366 



THE GENUS DORIOPSILLA Bergh. 



By sir CHARLES ELIOT, K.C.M.G. 



(Read before the Society, September 12th, 1906). 



In \}ii\% Joiir7ial (antea pp. 254-5) I described ^'^tcxmtw?, oi Doridopsis 

 miniata Alder & Hancock under that name and stated that they had 

 the central nervous system arranged as in Doridopsis. A further 

 examination, however, made with sections has shown me that this 

 statement is incorrect and that the nervous system is as in Doriopsilla. 

 The species must accordingly be called Doriopsilla miniata (A. & H.). 

 The difference between the two genera is that in Doriopsilla the buccal 

 ganglia lie immediately behind the rest of the nervous system, whereas 

 in Doridopsis they are situated some way back on a constriction of the 

 oesophagus and are united to the central nervous system by rather long 

 connectives. Not only is it often difficult to determine the position 

 of the buccal ganglia in preserved specimens by ordinary dissection 

 but the digestive tract of Doriopsilla is supported by threads which 

 can easily be mistaken for the long buccal connectives of Doridopsis. 



Though the position of the buccal ganglia may seem a somewhat 

 minute character, it is of considerable structural importance, for it 

 would appear that these ganglia must be regarded as marking the 

 commencement of the oesophagus, whereas the part of the ahmentary 

 tract lying in front of them corresponds to the buccal mass of Dorids, 

 which possess a radula. The difference between the arrangements 

 found in Doridopsis and Doriopsilla is further explained and illustrated 

 in a paper by me on the Nudibranchs of Southern India and Ceylon 

 which will shortly appear in the Proceedings of the Zoological Society. 



I have also examined by sections the animal described by me as 

 Doridopsis reticulata Cockerell & Eliot {/ourn. Malacol., vol. 12, p. 41, 

 1905) and think that it is likewise referable to Doriopsilla. The real 

 buccal ganglia are not, as stated, 4 mm. behind the central nervous 

 system but immediately behind it and are united by short connectives 

 to the part that seems to correspond to the pleural ganglia. The 

 arrangement of the alimentary tube differs in some particulars from 

 that found in D. /niniata. The part in front of the nerve collar is 

 broad and pouch-like. Just under the nerve collar is a valvular 

 apparatus, separating this anterior dilated portion from the narrow 

 posterior portion, which is long and bent. Before entering the liver 

 the alimentary tube dilates again into a pouch, divided by the con- 

 striction. Under the buccal parts was found a large bilobed gland, 

 but its connection with the alimentary tube, though probable, could 



