THE GENIO-HYOIDEUS MUSCLE. 159 



adult life and then in so exceedingly variable a manner 

 as to sug-gest that the muscle is in a process of degener- 

 escence (Allis, '97, p. 700). In this fish the genio-hyoi- 

 deus and the intermandibularis muscles are clearly sup- 

 plied from the V, and the trigeminal nerves which supply 

 them {r. ghs. and r. ghi.) are evidently comparable with 

 my anastomosing branch V-VII. 2. Like the latter they 

 contain general cutaneous fibres and Allis thinks ('97, p. 

 638) also communis fibres for the te:.minal buds found on 

 the gular plate and the lower end of the gill cover in 

 Amia. In Lota, too, (Goronowitsch, '96, p, 40) the inter- 

 mandibularis is clearly innervated from the trigeminus 

 (his Trig. I). 



In forms like Esox, in which the so-called genio-glossus 

 is innervated from both the VII and V nerves (Vetter 

 '78), we may assume that the muscle represents both 

 facial and trigeminal constrictor systems, comparable 

 with those of Ceratodus, while in Menidia and most other 

 teleosts the VII portion has been lost and the m. " genio- 

 hyoideus," together with the intermandibularis, represents 

 the ventral constrictor muscles of the trigeminus segment, 

 the facialis constrictor muscles being represented only by 

 certain dorsal opercular muscles and by the branchio- 

 stegal muscles. 



Ruge ('97) is not willing to accept this interpretation; 

 but, being convinced that these muscles must in all forms 

 belong to the facial segment, he makes the entirely 

 gratuitous assumption that the motor fibres for these two 

 muscles, which in Ceratodus and teleosts appear to come 

 from the trigeminus, really come as anastomosing fibres 

 from the facial. 



This assumption he makes also for the innervation of 

 the intermandibular muscle of Amphibia, Reptilia and 



