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 (i, 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 aequire 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 fi 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 indifferent 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 



