353 



The fourth tentacle is small but has a well developed rootpiece. 

 It is supplied by a branch from a deeper nerve of the Trigeminus. 

 To its parts the name mental may be applied. 



Next in order follows the „Zungenbein" which is composed of 

 several pieces. The anterior lateral paired piece (W. of Müller) 

 which is connected with the coronoid piece is the rootpiece of a ten- 

 tacle, the submandibular, the tentacle itself having been lost in Myxine. 



There is conclusive collateral evidence of its former existence (as 

 will be shewn later) apart from the fact that a nerve from the most 

 ventral portion of the Trigeminus stands in the precisely normal topo- 

 graphical relation. The piece is the Meckelian or mandibular piece, 

 the nerve may be termed the submandibular nerve and, it may be 

 added, the muscles which are attached to the piece must be regarded 

 in part as the homologues of the jaw muscles of the higher vertebrates. 

 The remaining pieces of the „Zungenbein" are a median pieces 

 (W) and a paired posterior piece (X). The median piece is in con- 

 tinuity with the posterior piece by a slight bridge of softer cartilage. 

 There appears no reason to doubt that these represent the rootpieces 

 of two more tentacles which have disappeared. 



Finally the nasal tube is surrounded by rings of cartilage of the 

 peculiar histological structure and these are worked by muscles of the 

 same type as those of the tentacles. The sensory and motor supply is 

 from the Ophthalmicus. Therefore there is reason to believe that these 

 structures also belong to the tentacular system and the result is arrived 

 at that originally the ancestors of Myxine must have pos- 

 sessed at least 8 pairs of oral cirri. The branches of 

 the ophthalmicus, the maxillaris, coronoideus, men- 

 talis and submandibularis are nerves corresponding 

 to several segmentally arranged nerves of Amphioxus. 



Furthermore since the rootpiece of the maxillary tentacle is con- 

 tinuous with the skull it is possible to regard the cranium as an 

 expansion of this rootpiece which in Myxine comes to protect the 

 auditory organ and in higher vertebrates the brain and olfactory 

 organ as well. 



Gnathostomous Vertebrates. 



Among the remaining animals which possess tentacles the Siluroids 

 take a prominent place and I have had the good fortune to be able 

 to examine a fair number. Some which I investigated at Freiburg i. B. 

 apparently dated from the expedition of Bilharz to Abyssinia, others 

 Prof. Wiedersheim procured for me through the kindness of Prof. 



