NUDIBRANCHIATA. 559 



Fam. Doridopsidae'. 



The Doridopsidae externally much resemble the cryptobranchiate Dorididae but differ 

 in their internal structure, particularly in the buccal parts. The body is soft, often gelatinous : 

 the back either smooth or covered with soft warts and tubercles. The rhinophores perfoliate 

 and retractile. The branchiae retractile into a common pocket, generally rather large, few 

 in number and tri- or quadripinnate. The foot broad, grooved in front with a notch in 

 the upper lamina, not extending behind the mantle. Tentacles small, not projecting freely 

 and resembling two folds, sometimes hardly distinguishable. The mouth is a fine pore, 

 usually situated in the anterior cleft of the foot: there is no trace of jaws, radula, or labial 

 armature and the buccal organs consist of a slender suctorial tube which can be protruded 

 as a proboscis through the mouth pore. Beneath the anterior part of this tube are two 

 large folliculate glands called ptyaline. The true salivary glands appear to be represented 

 by two nodules at the commencement of the oesophagus. The stomach is surrounded by 

 the liver, which is bifid behind. The nervous system is extremely concentrated. On the 

 interior dorsal wall of the pericardium are a number of folds, sometimes called the pericardial 

 gill, though their respiratory functions are not clear. The hermaphrodite duct is spread 

 over the liver and there are two spermatothecas. There is an armature of minute hooks 

 on the spermatic duct and the glans. 



The Doridopsidae are clearly allied to the cryptobranchiate Dorids by their retractile 

 gills and general structure, but can usually be distinguished externally by their soft con- 

 sistency and pore-like mouth in the anterior pedal groove. The suctorial mouth allies them 

 to the Phyllidiadae, especially Phyllidiopsis, and the details of their anatomy (the concentrated 

 nervous system, the pericardial lamellae and the penial armature) present remarkable re- 

 semblances to that family. Whether they are phylogenetically more akin to the Dorids or 

 the Phyllidiadae can only be proved, if ever, by the discovery of connecting links, but the 

 present evidence seems to bring them nearer to the former than to the latter group. They 

 differ from the Dorids mainly in the buccal parts, which may be easily modified by diet, 

 but from the Phyllidiadae in their general shape, texture and respiratory organs. The 

 concentrated nervous system and reproductive armature are found in several Dorids and it 

 is not clear that the pericardial lamellae are a character of importance. 



The fixmily contains more than 60 species arranged by Bergh in two genera, Doriopsis 

 and Doriopsilla. The latter, which contain only one certain species, is characterized by the 

 body being hard and by the buccal ganglia being situated at the anterior not the posterior 

 part of the buccal tube. The genus Doriopsis (or Doridopsis), though apparently not found 

 in the colder seas is probably cosmopolitan in warm waters, being recorded from the 

 Mediterranean, the West Indies, and most parts of the Pacific and Indian Oceans. The 

 animals are generally abundant under stones on coral reefs. Their food is unknown. In 

 captivity I have never seen them take nourishment, though they crawl over stones and 

 sponges as if seeking for something to eat. 



' Pease, Proc. Zool. Soc. London, 1860, Amer. Journal DeuUchen Malac. Gesell. vi. 1879. Id. Die Doriopsen des 



Conchol.vi. 1871. Hancock, On the Anatomy of Doridopsis, Mittelmeeres , ib. vn. 1880. Id. Challenger Report on Nitdi- 



1865. Alder and Hancock, Notes on a Coll. of Nud. Moll. branchy 1884. Id. in S. R. Heft x. Supp. Heft i., Heft xv., 



from Madras, 1863. Bergh, "Neue Nacktschnecken der xvi., xvn. Id. Die Nudibranchiata holohepatica Porostonuita, 



Sudsee," Journal Mux. Godeffroy, Heft viii. 1875, Heft xiv. Wien, 1892. 

 1878. Id. "Die Doriopsen des Atl. Meeres," Jahr. dcr 



