108 EDWARD PHELPS ALLIS, J UN. 



Hyoiuandibular Caual, 



Tlie hyomandibular caual, usiuo- the name adopted by 

 Ewart (18) iu his descriptions of Li^margus, begins at the 

 point where the infra-orbital canal bends laterally and 

 forward, just before it passes from the ventral to the lateral 

 surface of the head. It is there in direct communicatiou 

 with the infra-orbital caual between organs 54 and 55, that 

 is, between the second and third groups of the organs of the 

 line. From there the canal runs almost directly backward, 

 lying close to and parallel to the lateral edge of the ventral 

 surface of the head. Posteriorly it gradually approaches 

 that edge, and at a certain distance beyond the transverse 

 plane of the spiracle reaches it, and there turns upward and 

 backward around it, and appears on the lateral surface of the 

 head. Continuing in this upward and backward direction a 

 relatively short distance, it reaches a. point something more 

 than half the distance backward from the spiracle to the 

 first gill-slit, and there ends. 



The exact number of organs in the canal could not be 

 determined, the organs and related nerves in the posterior 

 part of the canal being so slightly developed that they could 

 not be recognised with certainty. The primary tubes, most 

 of which had undergone subdivision, would seem to indicate 

 that there were about forty organs in the canal. The organs 

 are quite unquestionably all innervated by branches of a hyo- 

 mandibular part or division of the maudibularis externus 

 facialis, but this could be definitely established for the first 

 twenty-four organs only, counting backward from the anas- 

 tomosis with the infra-orbital canal. The remaininof oro-ans 

 and their innervating nerves could not be traced. 



Mandibular Canal. 



The mandibular canal is relatively short, lies parallel to 

 the hind edge of the mouth, and extends from near the 

 middle line of the head backward and laterally to the level 

 of the outer edge of the upper labial fold. It lies, in the 



