MUSEUM OF COMPARATIVE ZOOLOGY. 233 



cranium, passing close to the median wall of the auditory vesicle and the 

 ball of the eye. 1 



There are two kinds of cells found within the capsule of the pronephros 

 concerning which I have as yet said nothing. Those which are more 

 numerous are scattered, Of circular outline and of unform size. Each has 

 in general three or four large yolk spherules, and the nuclei are rather 



1 In order to ascertain, if possible, what vein of the adult this vessel represents, it 

 vrill be necessary to describe here its condition in later stages. In the oldest embryos 

 I have examined, 8.5 mm. long, the vein runs forward from the pronephros parallel 

 to the aortic root and its continuation, the carotid artery. The vein is separated 

 from the arterial trunk by the ganglia nodosum and faciale. Recalling the earlier 

 position of the vein, it will be seen that it has been transferred from the median to 

 i lie external side of the vagus nerve. In an intermediate stage, I have been able to 

 see the nerve during its transit through the vein, thus confirming an observation of 

 Kastschenko ('87, pp. 275, 276). 



Following the vein farther forward, it is found to pass immediately ventral to 

 the auditory vesicle, directly in front of which it sends a branch around the ganglion 

 faciale to the side of the cranium. Slightly farther forward the vein divides, its 

 branches passing around the more anterior of two ventral processes of the gan- 

 glion faciale. The two trunks thus formed separate. One enters the orbit, and can 

 be traced to the anterior end of the optic bulb. The other passes below the eye, 

 and pursues a nearly straight course to the anterior horn lip. 



A description of the venous system of the adult frog has been given by Gruby 

 ('42) and by Ecker ('64-81). The distribution of the veins which enter the dorsal 

 portion of the pronephros corresponds most closely with the internal jugular of these 

 authors. From the figures of Goette ('75), however, there can be no doubt that 

 the vein I have described corresponds to the one which he calls the external jugular. 

 I have been able to find a vein entering the sinus venosus directly which agrees ac- 

 curately with the inferior jugular of Goette, but I have found none corresponding 

 to the one he calls the internal jugular. It is stated by Goette (pp. 759, 760) that 

 the vein named by him external jugular receives large branches from the maxillary 

 and mandibular regions. This character would seem to connect it with the exter- 

 nal jugular of Gruby and Ecker. According to Goette (p. 765), however, the exter- 

 nal jugular of Gruby and Ecker is the same as his inferior jugular. I believe this 

 statement to be true, and it seems possible that Goette, who confesses that his studies 

 upon the veins did not extend beyond the first larval periods, may have erred in 

 his account of the distribution of these rudimentary vessels. 



Since the preceding description was written, a paper by Marshall and Bles 

 ('90 b ) has appeared, which adds another to the divergent accounts I have re- 

 viewed. The inferior jugular of Marshall and Bles corresponds closely with the 

 vein I have alluded to under that name. The anterior cardinal vein is described by 

 these authors ('90 b , p. 236) as "formed by the union behind the ear of a jugular 

 vein returning blood from the brain and dorsal part of the head, and a facial vein 

 which lies superficially along the side of the head ventral to both eye and ear." 

 These vessels are described in tadpoles, measuring 9 mm. in length. My own 

 observations on larvae of nearly this size do not agree with this description. 



