Charles F. W. McClure - 167 
addition to this, the subcardinal veins persist in the adult as the left 
suprarenal and genital veins. 
The veins which Lewis and Miller have described under the name of 
“ subeardinals ” were, so far as known to the writer, first described in 
the embryos of birds and mammals by Hochstetter, 88 and 93, who re- 
garded them as the homologues of the revehent veins of the Wolffian 
bodies in reptiles. In tracing their subsequent development, however, 
Hochstetter found that they disappeared for the most part, and were 
represented in the adult by only the left suprarenal and possibly the 
genital veins in the chick, and by the left suprarenal vein in the rabbit. 
In addition to the mammals, Lewis, 04, has also recently described the 
subcardinal veins as met with in the selachians (Torpedo and Acanthias), 
amphibians (Necturus) and reptiles (Lacerta) and, in the writer’s opin- 
ion, has correctly interpreted the role which these veins play in the 
formation of the adult renal portal system. He states that in Torpedo 
and Acanthias, after fusing to form the genital sinus, the subcardinals 
make connections anteriorly with the cranial ends of the postcardinals 
and with the latter form the revehent veins of the adult renal portal 
“system. In Necturus the subeardinals fuse to form an unpaired vessel, 
which, after making connections with the hepatic circulation, constitutes 
the greater portion of the posteava. In Lacerta the subcardinals also 
form a large part of the postcava, although the fusion between the two 
veins is less complete here than in Necturus (Lewis). 
Lewis, so far as known to the writer, was the first investigator to in- 
terpret the development of the venous system of the selachians and am- 
phibians in the terms of the subcardinal veins, and, although I feel con- 
fident his interpretations are correct, at the same time a more thorough 
investigation of the amphibia is to be desired before any definite conclu- 
sion can be established. In reptiles, however, Hochstetter, and, more re- 
cently, my pupil Stromsten, 05, have conclusively shown that the veins 
which form a large portion of the postcava are the homologues of the 
so-called subcardinal veins of birds and mammals. To what extent the 
subeardinal veins may be developed in the embryos of vertebrates other 
than those mentioned above, it is impossible to state without further 
investigation. From our present knowledge of the subcardinals, how- 
ever, it is evident that they possess so great a morphological significance 
in certain vertebrates, that any interpretation of the vertebrate venous 
system must necessarily be incomplete without, at least, taking into con- 
sideration the presence or absence of these veins. 
There can be no doubt as to the morphological significance of the sub- 
cardinal veins; that their development is -primarily correlated with the 
