ORAL CIRRI OF SILUROIDS AND ORIGIN OF THE HEAD IN VERTEBRATES. 27 



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 of the 

 tongue apparatus, the piece W of Midler and my Mck (Fig. 11). To 

 the base of this tentacle, but not fusiug with it, extends the process 

 from the cranium, which Miiller termed the cartilaginous process at 

 the anterior end of the palatal ridges," the Processus spinosus of 

 Fiirbringer, or the Prepalatine of Parker. 



The coronoid tentacle extends downwards and has an expanded root 

 piece of hard cartilage. The prepalatine piece is in continuity with 

 the ethmoid region, and thence with the subocular bar (Gaumenleiste 

 of Miiller), and the subocular bar is continuous with the auditory 

 capsule and basilar part of the skull. 



Miiller makes the following remarks on the origin of the first 

 cranium. On the fibrous membrane of the chorda tube arise paired 

 cartilagiuous rudiments of basilar pieces, running out into the auditory 

 capsules and forwards as lateral wings. This is shown in Ammocoetes 

 and Myxine. From this stage chondrification has proceeded further, 

 and by various steps the coudition of the chondro-cranium of higher 

 vertebrates is attained. This is the simple view of Miiller, and to me 

 it seems still the most correct. Indeed where the conception of 

 recapitulation in ontogeny has, in spite of the arguments of v. Baer, 

 Gegenbaur and others, been introduced, there has often been great 

 retrogression from the truth. Miiller does not come to any conclusion 

 as to the origin of the subocular regions and of the prepalatine piece. 

 The prepalatine piece I regard as the root piece of a tentacle, and since 

 there is no break of continuity in the skull of Myxinoids we may perhaps 

 regard the subocular bar and £1 quadrate " regions as outgrowths and 

 extensions of fused vertebral and tentacular elements. 



This would mean that the autostylic condition of suspension of the 

 jaws is the most primitive condition. To this conclusion I have come 

 iu a recent paper from quite different grounds. 



The Labials (sensu strictiori). 

 Comparison of the traces of premaxillary, maxillary, and coronoid 

 tentacles brings us to the question of the labials, as the term is strictly 

 used by Gegenbaur. I shall treat of the subject rather in a historic 

 way. 



