119 



presumptiou to be made is, that part of this uerve had been removed 

 by dissection, and, Fritsch, recognizing the remainder as an unde- 

 scribed nerve designated it as "supernumerary". Although his carefully 

 made figures embrace brains of several other forms described in this 

 paper, the presence of the new nerve is not indicated in any of them. 



Since the publication of Fritsch's Memoir, the selachian brain 

 has been subjected to searching analysis by gross dissections and 

 microscopic sections, but, neither in the papers of Balfour and 

 Marshall, nor in the large number of more recent investigations, is 

 there any mention of this nerve in Selachians prior to my paper 

 referred to above i). 



While this statement will hold true for Selachians, it will not 

 stand for all other groups, provided the nerves described, respectively, 

 by PiNKUS and Allis be homologous with the one described in 

 this paper. 



PiNKus, in 1894, published in the Anatomischer Anzeiger under 

 the title "Über einen noch nicht beschriebenen Hirnnerven des Proto- 

 pterus annectens", a preliminary account of a new nerve in that fish. 

 Soon after , there appeared in his complete paper ('95,) a further 

 description and a reconstruction showing the position of this nerve 

 on the ventral surface of the brain. 



PiNKUs describes the nerve in the adult Protopterus, but gives 

 no facts as to its embryonic history. He observed no ganglion 

 connected with it. His summary relating to this nerve in his complete 

 paper ('95, p. 332) is as follows: "Ein bisher nur bei Protopterus 

 nachgewiesener, markloser Nerv, welcher am Vorderende des Recessus 

 praeopticus das Zwischenhirn verläßt, lagert sich dem Olfactorius an 

 und verläuft neben ihm bis an das Vorderende der Nase, wo er 

 in einen Zellhaufen am Dach der vorderen Nasenöfi'nung sich verliert. 

 Eine kolbige Anschwellung dieses Nerven, welche durch die Einlagerung 

 großkerniger, von allen anderen nervösen Zellen des Protopterus an- 

 scheinend verschiedenen Zellen bedingt ist, macht es wahrscheinlich, 

 daß wir es hier mit einem neuen Organ zu tun haben." 



Although the author does not recognize any part of the nerve as 

 a ganglion, I venture to suggest that it is possible that the "kolbige 

 Anschwellung" of the nerve may be ganglionic. 



1) The only mention of it in Selachians which I have seen outside 

 my paper is a very recent one. v. Kupffer mentions it, incidentally, 

 as being near the Recessus neuroporicus, and indicates that further 

 treatment of it will be made in another place. See Handbuch der ver- 

 gleich, und experiment. Entwickelungslehre, Liefer. 14 und 15, 1903, 

 p. 84. 



