322 



FISHES 



by several transverse anastomoses (Fig. 190). In the region of 



the heart each posterior 

 cardinal joins the corre- 

 sponding anterior cardinal 

 to form a short but wide 

 Cuvierian duct, which 

 finally opens into the 

 sinus venosus. 



A subintestinal vein 

 is present in the embryo 

 (e.g. Lepidosteus, Acipenser, 

 and some Teleosts), 1 but 

 in the adult Teleostome 

 its precaudal section is 

 usually absorbed, or at 

 all events ceases to be 

 recognisable except, per- 

 haps, as one of the minor 

 tributaries of the hepatic 

 portal vein. 2 



The hepatic portal vein 

 is formed as in Elasmo- 

 branchs, but in different 

 Teleostomi it may also 

 receive the veins from 

 the pyloric caeca, from a 

 portion of the air-bladder, 



. 190. Venous system of a Teleost (diagram- the gonads, and, as pre- 

 matic). A, Auricle ; ab.v, vein from the air- . .. . 



bladder ; a.c, anterior cardinal ; c.d, Cuvierian VlOUSly mentioned, a tri- 

 butary from the caudal 

 vein. There are usually 

 two hepatic veins open- 

 ing into the sinus venosus, 

 and generally of equal 

 size (Fig. 190). 

 Most of the veins from the air-bladder join the hepatic portal 



rp.c. 



c.v.- 



FIG. 



duct ; c.p.c, transverse anastomoses between the 

 two posterior cardinals ; c.v, caudal vein ; h.v, 

 hepatic vein ; i.j, inferior jugular ; &,kidney ; I, 

 liver ; p.c, left posterior cardinal ; p.v, hepatic 

 portal vein ; r.p.c, right posterior cardinal : r.p.v, 

 renal portal vein ; sc.v,, subclavian vein ; sg.v, 

 segmental vein ; sp,v, spermatic vein ; s.v, sinus 

 venosus. 



1 Balfour, Comparative Embryology, London, ii. 1881, pp. 66, 91, and 96. 



2 A subintestinal vein is also present in adult Holocephali (e.g. Callorhynchus 

 antarcticus), T. Jeffery Parker, op. cit. p. 706. The persistence of this vein in 

 adult Fishes is associated with, the presence of a well-developed spiral valve. 



