1922.] S. L. Hora : Fish of Mountain Torrents. 51 



The structure of the tuberculated region, on the other hand, 

 is totally different. In a vertical section (fig. 13) of the fringed 

 portion of the anterior labial fold, the superficial epidermal layer 

 covering a tubercle is modified into spines (s). It is perhaps 

 significant that I have not been able to find any nuclei in the 

 spines; the spines are, otherwise, shorter, thicker and stouter 

 than those described in Bhavania annandalei. On examining a 

 large number of sections of this region aud of the free tuberculated 

 borders of the disc, I have observed that the spine is formed as a 

 prolongation of the outer cell-wall of the superficial epidermal 

 layer. Below the spinous layer, there are several tiers of polygonal 

 cells (ep.d.) which are vacuolated. In the basal region the cell- 

 limits are not well marked and the nuclei stand out prominently 

 with haematoxylin stain. In some cells the nuclei are surrounded 

 by a whitish halo. The dermis (d) consists of a compact connec- 

 tive tissue, with a large number of nuclei scattered just below the 

 epidermis. The cell-boundaries in this region are not well-defined. 



In the region of the posterior labial fold and also in that of 

 the free border of the disc, the tubercles are provided with a 

 dermal plug. The dermis consists of a large number of branched 

 irregular cells, forming a primitive type of connective tissue. 



The structure of the tuberculated region in Garra differs from 

 that of the integument and of the central callous portion of the 

 disc in the following points : — 



(i) The gland-cells are absent. 



(ii) The " clavate cells " are absent. 



(iii) The superficial epithelial layer of cells is modified into 

 spines which do not possess any nuclei. 



(iv) The adipose tissue is totally absent, and the dermis, 

 therefore, presents a compact, solid structure. 



In the order Siluroidea the modification of the skin to form an 

 adhesive apparatus is very different. It is thrown into folds and 

 ridges, which are characterized by a special structure. Any por- 

 tion of the skin may thus be modified to serve the purpose of 

 adhesion. To illustrate the structure of the adhesive apparatus 

 in Silurid fishes, I will first describe that found in Glyptostemum 

 labiatum. 



The structure of the integument found in this genus may in 

 the first place be considered. In a vertical section (fig. 14) of the 

 non-striated skin covering the dorso-lateral surface of the pectoral 

 spine, the epithelium consists of several layers of small, more or 

 less flattened and rectangular cells which possess well-marked 

 cell-walls and relatively large oval nuclei. The cells near the sur- 

 face are smaller than those immediately below them. Their out- 

 line varies considerably according to the extent to which they 

 may be packed together in a particular place. Black pigment (p) 

 is present at certain places in the tissue. Most of the central 

 space of the epithelium is occupied by a number of big " clavate 

 cells " (c), which are distributed at regular intervals and form a 

 distinct layer of their own. They are fairly well developed and 



