436 MR. C. H. 0 DONOGHUE ON THE 
satisfactory. Although the general disposition of the main vessels 
in Mustelus antarcticus is somewhat similar to that in Seylliwm 
canicula, the two species differ considerably in detail in the veins 
and, as might be expected from the modification of form undergone 
by the skates, the veins of these are markedly different from those 
in the dogfish. In view of this and of the fact that Sceyllium 
is frequently used as a type in the laboratory, the venous 
system of the latter appears worthy of description. 
An account of the arteries, on the other hand, is not so 
necessary, as they do not vary nearly so markedly from those 
described in other Elasmobranchs as do the veins and, moreover, 
they are much more satisfactorily dealt with in text-books. 
The animals were investigated by means of injection and series 
of transverse sections through embryos of 37 and 56 mm. length, 
and serial sections through a frozen adult were also examined 
in order to check certain points. The injection-fluids used 
were the gelatine mass, recommended by Tandler (15) for the 
finer details, and the starch mass advised by Kingsley (6) for 
the larger vessels. In a previous communication on the blood- 
vessels of the grass-snake (7) I recommended using a mixture of 
the solid matter that settles to the bottom of the starch mixture 
with about twice its volume of gelatine, and I have now found 
that an almost identical mixture was suggested for the blood- 
vessels of the skate some time previously by Rand (18). 
Perhaps the most striking feature of the venous system of 
Scyllium is the dilatation of the vessels to form sinuses. These 
sinuses render the injection of the system as a whole impractical, 
and the indefinite nature of their walls makes it extremely 
difficult to trace their exact course and extent with certainty 
or to locate the points of entry of the smaller tributaries. 
For the sake of ready reference the names of the vessels 
adopted by Parker have been used as far as_ possible, and 
wherever alteration has been made Parker’s terminology is also 
given. 
II. DEVELOPMENT’. 
The pre-cardiac part of the venous system at a fairly late 
stage of development is represented by the anterior cardinal 
vein. This is morphologically composed of two sections: from 
the ear back to the ductus Cuvieri it is the persistent anterior 
cardinal, but the front part of this vessel has been replaced by 
the lateral cephalic vein. It is convenient, however, to speak 
of the whole trunk in the adult as the anterior cardinal sinus. 
In the adult an inferior jugular vein is developed on each side 
in addition to the foregoing sinus. 
In the post-cardiac portion two distinct systems are to be 
recognised : first, the posterior cardinal veins, and second, the 
sub-intestinal vein. The posterior end of the first forms a loop 
around the growing mesonephroi, and later the median portions 
of the two loops fuse to constitute the inter-renal section of the 
