260 BULLETIN OF THE 



In consequence of the uncertainty as to what vein of the adult this 

 vessel represents, I shall here digress to describe its distribution at this 

 stage. For purposes of description, I shall follow it from its point of junc- 

 tion with the cardinal vein forward towards its finer branches. Before 

 reaching the ganglion nodosum, it sends a branch dorsalward, which can 

 be traced for a short distance between the lateral wall of the cranium and 

 the ganglion. The main trunk continues forward external to the ganglion, 

 and gives off a branch which passes around the posterior end of the audi- 

 tory capsule and enters the cranium. The original vessel now passes for- 

 ward through a narrow channel left between the auditory capsule and the 

 articulating portion of the mandibular cartilage. Near the anterior end of 

 the auditory capsule it divides into two branches, one of which passes dor- 

 sal to the eyeball, accompanying in its course the ophthalmic branch of 

 the trigeminal nerve ; the other branch passes ventral to the eyeball, and 

 continues into the anterior maxillary region, following the course of the 

 canalis nasalis. The main trunk runs nearly parallel to the aortic root 

 and its prolongation, the carotid artery, the efferent branchial trunks 

 joining the aortic root by passing immediately ventral to the vessel whose 

 course I have been following. The vein evidently corresponds to the 

 one described under Stage V. of Rana (page 233, foot-note), and appears 

 to me to represent in all probability the internal jugular of Gruby ('42) 

 and of Ecker ('64-'82). 



The glomus is considerably broader and thicker than in Stage V. ; 

 but its longitudinal extent is about the same. In the middle of its 

 course its distal edge reaches across the body cavity and fuses with the 

 somatic peritoneum which covers the pronephros. The structure of the 

 organ appears to be nearly the same as in the preceding stage, but the in- 

 terior mass is so compact that one can distinguish little more than the 

 nuclei, which present quite uniform characters. Cells which are unques- 

 tionably endothelial are frequently evident along the basal surface of the 

 peritoneal layer ; they also traverse the interior of the glomus dividing 

 this space into compartments. Pigment is present both in the peritoneal 

 wall and in the interior mass. It has a scattered distribution, appearing 

 in the form of perfectly black patches. The large cells to which allusion 

 was made in Stage V. are present also in this stage. They have about 

 the same size and histological features that formerly characterized them. 

 The pronephric chamber has not changed materially from the condition 

 exhibited in Stage V. The most anterior pronephric tubules are situated 

 immediately latei*al to a diverticulum of the body cavity, which in sec- 

 tions through this region appears wholly isolated. On following the 



