428 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
backwards to the lateral walls of the internal cavity of the cerebel- 
lum. The second supplies a pair of arteries to the twbercula acoustica 
and a second pair which divide before entering the /obi trigemini. 
The third gives off a set of four branches to the parts behind the 
cerebellum. 
The median stem also gives a pair of lateral branches to the audi- 
tory labyrinth. 
The artery from each half of the first branchial arch turns forward 
and passes through a foramen in the hypohyal, and then turns back- 
wards and outwards along a groove on the dorso-lateral margin of the 
ceratohyal. On reaching the epihyal it divides itself into three 
branches. A large branch returns along the mandible supplying it 
and the appended barblets ; a second branch crosses the outer surface 
of the epihyal to supply the branchiostegal rays ; and a third pass- 
ing onward to the attachment of the operculum distributes itself 
upon it. 
The arteries from the other three pairs cf arches show considerable’ 
irregularity in anastomosing and giving off independent branches, 
but the tendency is to unite in a large median stem between the: 
pericardium and the copule of the arches. From this hyoidean 
plexus all the surrounding parts are supplied. The coronary artery 
divides into two stems, a dorsal and ventral, which enter the wall of 
the bulbus at the point of attachment of the pericardial membrane. 
The thyroid artery is usually a branch of the coronary. 
A pair of large arteries to the hyopectorales and another pair more: 
posterior to the pharyngo-claviculares are the more important stems 
to the muscles. 
All the arteries of the trunk and tail, except those to the organs. 
within the body cavity, and those to superficial parts of the head, end 
in a rich capillary network in the subcutaneous connective tissue of 
the skin. The ability shown by these fishes to live for a considera- 
ble time out of water is no doubt due to aeration of the blood in 
these capillaries while the mouth and gill-cavity are kept closed. If 
the skin be moistened artificially this period can be greatly prolonged. 
THE VENOUS SYSTEM. 
The vena caudalis arises in the tail-fin, usually by two vessels of 
unequal size having the same course as the arteries. It runs for- 
ward in the hzmal canal beneath and in contact with the caudal 
