GAS GLANDS OF SOME TELEOSTEAN FISHES. 203 



aspect, appears as an elongated sac, the vcnti-al wall of which is 

 very muscular in the median line posteriorly. At the sides of this 

 muscuhir posterior median portion of the bladder wmII there are 

 to be seen two ]'ed streaks, which are the lateiul divisions of the 

 " red body" (PI. VI. fig. 42). In a series of transverse sections it 

 can be seen that the cavity of the bladder has a peculiar conform- 

 ation* ; anteriorly the bladder cavity consists of two laterally-pliiced 

 channels, which end blindly anteriorly and proceed posteriorly 

 over a distance equal to about one-third the length of the bladder 

 when each divides into two ; these four chaniiels thus formed then 

 extend to about midway in the length of the bladder, when the 

 two inner channels coalesce to form a wide median cluuuber, 

 which, with the tAvo external channels, extends to the posterior ex- 

 tremity of the bladder (PI. Y. fig. 43). It will be observed in figure 

 43 that two great median bands of muscle (M.R.) are developed 

 in the ventral wall of the posterior half of the bladder, and this 

 explains why it is that only the lateral "red bodies" are seen 

 when the bladder is viewed from the ventral aspect (fig. 43). 

 Also shown in this figure are the two laterally-placed sti'ands (S) 

 of nerve-fibres developed in connection with the two muscle- 

 bands. 



The epithelium of the gas gland is folded in the manner cha- 

 ractei-istic of this type of " red body," but in Triyla it is more 

 folded than in previous examples (PI. VI. fig. 44), the primary 

 folds bearing small lateral folds. In some places the depth of the 

 folding is increased as in Syngnathus. The cells are of moderate 

 size and columnar in form. The rete mirabile is divided u[) into 

 capillary tufts, i. e. there are numerous small retia mirabilia which 

 supply the epithelium at intervals in its course ; in other words, 

 pairs of vessels are given off at intervals from the bladdei' ai-tery 

 and vein, each pair consisting of an artery and a vein and forming 

 a rete mirabile to supply a certain area of gas gland. 



TrigLiA gurnardus. 



Concerning the gas gland epithelium of this species, see p. 207, 

 below, 



Smaris maurii, Smaris vulgaris. 



The " red body " of Smaris vidgaris has the macroscopic appear- 

 ance shown in figure 45 (PI. VI.). Figure 46 (PL V.) represents 

 diagi'ammatically a transverse section aci'oss the anterior end of 

 the " red body," the primary artery and vein entering at the 

 centre of the oval mass. 



Concerning the character of the gas gland epithelium of these 

 two species (PI. VI. fig. 47), see p. 207, below. 



Previoihsly described " Red Bodies " of the Syngnathus l^yj^e. 



The glandular epithelia of the "red bodies" of Gohins capilo, 

 Trigla gurnardiis (see my description below), and Gasterosteus 



* Sue descriptiun in Mlliiu-Edwardb (49). 



