242 
J. STUART THOMSON. 
iioii-predaceous, and, as was pointed ont by Bateson some 
years ago, do not, as a rule, seek oi- find their food by sight. 
On the sea-shore, the recklings are mostly found lurking under 
stones between tide-marks, a large part of their skin being 
frequently coated with small grains of sand. 
In connection with my contention that the vibrating fin is 
not purely and simply a lure, it is important to notice that 
the food of the reckling consists of crustaceans such as 
prawns and g'ammRrids, annelids, star-fish, pycnogons, and 
even other fish. * 
The doi’sal vibrating fin is very conspicuous, and in the 
still water of an aquarium its movement may be observed at 
a distance of three to six feet. The dimensions of the fin 
naturally vary considerably in specimens of different size. In 
a, large specimen of Motella tricirrata, measuring 260 
mm. in length and 95 mm. in girth, the groove in which the 
vibrating rays are situated was 32 mm. in length, and the 
large anterior i-ay was 7 mm. long. The fin is situated a 
slig-ht distance (about 5 cm.) posterior to the head, and is 
sepaiated from the ordinary dorsal fin by about an equal 
interval. 
The vibratile fin consists of a series of comparatively small 
processes, which are almost continuously in rapid vibration, 
and anterior to these, a ray which is much longer and thicker 
than the others, and has much less power of movement. The 
individual rays are connected with one another near the base 
by a fold of skin, Avhich passes off almost at right angles, and 
by this arrangement each ray has the power of independent 
movement. 'The rays arise medially from the base of a 
groove, the sides of which are chiefly formed by the lateral 
myomeres. 
The vibration of the rays resembles the movement of cilia, 
and there is an independent motion of each, and a collective 
action of groups of rays. A sinuous wave-like vibration is 
thus produced, which drives currents of water in a latero- 
])osterior direction over the sides of the groove. The move- 
ment of the rays or processes is almost constant, although it 
