54 



Records of the Indian Museum. [Vol. XXIV, 



".v. 



s.r.c" 



not been able to determine definitely. Below the spines is a deep 

 non-cellular layer (n.c. r.) in which are scattered a number of 

 spaces (c) having a definite shape. They are almost crescentic in 

 outline and possess a short spine-like process along their convex 

 borders. The lower limit of the non-cellular region is formed by 

 a regular wavy line. In the curves of this wavy line are situated 

 a number of characteristic columnar cells. Each is provided with 

 a nucleus, a distinct, nucleolus and a small well-marked vacuole 

 (v). Between two neighbouring cells there is generally a small 

 chink-like cavity. Below these columnar cells, are a number of 

 small epithelial cells which are irregularly arranged in four to five 

 tiers. Usually they possess small, solid, deeply staining nuclei, but 

 in certain cells the nuclei are altogether absent. Beneath the 

 epithelial tissue is a loose connective tissue (c.t.) forming the 

 dermis. 



In the genus Glyptosiemum, the adhesive apparatus is sup- 

 ported by a definite tissue as has already been remarked. The 



supporting tissue (fig. 

 16) consists of a mass of 

 polyhedral cells (fig. 17) 

 which are very turgid 

 and are closety packed 

 together. The nuclei of 

 these cells are fairly 

 large and in certain 

 cases there may be more 

 than one nucleus in a 

 cell. The cells vary in 

 form and size to a 

 considerable exten t and 

 towards the base they 

 are so much pressed 

 together that the cell- 

 limits become almost 

 obliterated and the 

 nuclei become spindle- 

 shaped. The support- 

 ing tissue (s.t.c.) is sur- 

 rounded by a loose con- 

 nective tissue (c.t c). 



The structure of the 

 thoracic adhesive appa- 

 ratus of Pseudecheneis 

 sulcahis is different 

 from all the three types described above. The nuclei of the spines 

 are situated in the non-cellular region and the cell-walls in the 

 epithelial region are not well defined. In the cells of the first 

 epithelial layer, immediately below the non-celluiar region, there 

 are ill defined vacuoles. The connective tissue is not so loose and 

 is richly dotted with a large number of nuclei of various forms. 



Text-fig. 16. — Transverse section through the 

 thickened skin covering the pectoral spine in 

 Glyptosternum labiatum, x 42. 



s.t. = supporting tissue; c.r. = clavate cell re- 

 gion ; p. = pigment ; s.r. = striated region ; b.v. = 

 blood vessel ; c. = clavate cells. 



