TRANSACTIONS OF SECTION D. 413 



i 



surfaces under water. Various conditions, normal and experimental, in which it 

 is, however, employed with effect. 



III. The locomotor action of the lantern is a particular manifestation of a 

 rhythmic functional activity, which can also subserve feeding, boring, respiration, 

 and possibly also the maintenance of physiological turgescence in various internal 

 cavities. 



6. The Dorsal Vibratile Fin of the RocMing (Motella). 

 By J. Stuart Thomson, Ph.D., F.R.S.E. 



It has been suggested by Bogoljubsky and others that the dorsal vibratile fin 

 of Motella is a ' lure.' functioning in a somewhat similar manner to the anterior 

 filamentous process of the fishing-frog, Lophhis piscatorius. 



The object of the present paper is to show that the function of the vibratile 

 rays is to produce a current of water over numerous terminal or taste buds situ- 

 ated on the skin in that region of the body. This part thus functions as a highly 

 efficient gustatory organ. These taste organs are distinguished from the neuro- 

 masts or lateral line organs by the following points : (1) The sensory cells extend 

 from the external ectoderm to the internal limiting membrane ; (2) the organs 

 are not enclosed in pits, canals, or tubes, and (3) they are innervated by the 

 recurrent facial (ramus lateralis accessorius), which has its root in the facial lobe 

 of the medulla. The facial lobe has been described by Herrick as part of the 

 gustatory tract. 



While it is more than probable that in certain cases the vibratile motion of the 

 free rays may attract animals to the proximity of the taste buds of this region, 

 and thus bring food within the sphere of physiological action, in other cases it is 

 impossible that this apparatus could function as a ' lure,' as the food in these 

 instances consists of animals which have slight or no visual power. It is evident 

 that in many cases the animals upon which the Eockling feeds come quite 

 accidentally near the taste glands, and the current, of water produced by the 

 vibrating rays aids in locating or detecting food. 



One has to distinguish in fishes (1) an olfactory reaction, i.e., an aimless 

 circling movement; (2) a gustatory reaction, i.e., a sharp turn of the body and 

 instantaneous seizing of the bait ; and (3) a tactile reaction. 



From the author's experiments there could be no doubt of the existence of a 

 purely gustatory reaction. Some of the most successful responses were obtained 

 on placing Arenicola in proximity, but not in actual contact, with the taste 

 buds of the region under consideration. 



Bateson has previously noted the presence and physiological significance of 

 terminal buds on the barbules and pelvic fins of Motella. 



7. Variation in a Medusa. By C. L. Boulenger, M.A. 



8. Report on the Occupation of a Table at the Zoological Station at Naples. 



See Reports, p. 119. 



9. Report on the Index Animalium. — See Reports, p. 120. 



10. Third Report on the Feeding Habits of British Birds. 

 See Reports, p. 128. 



11. Report on the Biological Problems incidental to the Belmullet Whaling 

 Station. — See Reports, p. 121. 



