DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS 1 23 



ments of an arch. Throughout its course it collects a rather 

 coarse network of capillaries from the filaments, which is in 

 direct communication Avith what is designated as the branchial 

 arch lymphatic trunk, and further this network on the arch is 

 in connection with a very fine and more superficial network, 

 which so far as could be learned had no connections with the 

 corresponding arteries. These branchial arch trunks terminate 

 dorsad either in the common branchial trunk or in the ventral 

 fork of the cephalic canal, while the main branchial trunks in 

 Polyodon discharge themselves ventrad in the inferior jugular 

 and dorsad in the cephalic canal and the hyo-opercularis sinus. 



A comparative study of the cephalic sinuses in this group ap- 

 parently does not throw much light on the phylogeny of the 

 lymphatic system. Polyodon^ the most primitive member of this 

 series, has a cephalic sinus, which in position and connections 

 resembles a similar reservoir in Amia and Sahno, while the 

 cephalic sinus of Lcfisosteits is more closely allied to a like 

 sinus in Scorpcenichthys and other Teleosts. This reservoir in 

 Polyodon is situated just mesad of the supraclavicle. It re- 

 ceives the great cephalic canal from in front which drains the 

 entire head region, the lateral lymphatic trunk from the rear, 

 and emits itself ventrad into the jugular vein. With Lept'sos- 

 teusy especially L. osseus, this reservoir is hardly deserving the 

 term sinus. It is far cephalad of its position in Polyodon^ and 

 as in ScorpcBuichthys, lies about opposite the auditory capsule. 

 From the rear it receives the hyo-opercularis and branchial 

 sinuses. The latter is in connection with a series of sinuses that 

 surround the branchial cavity and gather the subcutaneous ves- 

 sels from the remainder of the body, and about opposite the 

 cerebellum the cephalic sinus discharges itself mesad into the 

 jugular vein. 



"With LefisosteiLS the first in the chain of sinuses encircling 

 the branchial cavity to connect anteriorly with the cephalic sinus 

 is the branchial sinus. It lies between the branchial levator 

 muscles and the skull, and collects the first three branchial 

 trunks, the left branchial sinus receiving the dorsal lymphatic 

 trunk. Posteriorly each branchial sinus is in connection with a 

 spacious occipital sinus, which collects the lateral trunk from 



