmoniferous Gasteropods; 

 and at the same time gave our reasons for believing that the sense of smell was located in the 

 dorsal tentacles, a statement which subsequent observations have tended to confirm. 



Pursuing still further his investigations into the evidence afforded by these animals of a 

 supposed degradation of the Molluscan type, M. de Quatrefages published, in March, 1844, 

 another memoir on the subject, in which he describes five new genera, named Zephyrina, 

 Acteonia, AmpJiorina, JPelta, and Chalidis ; all more or less deficient, according to his statement, 

 in some of the characters hitherto supposed to belong to the true Mollusca.f Thinking that 

 the anatomical characters he had detected were sufficient to unite them into a group, he 

 proposed to detach the JEolididcs from the other Nudibranchs, and uniting them with the 

 Actaon of Oken, and the genera above mentioned, to make of them a new order, under the 

 name of Phleb enter ata. (The union of functions supposed to be indicated by the peculiar 

 branching of the stomach he afterwards proposed to call Phlebenterism.) The order is 

 characterised as " Gasteropodous Mollusca, with the circulation imperfect or wanting, and 

 deprived of respiratory organs properly so called." 



In all the new genera described in the memoir, neither heart, arteries, nor veins could 

 be found ; the vascular system is consequently supposed to be entirely wanting ; its place 

 being supplied by the branching of the stomach, as already stated. In three of the genera, the 



* This has since been recognised as an urticating apparatus, 

 t 'Annales des Sciences Naturelles/ 3d ser., v. 1, p. 129. 



