A3 
to be exclusively confined to one of the parties, the Pilot- 
Jish, and to be neither more nor less than a parasitical attach- 
ment, founded on the frequent opportunities it enjoys of 
picking up the small scraps scattered about by its ravenous 
associate in the act of devouring its prey. 
* The Sucking-fishes (Echeneis Remora) are not so constant 
in their attendance on the shark as the pilot-fish, but when 
they do accompany it, I have no doubt they are urged by 
the same selfish motive. When fatigued with its own exer- 
tions, the Remora fixes itself on the shark, and is carried 
along without any further effort than that of sticking fast. 
The instrument of adhesion is a flat process covering the 
crown of the head, and surrounded with a fleshy border. It 
consists of seventeen transverse bony plates, overlapping 
each other, and divided by a longitudinal septum. When 
this instrument is to be put to use, the Remora applies the 
crown of its head to the skin of the shark, then raises the 
bony plates on their edge, like the plates of a Venetian blind, 
while the fleshy border adhering firmly prevents any com- 
munication from without, and thus a vacuum is formed 
which it requires a strong force to overcome. The outer 
edge of the plates is rough like a file, to prevent their sliding 
along the object against which they are applied. "The ordi- 
nary colour of the Remora is purple, but it possesses the 
faculty of changing it suddenly from that to pulberhite, 
This I had an opportunity of rep y « dn 
two individuals we caught, which I dins dive for a ebole 
day in a bucket of water. 
* In the organization of this singular little. fish, we have 
to admire the wisdom of nature in the adaptation of means 
to ends. Why the Remora should be furnished with the 
means of transporting itself by foreign assistance, is a ques- 
tion which no one, so far as I know, has attempted. to solve. 
But having been so furnished, we can easily perceive that 
the instrument has been placed on the only part of its whole 
body where it could perform its functions with effect. The 
Cyclopteri are provided with an apparatus intended for a 
similar purpose. In them it is situated on the breast, but as 
