406 H- B. POLLARD, 



substratum, but on such, tlie bone persisting while the cartilaginous 

 substratum retrogrades and finally disappears. He then set forth his 

 view that the labial arches are to be compared with arches of the 

 inner visceral skeleton or branchial bars. This has been the basis 

 for most of the modern Gennan views. 



Huxley (1876) compared the lower labials of the frog to the 

 annular cartilage of the lamprey and the "incomplete ring" of Am- 

 phioxus, while the upper labials of the frog are the anterior dorsal 

 cartilages of the lamprey, 



Balpoue (1882) says of the labials : "The meaning of these car- 

 tilages is very obscure; but from their being in part employed to 

 support the lips and horny teeth of the Cyclostomata and the Tad- 

 pole I should be inclined to regard them as remnants of a primitive 

 skeleton supporting the suctorial mouth with which, on the grounds 

 already stated I believe the ancestors of the present vertebrates to 

 have been provided." 



Howes (1891) has compared the labials of Chiinaera and Marsipo- 

 branchs. His figures of Myxinoids are partly erroneous as to facts, 

 being apparently compounded from museum preparations. 



The question of the homology of the labials in Chimaera seems 

 to me to be decided by the work of Vettek, the value of which can 

 hardly be overestimated. He describes in detail the musculature of 

 the labials in Chimaera. 



These structures are worked by four muscles ; the Musculi labiales 

 anterior and posterior, and two portions of the Levator anguli oris. 



The Labialis anterior is supplied by an anterior motor branch 

 of the Trigeminus and corresponds closely to a portion of the Copulo- 

 tcntaculo-coronarius muscle of Myxine (FCriuunger) the "Kopf JJ' 

 des zweiköpfigen Herabziehers des Mundes" (Müller) which, as I have 

 shown, is innervated by a branch from the premaxillary nerve. 



The Labialis posterior is a portion of the Kopf U of Müller, and is 

 supplied by a most posterior branch of tlie motor part of the Trigeminus, 



The portions of the Levator anguli oris are the Retractores 

 tentaculorum of Myxine. 



We have therefore in these labials remnants of premaxillary, 

 maxillary and coronoid tentacles. To put the homologies, which I 

 maintain, into unniistakcablc form, I will refer to Müller's figure of 

 Callorhynchus. I take his "äusserer Nasentiiigelknorpel e" to be the 

 remnant of the premaxillary tentacle, his "oberer Seitenknorpel 

 des Mundes c" to be a remnant of the maxillary tentacle, his "unterer 



