The oral cirri of Siluroids and the orif^iii of the head in Vertebrates. 403 



Callichthys (Figs. 6 and 7) be of cousiderablc size arc apparently 

 derivatives of the maxillary tentacle. 



As to other Teieo-stei, Balfour remarks of the Salmon : "The 

 anterior bar of the upper arcade is known as the palatine; but it 

 appears to me as yet uncertain how far it is to be regarded as an 

 element primitively belonging to the upper arcade of the mandibular 

 arch which has become secondarily independent in its development; 

 or as an entirely distinct structure which has no counterpart in the 

 Elasmobranch upper jaw. The latter view is adopted by Parker and 

 liuiDcJE and a cartilage attached to the hinder wall of the nasal cap- 

 sule of many Elasmobranchs is identified by them with the palatine 

 rod of Teleostei" (Prepal.). The development of this region in the 

 Salmon has been worked out by Stöhr, who finds that tissue in the 

 anterior trabecular region gives rise to trabeculae, palatine cartilage 

 (Prepalatine), and tissue underlying the maxilla. The fusion of pala- 

 tine and pterygoid elements occurs later. I have followed the process 

 also in Gobius. It might be considered that these ontogenetic stages 

 recapitulate the condition in Siluroids, but that can only be in a 

 very limited sense, inasmuch as the piece in Siluroids is moveable, 

 with special muscles, and does not bear any close resemblance at all 

 to this embryonic condition. Indeed the resemblance is really closer 

 in the adults. 



In the Sturgeon free prepalatine cartilages exist, at any rate in 

 the young animal, outside the basal angle (Basalecke) in front of the 

 mouth. They may be the ethmo-palatines of Parker, but his lack of 

 precision reduces the value of his observations. I cannot tell what 

 Parker meant, since enthusiasm cannot replace accuracy. In Poly- 

 pterus there is a separate ossification (autopalatine, v. Wijhe), in the 

 upper jaw, where it articulates with the ectethmoid, and the cartilage 

 projects forwards beyond this point. This is here called prepalatine. 

 A similar projection occurs in Chlamydoselachus (Garman), so that, 

 in this form, we must conclude that the prepalatine is really included 

 in the jaw, in the region of the articulation with the preorbital pro- 

 cess. In Heptanchus and Hexanchus, a posterior portion of the pre- 

 palatine piece would appear to be represented by the "Lateral process 

 of the ethmoidal region M"", of Gegenbaur, which the latter homologizes 

 with the "Schadelflossenknorpel" of Rays. 



The second tentacle of Myxine is the maxillary tentacle. It lies 

 outside and above the premaxillary and is connected by a bar of 

 softer cartilage to the coronoid tentacle and to the antero-lateral piece 



