28 



THE ELASMOBRANCH FISHES 



Gland Cells 



The integumentary beaker, or gland cell, as such (g.c, fig. 29) is produced 

 entirely from the epidermis. In sections taken through the body of the em- 

 bryo at different levels it is observed that these cells are distributed over the 

 entire surface, with but few exceptions, like the cornea of the eye. They may 

 likewise be found in the integument lining the buccal cavity (g.c, fig. 26) and 

 the cloaca, these cavities being formed as invaginations from the surface. The 

 first indication of the origin of such a gland cell is seen in the enlargement of 



a cell derivative of the basal layer. 

 This cell migrates through the inter- 

 mediate layers to the surface as do 

 the superficial cells, but instead of 

 l)econiing flattened, as do the super- 

 ficial cells, it becomes vesicular and 

 reaches an enormous size. When it 

 gains the surface a lumen forms, 

 through which the gland pours out 

 its product of excretion. 



Glaxds of Claspers 



In addition to the gland cells of 

 the type just described there are in 

 males of the Elasmobranchs numer- 

 ous gland cells which are derived 

 from the epidermis and which sink 

 in at the base of the claspers. Such a 

 gland in Sqiiatina if examined under 

 the microscope is seen to be essentially a series of enlarged goblet cells. In 

 other forms as has been shown by Leigh-Sharpe (1920-21) the gland may fill 

 up the siphon (Lamna) or it may be in only a part of its wall. In Raia circu- 

 laris (fig. 31) the gland has been compared to a date stone, bilobed in appear- 

 ance with a longitudinal groove running its entire length. Into the groove the 

 papillae open to drain the different components of the gland. 



Fig. 31. Transverse section through siphon 

 sac (s.s.), Haia circularis, to show clasper 

 gland. (From Leigh-Sharpe.) 



e.g., clasper gland; cm., circular muscle; 

 l.m., longitudinal muscle ; p., papilla from 

 gland ; s.w., siphon wall. 



Poison Glands of Sting Ray 



Goblet or mucous cells which in the sting ray, Urolophus, are present in great 

 numbers at the root of and just under the sting, form what some believe to be 

 a poison gland (p.gl., fig. 32). It is evident that these would secrete an abun- 

 dant supply of mucus which might pass along the ventral groove into the 

 wound made by the sting. It is doubtful, however, that this mucus is more 

 toxic than is the acrid mucus of other glands. 



