014 PROCEEDINGS OF THE AMERICAN ACADEMY. 



and therefore may lead to inuch confusion. In the ventral region, 

 where the tissues are transparent, connective-tissue threads may be 

 readily discerned in gold-chloride preparations, weaving about the 

 nerves, and running out from them in A^arious directions like guy- 

 ropes. These threads thus furnish an excellent pitfall for the observer. 

 Where exceedingly fine nerve branchlets and connective-tissue tlu'eads 

 are associated with each other, one may well hesitate to decide be- 

 tween them. The bodies (c) connected with the fine tlireadlets shown 

 in Figure 24, all lie in the same plane with the threadlets, whereas the 

 epithelial cells and special cells (g) are more superficial, being imme- 

 diately exterior to these threadlets. The latter may be terminal nerve 

 branches, interweaving at the bases of the epithelial cells, and sending 

 branches between them, but e^'idence furnished by some other method 

 is needed for corroboration. If these threadlets are nerves, they are 

 probably connected with the finer plexus noted in methylene-blue 

 preparations. 



The special cells (g) previously mentioned are shown in Figure 42 

 (PL 7) under greater magnification. This figure illustrates the exter- 

 nal surface of skin overlying the side muscles near the dorsal fin. 

 This preparation was impregnated with gold chloride after Ranvier's 

 method. In preparations of this kind the ordinary epithelial cells 

 are light purple in color, while certain differentiated cells lying be- 

 tween them appear red, are somewhat smaller, and are oval or circular 

 on their external faces instead of polygonal. One or two slightly 

 modified epithelial cells (s) are usually associated with each special 

 cell. These accompanying cells assume a darker purple color than the 

 ordinary epithelial cells. The special cells (g) and the modified 

 epithelial cells (s) were both present in certain methylene-blue prepa- 

 i-ations, distributed in the rostrum and anterior portion of the body as 

 far as nerve XVI. Unfortunately, favorable preparations of the skin 

 of more posterior portions of the body were lacking. In these methy- 

 lene-blue preparations the special cells assume a dark blue color, 

 while the modified epithelial cells are only slightly darker colored than 

 the ordinary epithelial cells, and present a granular appearance. 



Changes in focus show that the diameter of these special cells is 

 slightly less at the surface than at a short distance toward the interior. 

 The most striking feature, however, of these cells is a rather long, 

 stiff hair-like structure attached to the outer surface of each cell. 

 In gold-chloride preparations this hair-like structure is colored black, 

 or a very dark purple. In methylene-blue impregnations it appears 

 dark blue. As shown in Figure 42 (PI. 7), this "hair" is thicker at its 



