Just back of the spiracle the anterior cardinal receives the _hyoidean vein_, which passes ventrad along the base of the first demibranch and unites with the hyoidean of the opposite side. Ventrally, it also communicates with the inferior jugular vein. The principal veins of the body have now been dissected with the exception of the _hepatic portal vein_, which it is better to trace after the arteries of the digestive tract have been studied. THE EFFERENT BRANCHIAL ARTERIES AND DORSAL AORTA. Commencing at the mouth, cut through the floor of the pharynx close to the left side of the ventral aorta and the heart. The cut should leave the gill arches uninjured, and may be continued into the oesophagus. Examine the interior of the mouth and pharynx, observing particularly the form and arrangement of the teeth, the spiracular and branchial clefts, the gill rakers, and the character of the mucous coat of the pharynx. Remove the skin from the roof of the pharynx. This exposes four pairs of _efferent branchial arteries_ bringing blood from the gills and uniting in pairs to form the _dorsal aorta_. Follow each vessel of the left side out to its gill-cleft. At the dorsal end of the gill-cleft it divides into a large posterior and small anterior branch. These respectively pass along the posterior and anterior demibranchs of the gill pouch, receiving fine branches from the gill lamellae, and finally unite again at the ventral end of the gill pouch. Thus a complete loop is formed around the branchial cleft. The posterior branch of each efferent artery and the anterior branch of the succeeding one are united by several short vessels. The efferent artery of the last demibranch possesses only these connections with the branch next anterior to it, and none with the aorta directly. From the ventral ends of the efferent loops small vessels pass toward the midline to unite with a longitudinal artery, the _hypobranchial artery_, which will be traced farther a little later in the dissection. In Eugaleus the dorsal aorta extends forward beyond the union of the first pair of efferent branchials and then divides into small right and left branches which pass forward and outward to unite with the common carotid arteries. A _common carotid artery_ leaves the dorsal end of each anterior efferent branchial loop, passing forward and inward. At the level of the spiracles it divides into _external_ and _internal carotids_; the internal carotid unites with its fellow of the opposite side and enters the skull. The external carotid arteries run outward and forward around the eyes and are distributed to the regions of the mandible and snout. Do not, at present, trace them beyond the posterior edge of the eye.