168 



THE SPINY DOCxFISH-THE SKATE 



The 



four branchial arteries go to the gills of the first four branchial arches, 

 fifth branchial arch is without a gill. 



Notice the thyroid gland lying at the anterior end of the ventral aorta. 



Note that each end of the sinus venosus passes into a short duct of Cuvier. 

 The large posterior cardinal sinus, which extends forward dorsally from 



-%VentraI aorta 



Gills-:: 



Conus 

 arteriosus 



Fig. 56. — The Dogfish {Acanlhias, syn. Squalus). Afferent Branchial or Ventral Arterial System. 



between the kidneys, opens into the duct of Cuvier at each side. The anterior 

 cardinal sinuses, which extend from around each eye and above the gill-arches, 

 also open into the duct of Cuvier opposite the posterior cardinal sinus openings. 

 The hepatic sinus of the liver opens (two openings) into the posterior wall of the 

 sinus venosus. Slit open the sinus venosus, and pass a seeker into these sinus 

 openings. 



Note that the pericardium is a portion of the coelome or body-cavity which 

 has been separated off. It is, however, in communication with the main cavity 



