GAS GLANDS OF SOME TELEOSTEAN FISHES. 207 



the glandular epithelium is always unilaniinav and the folds always 

 clearly recognizable. My prepn.rations do not at all confirm 

 Rei.s's statement that the tabular outgrowths are so numerous nt 

 the base of the gland that they lose their lumina through mutual 

 contact, and form almost complete layers of epithelial cells. On 

 the other hand, the gas glands of some other genera which 1 have 

 examined certainly do appear to be transitional in structure 

 between the folded and massive types, viz. those of Trigla gurnar- 

 dus, Smaris maurii, and ASmaris indgaris. I may say at once 

 that in all three species, especially Triyla guriutrdus and Smaris 

 maiM'ii, the gas gland shoAvs distinct signs of being of the folded 

 type, and in the two species just mentioned the folds are quite 

 distinct and unmodified at the edges of the glands, but, on the 

 other hand, the surface of the gland is covered by a continuous 

 single layer of columnar epithelium (never present in the typical 

 folded gland) and throughout the mass of the gland the cells at 

 certain points lose their unilaminar arrangement *. In Trigla 

 gihrnardus f", and perhaps also in the other two species, the explana- 

 tion of the superficial cell-layer seems to be that at the edges of 

 the gland the unilaminar epithelium splits into two layers, the 

 upper remaining unfolded and forming the superficial cell-layer 

 and the lower becoming folded in the usual manner (text-fig. 58), 

 the folds, however, anastomosing to a considerable extent and, as 



Text-fig. 58. 



Diagram to explain the probable construction of the gas glands of 

 Trigla gurnardiis and Smaris inaurii. 



already mentioned, the cells in places becoming clustered into 

 groups more than one layer in thickness. In Smaris maurii (PI. VI. 

 fig. 47) the individual cells are larger than in Trigla gurnardus 

 and the anastomosing folds more closely packed ; here and there 

 the cells are several layers thick, but in general they are arranged 

 in single folded rows as in Trigla gurnardtts. In Smaris vulgaris 

 the epithelium has almost entirely lost its folded character, though 

 this is sometimes to be detected at the edges of the gland. Thus 

 the gas glands of these three species t are to a certain extent 



* In many massive glands the cells are often i)i places arranged in single rows, 

 and this is evidently due to the necessity (which Opi)el points out : see footnote on 

 page 208) of each cell being in contact on one side with a duct and on the other 

 with a blood vessel. 



t Coggi (25) provides a figure of the epithelium of this species showing a simple 

 folded character; the epithelium in my specimens more resembles his figure of the 

 epithelium of Ilotella mediterranea with the addition of a superficial covering- 

 layer of columnar cells. 



X And possibly those of Folyacantlnis- (Mavrnpodus) des-cribed by lleis & 

 Xusbaum (62) and MoteUa described by Coggi (25). 



