GAS GLAXUS OF SOME TELEOSTEAN FISHES. 201 



epithelial cells, also the cytoplasm in contnct with the capillai-ies 

 is darkened in the usual way. A small amount of granular 

 material is present in the bladder lumen and gland ducts just 

 external to the cells. I mu.st also mention a peculiar class of 

 corpuscles found in the blood of my specimen of Siphonosioiiia 

 typhle. These peculiar corpu.scles (PI. V. fig.. 36) possess very dense 

 cytoplasm, are about half the size of the red corpuscles, and 

 contain large nuclei. They are fairly numerous, forming roughly 

 about 1 per cent, of the total number of coipuscles. They doubt- 

 less i-epresent white corpuscles, though in my preparations they 

 to some extent resemble small rounded ganglion cells ; indeed, 

 they bear quite a strong resemblance to the large dense ganglion 

 cells so often found between the pancrea.tic a,cini, and are in con- 

 sequence very conspicuous. I have not observed such conspicuous 

 white coi'puscles in the blood of any other of my preparations. 



In Xerojihis the gas gland epithelium is folded like that of 

 Gobius niger and possesses the same features. 



Gasterosteus spinachia. 



In this Stickleback the only feature in which the " red body " 

 differs from those of the last four genera described is the splitting- 

 up of the rete mirabile into three or four bunches supplying the 

 gas gland epithelium at different levels ; instead of the initial 

 artery and vein wholly dividing up to foim a single I'ete mirabile, 

 an artery and a vein are given off from this to form a rete 

 mirabile in connection with the most anterior region of the gland 

 epithelium, another pair to form a second rete mirabile in con- 

 nection with the middle region of the gland epithelium, and, 

 finally, the initial artery and vein themselves form a third rete 

 mirabile to supply the rest of the gas gland. This condition 

 in Gasterosteus is intermediate between that described foi 

 S'i/vgnathus and that about to be described for Feristctlms. In 

 all other respects the " red body " of Gasterosteus I'esembles the 

 Syngnathus type. 



Peristethus cataphracxus {Peristedion catapuractusi 



C. v.). 



The " red body " of Peristethus is star-shaped (PI. Y. fig. 37), 

 owing to the fact that the artery and vein which supply the glan- 

 dular epithelium, when arriving at the centre of the star-shaped 

 " red body,'' break up each into ten vessels. The score of vessels 

 thus formed sort themselves out into pairs of vessels, each pair 

 consisting of an artery and a vein. These pairs radiate out from 

 the point of subdivision of the original artery and vein like the 

 spokes of a wheel and give rise to ten elongated retia mirabilia in 

 the manner shown in text-fig. 57. Each rete mirabile supplies a 

 radially-disposed tract of glandular epithelium developed as usual 

 from the innermost cellular layer of the bladder wall. The capil- 

 lai-ies of each rete mirabile coalesce to a certain extent to form 

 lai-ger vessels before supplying the gas gland (not indicated in 



