424 C. H. DANFORTH 



gives rise only to nutrient branches, passes over the posterior 

 face of the muscle connecting the cerato- and epi-branchial 

 cartilages and across the epibranchial directly to the pharynx. 

 The other part (figs. 9, 10), which gives rise to both filamentar 

 and nutrient branches, follows the dorsal edge of the cartilage 

 and supplies the filaments of the anterior hemibranch. It goes 

 anterior to the attachment of the m. levator arcus branchialis 

 and reunites with the vessel from which it arose. Allis infers 

 from Allen's drawings that the loop thus formed is interrupted 

 medially in the adult, but such is not always the case, for in 

 all the specimens which were examined by the writer the loop 

 was found to be complete as shown in the figures. 



Although the filaments of each of the first three posterior 

 hemibranchs are practically in a continuous line above and below 

 with those of the next succeeding anterior hemibranchs, the eby 

 completely surrounding the clefts with filaments, I have been 

 unable by gross methods to find any connection at this point 

 between the arteries of the successive gills. Allis, however, 

 finds an indirect connection between the arteries of the third 

 and fourth gills. 



THE HYPOBRANCHIAL ARTERIES 



In all groups of fishes a system of hypobranchial arteries is 

 of constant occurrence, but the details of arrangement are rather 

 variable. These arteries are derived from anastomoses between 

 recurrent vessels which arise from the efferent arteries within 

 the gills. Frequently secondary longitudinal trunks are formed 

 which from their position T. J. Parker ('84, '86) has designated 

 the lateral and median hypobranchials. Their transverse con- 

 nections he calls commissural arteries. That author, it may 

 be observed, regarded the whole' system as derived from the 

 subclavian artery because in the sharks, with which he worked, 

 there is a connection between the two. The connection with 

 the gill arteries he thought to be secondary. This view, how- 

 ever, has received little subsequent support and is not now 

 generally maintained. G. H. Parker and F. K. Davis ('99) 



