HERMiEA. 



Each of the British species would appear to constitute a distinct section. 



Sect. 1. Tentacles with both margins terminating at the side of the head : body cylindrical. 

 H. bifida. 



Sect. 2. Tentacles with the anterior margin continuous with the sides of the head, forming a sub- 

 veil : body with the sides depressed and slightly expanded. H. dendritica. 



Little is known of the anatomy of this genus farther than is revealed through the 

 transparency of the skin ; and though we have had H. dendritica in considerable abundance, 

 it has never been in a fit state for dissection. The compressor, however, has shown us the 

 buccal organ (PL 43, fig. 14) and its dental apparatus. The former is broadly oval, and 

 unprovided with corneous jaws. The tongue (e) is long and narrow, and is furnished with a 

 single row of articulated plates, each bearing a broad tooth or process. The plates (fig. 15) 

 are much shorter than those of Alderia, and the teeth gradually diminish in size towards the 

 anterior extremity, which is very finely pointed and sometimes spirally coiled. This peculiar 

 tapering form of the tongue we have observed only in this genus ; and it no doubt arises from 

 the fact, that the early or first-formed plates are not shed in this as they are in all the other 

 nudibranchs. 



The gastric system is peculiar in Hermcea. In this genus there is apparently no posterior 

 central vessel or hepatic canal, as in the other Eolididce ; but the anterior lateral ones are 

 excessively developed. These in Eolis most commonly assume the form of simple branches 

 inclined forwards, but in Proctonotus and Antiopa, each is made up of two portions, one of 

 which curves forwards, the other backwards. The gastric or hepatic vessels in Hermcea seem 

 to form two continuous lines, one on each of the back, only broken a little near the region of 

 the heart. This break indicates their point of union with the upper surface of the stomach, 

 and that each is composed of two branches, as in Antiopa. One of these branches, as in that 

 genus, passes forwards, and is connected with the glands of the anterior papilla?; the other, 

 passing backwards, is of great length, and terminates in a free attenuated point in the tail ; 

 this branch is connected with the posterior papillae. The whole of these trunk-branches or 

 vessels give off smaller branches, which ramify in various directions ; particularly in 

 H. dendritica, in which those on the side of the body assume a regular dentritic character. 

 It is with these lateral ramuscules that the papillae are connected. All the trunk-vessels 

 and branches are granulated and coloured like the terminal glands, and lie immediately below 

 the skin, and in connexion with it. 



The hepatic gland (fig. 1 6) within the papillae is much branched, and in H. bifida is a 

 beautiful structure, exhibiting another of those simple and instructive modifications of 

 glandular mechanism, so frequently observed in this tribe of animals. The central vessel or 

 duct is linear and slender, and gives origin to numerous subdivided branches, arranged in 

 whorls. The lower portion of the central duct is simple ; and just within the base of the 

 papillae it is encircled with a narrow, almost transparent, belt (b) : at this point the duct is 

 occasionally contracted (c), as if by a powerful sphincter, cutting off all communication 

 between the gland and the gastric or hepatic vessel. The action of this sphincter may be 

 distinctly observed, by the aid of a good pocket lens, when the animal is free and moving 

 about; when first one papilla and then another may be seen thus shut off, and after a while 



