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 tubercula acoustica 

 and a second pair which divide before entering the lobi 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 dor so-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 arte lies from the other three pairs of 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 copulaa 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 haemal canal beneath and in contact with the caudal 



