The oral cirri of Siluroids niid the origin of the head in Vertebrates. 405 



lartilage in the nasal lobe, and the niaxillaries by the "Schädelflossen- 

 knorpel". 



On the maxilhi of Teleostei he remarks: "Since the labial bone is 

 unprovided with teeth in almost all the fish, it has little resemblance 

 to the ordinary maxilla ; but in order to be convinced as to its nature, 

 it is enough to observe it in the trout or salmon, and thence to follow 

 it in its various forms" (I may here remark that the Teleostean 

 maxilla only partly corresponds to the maxilla of other vertebrates 

 e. g. Polypierus, where it is mainly a "suborbital" bone). 



On the Siluroids he remarks: "The intermaxillary, without a 

 pedicle (ascending process), is situated under the anterior, more or 

 less broadened edge of the skull and at each of its extremities is a 

 small maxilla, which, becoming flexible, is prolonged into a long fila- 

 ment or barbel ; in a word, the principal barbel of Siluroids is their 

 maxilla prolonged". As to CJiimaera: "In the thickness of the lip are 

 found three bones (cartilages), which one recognises as the inter- 

 maxillary, maxillary and the palatine arcade; this last is entirely 

 suspended by muscles and ligaments, without articulating with anything". 



Subsequent investigation has confirmed the remarks of Cuvier to 

 a wonderful extent. 



R.vTHKE (1823) compared the labials of Petromyzon to the 

 'ivnorpelriemen" of Amphioxus (I quote from memory of the text). 



Johannes Müller (1835) criticised Cuvier's accounts and views, 

 and attempted to show that the labials are structures not belonging 

 to the general plan of the vertebrates, and that the upper jaw of 

 sharks corresponds to the upper jaw of other vertebrates. "The tooth- 

 bearing cartilage of Plagiostomi can be nothing else than the upper 

 jaw (maxilla), while the labial bones are, as we have already shown, 

 accessory pieces. Probably in the tooth-bearing cartilage, maxilla and 

 premaxilla are united". The palatine arch of e. g. Teleostei is, ac- 

 cording to Müller, represented by accessory cartilages in Narcine 

 and other fish. Müller makes many valuable comparative obser- 

 vations, and gives a complete account and figure of Cnllorhynchus. 

 His views have not met with acceptance, and have been abandoned 

 since Hertwkj's researches on dermal bones. 



Gegenbaur (1872) gave a complete account of the structures in 

 Selachii, accepting Cuvihr's homology of the preraaxillary and maxil- 

 lary labials, drawing attention however to the distinction between the 

 dermal bone and its subjacent tissue. The premaxillary bone must 

 be imagined as developed phylogenetically , not from a cartilaginous 



