528 "• I^- I'OLLARD, 



ilic COL lie of the frontal boue. Kcar the suture of the frontal and 

 I)ostfroutal bones the last branch of the supraorbital system is given 

 oil. It is large and does not correspond to an ordinary branch but 

 is rather a continuation of the main canal. Near its origin it contains 

 a sense organ. It lies in a groove of the frontal and squamosal, and 

 leads to the last pore, the fifth or perhaps morphologically the sixth, 

 of the supraorbital system. The main canal in the postfrontal near 

 the edge of the latter unites with the infraorbital system and it is 

 noteworthy that it is directed downwards and outwards in its last 

 portion. 



Continuation of the main line. Behind the junction of 

 the supra- and infraorbital systems in the postfrontal the main line 

 continues backwards near the internal edge of that bone and passes 

 into the squamosal within which it shows a sense organ, No. 6 and 

 then in the anterior third of the squamosal it gives otï the operculo- 

 mandibular system at an angle of 60^. It then makes a sharp curve 

 and at the apex of the curve is situated the 7 th sense organ. This 

 lies on the inner wall of the canal and just opposite to it a long branch 

 is given otf which runs directly outwards in the squamosal and is 

 nearly of the same calibre as the main stem. Reaching the edge of 

 the bone it turns backward at a right angle and then lies for some 

 distance in a groove of the bone termed by Huxley suprascapula. 

 It opens by a pore near the suture. 



The main canal passes backwards and outwards in the squamosal 

 near the edge of which it encloses the 8th last cranial sense organ. 

 It then continues into the suprascapula and on as the lateral line of 

 the body. 



Innervation. For convenience it is best to regard the lateral 

 line system in the adult Clarias as one organ sui generis, — as much 

 so as the auditory organ for example and to think of the nerves 

 merely as branches corresponding to the various branches of the audi- 

 tory nerve. They all arise from the same region of the brain though 

 they take different directions. 



The first five organs of the supraorbital line are supplied as 

 shown in the figure by the Ramus ophthalmicus superficialis. The 

 twig which supplies the first sense organ does so from the median 

 side having curved beneath the canal. The remaining four organs 

 are supplied each by a separate twig and in the case of organs four 

 and five the twig runs backward. 



The five organs of the infraorbital line are supplied from the 



