OSTEICHTHYES 



on to the head. By a subdivision and branching of the pore canal 

 a number of small pores may replace the original primary pore. 



AVe have already seen (p. 125) that the canals of the lateral- 

 line system follow a fairly uniform course on the head in the 

 various "-roups of fish. The Elasmobranchii and Osteichthyes agree 

 well in this respect (Allis [9, 19], Garman [148], Clapp [78], Herrick 

 [210], Collinge [85-89], etc.). Now the connection established 

 with the cranial bones is as follows (Figs. 1 96, 500, A). The trunk 

 lateral line passes by means of the post-temporal on to the supra- 

 temporal or the pterotic (squamosal) ; from this point a transverse 



sc e A 



"9 



Frr,. 193. 



Laueiscus cephalus, L. A, Longitudinal section through the skin, scales, ami muscles. li, 

 surface view of body-wall : the skin has been removed un the left, and the myotonies exposed 

 lie low on the right, c.t, connective tissue ; i p, epidermis ; /.«•, lateral- line scale ; ( ». myotome : 

 ", opening of lateral-line canal ; sc, scale in connective-tissue pocket : si; skin. 



branch is often sent off towards the middle line running as a rule in 

 the supratemporal bones — it may be called the supratemporal or 

 occipital branch. The organs in this region of the canal are supplied 

 by the supratemporal twig of the vagus. The main line then con- 

 tinues horizontally through the pterotic, forming a short temporal 

 canal supplied by the otic branch of the glossopharyngeal (this 

 short region does not always occur). The canal is prolonged 

 forward to behind the orbit — postorbital line — through the pterotic 

 and post-frontal. It is supplied by the otic branch of the facialis. 

 Next it passes below the orbit and forwards to the nostrils ; the 

 ramus buccalis facialis supplies this infraorbital canal, which passes 

 through the post-, infra-, and preorbital ('lachrymal') bones. 

 Starting from the junction between the postorbital and infra- 



