SENSE ORGANS OF AMIURUS. 253 
the cells proportionately large. In preparations where the elements 
have “been dissociated in Miiller’s fluid, the cells are much more 
irregular than they appear in sections ; and are further rough with 
the protoplasmic projections, ‘ intercellular bridges,’ which establish 
connection with their neighbours. In the lower layers they gradu- 
ally become somewhat changed in outline until they acquire the 
form of 
(c) Spindle-shaped Cells.—These form a considerable part of the 
thickness of the epidermis. In length they may measure as much as 
35 w, their nuclei, from 8-9, occupying the greater part of the 
breadth of the cell. They form a transition from the more super- 
ficial layers to 
(d) The Palisade Cells, which, however, may be twice as long, 
and rest with a broad base on the surface of the corium. Under 
certain changes produced by reagents, the palisade cells are sepa- 
rated, to some extent, from the corium, being still connected with 
it by protoplasmic filaments. The appearance is then produced of a 
space separating the two layers and only traversed by the filaments 
aforesaid. } ; 
(e) Mucus-Cells.—These are common to all Pisces, and produce 
the slime which covers the surface of the skin, and which also invests 
the cavity of the mouth. They appear to be distributed equally over 
the skin except where they are interrupted by the presence of the 
cutaneous sense-organs. Sections which have been stained in Bis- 
marck brown are unquestionably best suited to the study of these, the 
intracellular net-work taking on a ‘most characteristic and vivid 
stain. The cells are not confined to the uppermost layer of the epi- 
dermis, but are formed by the conversion of ordinary lower poly- 
gonal cells, which at first acquire a round outline distinguishing 
them from their neighbours and gradually become considerably large. 
Thus, a mucus-cell which has not yet reached the surface but is fully 
grown, may measure 20-25 in length. As the surface is approached 
the outline becomes more oval, and when the cell eventually opens 
by a distinct aperture between the ordinary epidermal cells the oval 
outline is more elongated. The intracellular network which at first 
appears to be formed of meshes equally strong in different directions 
then takes on a different character. Its elements are chiefly dis- 
posed longitudinally immediately after the expulsion of the little 
plug of mucin which also stains in Bismarck brown. Then only is 
