128 Messrs. Alder and Hancock on the genus Eolidina. 



Allowing their identity, we can assure him that Proctonotus has 

 an intromittent organ similar to that of Eolis, as we have had the 

 opportunity of seeing it exserted, and have a drawing of it in that 

 state. The argument therefore turns on the other side ; for if 

 M. de Quatrefages has failed to detect it in one animal where it 

 does exist, may he not also have done so in the other ? These 

 are our principal reasons for doubting the existence of the genus 

 Eolidina. We would, however, urge upon M. de Quatrefages the 

 desirableness of again procuring the animal for further examina- 

 tion*. 



M. de. Quatrefages has detached Eolis and the allied genera 

 from the Nudibranchiata in order to unite them with Acteon and 

 some other animals low in the scale of organization, and which 

 seem to form a link between the Mollusca and Planaricef. We 

 suspect that that gentleman, having prematurely determined on 

 this apparently incongruous union, has been hurried too rapidly 



tory appendages on the head, " but forming only one row on each side of 

 the head." 



The number of rows of papillae, however, can only be considered as afford- 

 ing a specific character in this family, and several of the Bolides have the 

 papillae extending in front as far as the sides of the dorsal tentacula. We 

 mention this, not from any doubt that this animal is really distinct from 

 Eolis, but as an example of the deficiency of the characters given as generic. 

 We afterwards learn that the respiratory appendages are continued round 

 the head ; which, with the character of those appendages and other minor 

 points of resemblance, induce us to believe that Zephyrina and Proctonotus 

 are the same, though the latter has two rows of appendages on the sides and 

 round the head, which, according to M. de Quatrefages' views of generic 

 characters, would make them distinct. Our observations on the internal 

 anatomy, however, are much more at variance. In the gastro-vascular sy- 

 stem, our animal had not the longitudinal vessels down the sides of the 

 body, as represented by that gentleman ; yet as all the vessels of that system 

 were coloured in our species, we could not have overlooked them. 



* There are some other points of the anatomy of Eolidina which require 

 further elucidation : for instance, the stomach, according to the figure, is 

 placed remarkably far forward in the system ; nearly in the position, before 

 the dorsal tentacles, which we find the mouth to occupy in Eolis. M. de 

 Quatrefages says that he is confirmed in the opinion of its being the stomach, 

 by having seen in this mass of an analogous animal the back-bone of a small 

 fish. More recently, in his description of Acteon elegans, when speaking of 

 its tongue, which closely resembles that curious organ in Eolis, he says, that 

 at first sight he mistook it for the back-bone of a small fish. Coupling these 

 observations together, are there not grounds for supposing that M. de Qua- 

 trefages has really mistaken the buccal mass for the stomach 1 If so, the 

 diagram representing its connexion with the gastro-vascular system cannot 

 be correct. That Eolidina has a tongue similar to the rest of the family we 

 cannot for a moment doubt, and this, as well as the corneous jaws, will most 

 likely be detected on a re-examination. 



f Of the new genera described, Acteonia is the Limapontia of Johnston 

 (Loudon's Mag. Nat. Hist. vol. ix. p. 79), and Amphorina appears not to 

 differ from Eolis, except in the gastro-vascular system. 



