BL001)-VASCULy\R SYST1'>M OF THE LORICATI 77 



terior mesenteric artery was not observed ; possibly, however, it 

 was not injected. The posterior spermatic proper breaks up 

 into numerous branches, which run along the posterior surface 

 of the ovaries or penetrate the testes. The most posterior branch 

 of the third spermatic artery is destined to supply the common 

 oviduct or spermduct and sends off the anterior urinary 

 bladder artery to the bladder. The posterior urinary bladder 

 artery (PI. I, figs, i and lo ; Ur.B.A.) or the urinary bladder 

 artery proper arises from the aorta directly behind the kidney, 

 and in the specimen from which fig. lo was drawn, a renal 

 artery was given off to the kidney. In addition to supplying 

 the urinary bladder this vessel usually sends off a branch to the 

 great lateral muscle. It is probably a modified haemal artery, 

 (c) Comparisons of Hexagr amnios ^ Scorpcenichthys and Sebas- 

 todcs. — In these 3 different genera there is not nearly as much 

 variation in the distribution of the dorsal aorta as there is in the 

 distribution of the cardinal veins. Hcxagrammos is identical 

 with Ophiodon. In ScorpivnicJithys there are only 2 spermatic 

 arteries, but what has been designated as the urinary bladder 

 artery (PI. IV, fig. 29 ; Ur.Bl.A.) arises much farther cephalad 

 than the corresponding vessel in Ophiodon, and may in part be 

 homologous to the posterior spermatic artery of Ophiodon^ 

 except that it does not supply the reproductive organs ; running 

 along the dorso-caudal surface of the kidney it passes between 

 the suprarenal bodies and sends off a branch to each of them. 

 (It will be noticed that the suprarenal glands are located much 

 further 'dorsad on the kidney than they are in Ophiodon.). 

 Then passing ventrad the urinary bladder artery passes behind 

 the posterior mesenteric vein to supply the posterior part of the 

 urinary bladder, and usually it is continued still farther ventrad 

 to supply the rectum. In Sebastodes several changes are intro- 

 duced, which are caused by the presence of the air-bladder and 

 anterior spermatic arteries. Where the anterior spermatic artery 

 is given off in Ophiodon^ Hexagrammos and Scoi'pcBuichthys a 

 similar vessel arises from the aorta in Sebastodes; this vessel, 

 however, is destined to supply the air-bladder and is designated 

 as the posterior air-bladder artery (PL IV, fig. 31 ; P.A.Bl.A.). 

 In passing over the left side of the kidney it gives off several 



