174 John beard. 



gill muscles. According to Van Wijhe, the dorsal branch becomes 

 intimately connected with the skin, and is there in connection with 

 the rudiments of the so-called sense organs of the lateral line. He 

 further holds that the sensory epithelium takes part in the formation 

 of the nerve. In this respect the dorsal branch differs from the ventral 

 one, which does not, according to any writer, arise either wholly or 

 partially from the skin, but is a direct outgrowth of the neural crest 

 (Marshall). The branch in front of the cleft is developed later than the 

 other branches, but how is still uncertain. At any rate, both Professor 

 Froriep and I have failed to gather from Van Wijhe, who alone has 

 studied the development of this branch, how this branch and the 

 Ramus pharyngeus are developed. In Amphibians, Gotte 1 long ago 

 held that the so-called dorsal branches were split off from the skin. 



These various branches have all received general names, some of 

 which require alteration in view of the researches contained in this 

 paper. The branch posterior to the cleft is called the main or posterior 

 branch (Balfour), and post-trematic by Van Wijhe ; in this paper it 

 will be spoken of as the post-branchial nerve. The branch in front of 

 the cleft, viz. the prse-trematic of Van Wijhe, I shall call the prse- 

 branchial nerve. 



The Ramus pharyngeus of Van Wijhe will retain the same name 

 when spoken of here. But now for the so-called dorsal branches ; of 

 all the general names this is by far the worst. It is true that the name 

 has been employed by many distinguished zoologists, Stannius, Gegen- 

 baur, Balfour, Marshall, and Van Wijhe, and that therefore to propose 

 a change, except for very weighty reasons, would be a very high- 

 handed and arbitrary proceeding. However, it must be done, and on 

 grounds to be afterwards stated. 



Though some of these various so-called dorsal nerves may come to 

 occupy a dorsal position, still, as was first mentioned to me by Pro- 

 fessor Dohrn, it is morphologically wrong to regard them as dorsal. 

 Of the truth of this I have fully convinced myself, and hope soon to 

 convince the reader also. I have, however, no means of knowing 

 whether my reasons for rejecting the name are the same as Professor 

 Dohrn's. These branches will be described by the general name of 

 supra-branchia I. 



So much for a general view of the adult condition. A schema of 

 the development in Elasmobranchii would be as follows. (This 



1 A. Gotte, ' Entwiekelungsgesch. d. Unke,'1875. 



