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SENSE ORGANS OF AMIURUS. |: 267 
in the pike, but perhaps more closely resemble the structures which, 
in Lota, communicate with the outside by scattered pores. The 
structures to which I refer open by slit-like apertures very different 
in character from the ordinary pores. It is only in the fresh skin that 
they can be readily detected, and then it is owing to the deficiency of 
pigment in the wall of the slit similar to that which occurs in the 
mouth of the pore, that they stand off from the rest of the skin. In 
size they vary considerably. Some are larger, others much shorter 
than the pores, but all of them are very much narrower. The 
most easily recognized are those which form a sort of accessory lateral 
line stretehing obliquely downwards and backwards from the upper 
angle of the gill-slit. They are accompanied and probably supplied 
by a distinct branch of the Ramus lateralis vayi, which runs along the 
line of junction of the lateral and ventral musculature, but another 
very distinct row is to be found almost parallel to the praeopercular 
mucous canal, running down over the W/. adductor mandibule. Both 
of these are indicated by the dotted lines on Fig. 6. Again, in front 
of the dorsal fin similar slits occur, several very distinct behind the 
occipital pores, others less so, disposed transversely to the long axis 
of the body. 
I have no preparations of the adult skin which pass through these 
structures, but in a series through a young fish of two inches in 
length, made for a different purpose, I find certain detached flask- 
like sacs traceable through three or four sections, which communi- 
cate freely with the outside by apertures which are, no doubt, the 
above-mentioned slits. These sacs appear to be irregularly scattered, 
at any rate, as Leydig observes in relation to the pike it would be a 
work of some labour to map them out, but although often far re- 
moved in the trunk from the lateral canals, they appear to be always 
grouped near these in the head. They are especially numerous in 
the neighbourhood of the nerve-hillocks, and are thus found especi- 
ally on the snout, below the eyes, on the cheeks and in the occipital 
region. I recognize the same structures also in the much younger 
forms whence Fig. 7 is taken, and as well in the one series as in the 
other, the difference between these sacs and the end-buds is very 
striking. Although the central-cells of the end-bud may be retracted, 
as noted above, so as to form a little recess in the mouth of the 
‘beaker,’ the whole organ does not extend down to the corium but 
is lodged on a papilla extending half-way up through the epidermis, 
20 
