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ganglion is always associated with the trigeminus, except 
in the Physostomi, where there are no ganglia in front of 
the vagus. This is what we should expect, as the cranial 
sympathetic appears for the first time in the bony fishes, 
and the Physostomi are undoubtedly a primitive group 
of Teleosts. 
F.—THE SENSE ORGANS. 
1.—Tue System or LATERAL SENSE ORGANS 
oR SENSORY CANALS. 
(Figs. 23 and 29.) 
The obvious line seen at the side of the body in most 
Fishes, including the Plaice, and known as the lateral 
line (Seitencanal of German authors), is in our type a 
long tube or lateral canal, protected by a row of modified 
scales (lateral line ossicles), and opening on to the surface 
by pores at more or less regular intervals. These pores 
may open directly into the canal or they may do so by the 
intermediation of a little tubule. At first the only sub- 
stance found in such a canal as this was a quantity of a 
jelly-like mucus, and hence these canals were called 
mucous canals, and were supposed to secrete the mucus 
on the surface of the body. The discovery, however, that 
‘they contained large sense organs, one of which usually 
occurred between two succeeding surface pores, and that. 
the mucus was only of minor importance, and developed 
by the numerous goblet cells in the lateral canal itself to 
enable the sense organs to perform their function, and also 
that the mucus in the lateral canal was of quite a different 
character to that occurring on the surface of the body, 
conclusively proved that these lateral canals constituted a 
sensory structure and could not therefore be called mucous 
