THE GENIO-HYOIDEUS MUSCLE. 157 



shown in Acanthias that a neuromere is found in this 

 position in the brain, but it is early lost, leaving no trace 

 behind. We cannot, then, reasonably look for such a seg- 

 ment in the adult of the more highly specialized teleost. 



iv. — The genio-Jiyoideus and inter mandibularis muscles. — 

 Previous investigators have been unable to determine the 

 innervation of these muscles with certainty, as the 

 methods of dissection are obviously inadequate to unravel 

 the anastomoses between the VII and V nerves. 



Stannius mentions (p. 23) that the m. genio-hyoideus in 

 some cases contracts when the motor V (his first root) is 

 stimulated; nevertheless he is inclined to regard the 

 proper innervation of the muscle from the facialis. He 

 also found (p. 62) that in Esox stimulation of the truncus 

 hyomandibularis causes movements of the branchiostegal 

 membrane and also weak movements of the lower jaw, 

 and this would favor that view. 



Vetter ('78, p. 515) found that in this species the m. 

 genio-hyoideus is supplied largely by extensions of the r. 

 hyoideus which run forward into it after supplying the 

 branchiostegal muscles (m. hyo-hyoideus). This is not 

 mentioned by Stannius and certainly is not true in Men- 

 idia, yet I may account for the movements of the jaw 

 observed by Stannius upon stimulation of the truncus 

 hyomandibularis. 



Subsequent studies (July, iSgg) have shown me that this is, how- 

 ever, true in Gadus. Or at any rate the r. hyoideus runs forward 

 from the branchiostegal membrane in this species to anastomose with 

 the nerve for the genio-hyoideus within the substance of that muscle. 

 The figure and description by AUis ('97, p. 613 and Fig. 43) indicate 

 a similar condition for Amia. 



Pending an exact embryological examination, the mor- 

 phology of the pre-hyal ventral musculature of the teleosts 

 has remained obscure. It is supplied, at least in part, by 



