DEVELOPMENT OF THE BLOOD VESSELS IN THE FROG. 245 



according to Goette, undergoes changes : the middle portion of its 

 course becomes obliterated ; its ventral end remains as the thyroid 

 artery, from which the lingual artery arises ; while its dorsal end 

 is described as becoming the root of a new artery, the temporo- 

 niaxillary, which runs forwards, outwards, and downwards in the 

 mandibular arch. 



Goette's description is very incomplete. It is, however, sufficient 

 to show that his temporo-maxillary artery is what we have described 

 as the pharyngeal artery, and his account agrees with ours in placing 

 this artery in the mandibular arch. The independent origin of this 

 artery from the aorta, he has apparently overlooked. Concerning 

 the hyoid arch, our accounts agree in describing a vessel in the arch 

 which at first does not open into either aorta or truncus (cf. Fig. 4, 

 E H' and V Y). The connection with the aorta we find later in Rana, 

 but not the connection with the truncus. In the early disappearance 

 of the hyoid vessel along the greater part of its length, the two 

 accounts agree. 



Maurer's* observations were made on Rana esculenta. He finds in 

 tadpoles of 4 mm. length a vessel which he terms the hyomandibular 

 artery, which arises from the truncus arteriosus, runs forwards and 

 outwards across the hyoid arch into the mandibular arch, and then 

 upwards and inwards, to end blindly above the pharynx, the dorsal 

 aorta not being formed as yet. 



In 5 mm. tadpoles Maurer describes the hyomandibular artery as 

 arising not from the truncus arteriosus directly, but from the ventral 

 end of the first branchial efferent vessel. At 6 mm. the relations 

 are much the same, the hyomandibular artery being still connected 

 with the ventral end of the first branchial efferent vessel, and being 

 described as a ventral continuation of the latter, which at a later 

 stage, 9 mm., is said to become the " external carotid " or lingual 

 artery. 



We have found it impossible to reconcile this description with our 

 own observations on tadpoles of Rana temporaria, and can only suppose 

 that the differences in the mode of development of these vessels in 

 allied species are extraordinarily great, or else that Maurer has 

 been misled by the large venous spaces in the floor of the mouth, 



* Maurer, " Die Kiemeu unci ihre Gefasae boi Anuren und Urodelcn Amphibien," 



" Morphologiaches Jahrbuch," xiv., pp. 175-222. 



