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 

 Cuvieriau duct, which 

 finally opens into the 

 sinus venosus. 



A subintestinal vein 

 is present in the embryo 

 (e.g. Lepidosteiis, Acipenser, 

 and some Teleosts)/ 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.' 



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, 



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



matic). A, Auricle; ab.v, vem from the air- . ^ '^ 



bladder ; a.c, anterior cardinal ; c.d, Cuvieriau VlOUsly mentioned, a tri- 



dnct ; c.p.c, transverse anastomoses between the l-mforTr from tV,Q /.onrlol 



two posterior cardinals ; c.v, caudal vein ; h.v, ^^^^^^ ^^"^ ^^^ °^^°*1 



hepatic vein ; i.j, inferior jugular ; A-,kidney ; I, Vein. There are USUally 



liver ; ^.c left posterior cardinal; p.v, hepatic f„^ ■!,„„„*• 



portal vein ; r.pc, right posterior cardin;i ; r.p.v, ^^^ , hepatic Vems Open- 



renal portal vein ; sc.v,, subclavian vein ; sg.v, ing into the sinUS VenOSUS, 



segmental vein; sp.v, spermatic vein ; s.v, sinus j n ,. ,' 



venosus. and generally of equal 



size (Fig. 190). 

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



rj).c. 



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



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

 cmtarcticus), 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. 



