354 



Möbius in Berlin and Dr. Günther of the British Museum. Prof. 

 Dohrn with great generosity allowed me at Naples to take the 

 drawings for a wax model from his sections of a young Silurus glanis. 

 My other acknowledgments, so far as this work is concerned, are to 

 Prof. Weldon at London for specimens of Myxine and to the deceased 

 Prof. Milnes Marshall for a specimen of Protopterus and some Dacty- 

 lethra larvae. 



By means of projections from sections and wax models I have 

 examined among Siluroids, Clarias, Auchenaspis, Silurus, Callichthys 

 Trichomycterus and Chaetostomus — for the most part those animals 

 whose lateral line system I have described elsewhere *). 



The typical number of tentacles possessed by Siluroids in 5 pairs 

 but no one form has all fully developed. The most anterior pair, 

 occurring in Clarias and Trichomycterus is situated by the nose and 

 may be termed the nasal. It is supplied by the ophthalmicus pro- 

 fundus. 



It may be considered as the homologue of a hypothetical nasal 

 tentacle in Myxine. There is a nasal „labial" in Elasmobranchs such 

 as Scyllium, where the labial occurs in a similar relation to the external 

 opening of the nose. The trelliswork of the nose of Myxine is to be 

 regarded as a derivative of this tentacle and possibly also the trellis- 

 work of the nose of Protopterus. 



In Siluroids a block of precartilage at the end of the snout re- 

 presents the rootpiece of the premaxillary tentacles, i. e. the „vordere 

 knöcherne Stütze der Schnauze" of Myxinoids. In some Teleostei this 

 becomes true hyaline cartilage e. g. in Labrus, Cottus, Gobius, Balistes 

 et cetera and in them it supports the premaxillary bone which is to 

 be regarded as a bone formed from dermal teeth external to this 

 skeletal piece. The piece is the intermaxillary cartilage of Owen. 

 There are no muscles in connection with it and correspondingly the 

 ophthalmicus profundus is purely sensory. 



The second tentacle, the maxillary is present throughout the 

 Siluroids and is supported by a large block of hyaline cartilage which 

 may be termed the prepalatine or, when perichondrial bone arises 

 round it, the autopalatine (van Wijhe 2 ). This piece is well known 

 (Stöhr, Parker) to arise in Teleostei independently of the rest of 

 the cartilaginous upper jaw and in fact in Siluroids it only separates 



1) Zoologische Jahrbücher, Abt. f. Anatomie, 1892. 



2) van "Wijhe, Ueb. d. Visceralskelett u. d. Nerven d. Kopfes d. 

 Ganoiden u. von Ceratodus, Niederl. Arch. f. Zoologie, Bd. V, 1882, 



