170 
As, however, in the single series of sections on which fig: 
23 was based it was innervated by the inner buecal of the 
right side, it either cannot represent the anterior end of 
the left supraorbital, or such an innervation must be 
anomalous. In the meantime, however, we shall follow 
Traquair, and regard it as belonging to the supraorbital 
system. Another very small follicle was found behind it, 
but it was very aborted and contained no sense organ. 
The innervation of the former structure suggests that it is 
a modified pit organ, especially as such occur typically in 
Teleosts at this region. 
The Supraorbital commissure (s. 0. c.).—Arises from 
the canal on the ocular side, as above described. A sense 
organ is situated just at its origin, which projects partly 
into the supraorbital canal itself. The commissure passes 
upwards and forwards almost at right-angles in the sub- 
stance of the right frontal. It then bends sharply inwards 
at right angles (indicated by a circle in fig. 25), and at 
once enters the left frontal. Just at the turn an unpaired 
surface tubule (3) is given off, and this undoubtedly cor- 
responds to the fourth unpaired median tubule of the Cod. 
Its position in the Plaice is only apparently anomalous. 
The commissure passes almost transversely but slightly 
forwards across the body in the left frontal. Arrived at 
the other side it bends gradually downwards but still for- 
wards (a large sense organ being situated at the turn), and. 
thus passes into the left supraorbital. The sense organ in 
the commissure on the left side is situated much higher 
up than on the other side, and is thus entirely within the 
commissure. It is innervated by the R. ophthalmicus 
superficialis vii. of the left side. The commissure also is 
passing forwards from right to left during the whole of its 
course. 
To sum up the supraorbital system, the right supra- 
