UOUSAL V1J3RATILE FIN OF THE EOCKLING (MOTELLA), 241 
The Dorsal Vibratile Fin of the Rockling 
(Motella). 
By 
J. Stuart TIioiiisoii, Pli.D., F.L..S., F.R.S.F., 
Lecturer and Senior Demonstrator in Zoology, University of 
Manchester. 
With Plate 11. 
Most collectors on our shores are familiar with the 
rocklingj and have observed the series of free, vibrating 
rays situated slightly anterior to the ordinary dorsal fin. It 
is the object of the present paper to give an account of this 
vibratile fin, together with co-related parts, and to indicate its 
function as a whole. 
Bogoljubsky holds that this vibrating fin has not any 
physiological function other than that of a “lure,” which is 
supposed to act in a somewhat similar manner to the anterior 
filament in the fishing frog or angler-fish, Lophius pisca- 
torius. This explanation does not appear to me satisfactory, 
especially as no suggestion is made as to the precise method 
by which this supposed “ lure,” situated some distance 
posterior to the mouth, acts. From the standpoints of 
morphology and physiology I have come to the conclusion 
that the part has to be regarded as a highly efficient 
gustatory or food-detecting and food-locating organ. 
The two species of rockling most commonly collected on 
our shores, and on the bottom in deeper water, are the three- 
bearded rockling, Motella tricirrata, and the five-bearded 
rockling, Mo tell a mustela. As regards the habits of these 
fish, one may notice that they are shy, nocturnal, phlegmatic, 
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