254 Transactions of the Boyal Society of South Africa. 
(internal) pharyngeal grooves are thus drained by the external jugular and 
the precaval veins. 
The anterior veins are thus the same in the tadpole as in the adult, but 
I now find that the labelling of Fig. 5 of my previous paper (already 
quoted) is incorrect ; the veins EJ should be lingual, IJ should be 
external jugular, and SS internal jugular; the brachial and cutaneous of 
the adult are new developments. 
There are pulmonary veins opening together, but apart from the other 
veins, into the imperfectly divided auricle at a very early stage of 
development. 
There are no cuvierian ducts in the sense of ducts into which both 
precavals and postcavals open. The blood from the tail is carried by a 
single caudal vein (CaV Fig. 8) to the meso-nephridia ; in the latter it 
breaks up into smaller vessels which unite again anteriorly to form the 
postcaval vein. The homologies of the posterior veins of vertebrates are 
still very obscure, and although it is, as a rule, undesirable to build a 
theory on observations on a single species, yet in view of the absence of 
any generally accepted theory another view-point cannot but be welcome. 
Bridge " splits up the original sub-intestinal vein into a postanal portion 
(the caudal vein), a posthepatic portion (the internal intestinal of 
Elasmobranchs : the anterior abdominal of Dipnoids : the hepatic portal 
of Teleosteans), and the prehepatic portion (the hepatic veins with sinus 
venous and auricle). The posterior cardinal veins Bridge takes to be a 
new development. 
That the caudal vein is not a portion of the original sub-intestinal 
should, I think, be disproved by the following considerations : — 
1. In the lowest forms such as Amphioxus it cannot be a median 
backward prolongation of the sub-intestinal, for the anus would be in 
the way. 
2. Bridge apparently supports his view on the structure of the highly 
specialized Teleosteans (see his diagram, p. 322), whereas in the Elasmo- 
branchs which, as he says, "exhibit a more primitive condition of the 
venous system in certain features than is the case in any other group," 
there is no connection between the caudal vein and the internal intestinal. 
Neither is there such a connection in Dipnoids. 
3. Teleostean embryos have the caudal vein joined to the precavals. 
Neither is it certain that the internal intestinal or anterior abdominal 
represents the posthepatic portion of the sub-intestinal for the relation 
of the postcaval to the posterior cardinals and to the internal intestinal 
is not quite clear. In Elasmobranchs the posterior cardinals are joined 
posteriorly in a way to suggest a postcaval ; in Teleosteans only the one 
posterior cardinal suggests a postcaval ; and in Dipnoi the similarity of 
* Bridge, " Cambridge Natural History," Fishes. 
