— 75 — 



System arises where the canals of opposite sides anastomose in the mid-dorsal line. The canal con- 

 tains two sense organs, one lying in the lateral extrascapular and the other in the parieto-extra- 

 scapular; both organs being innervated by branches of the supratemporal branch of the nervus lineae 

 lateralis vagi. 



The supraorbital canal begins at the anterior end of the nasal, traverses that bone, and then 

 runs backward in the frontal nearly to its bind edge. The anterior dendritic System of the line lies 

 at the anterior end of the nasal and is represented by a small and somewhat scattered group of pores. 

 The 2nd. system of the line arises from the canal as it passes from the nasal into the frontal. It is 

 larger than the first system and sends a long branch laterally and downward in the dermal bridge 

 between the two nasal apertures. This branch opens on the outer surface by several pores, and in 

 one specimen, as alrcady stated, one of these pores seemed to have anastomosed with a pore or pores 

 of the anterior dendritic system of the main infraorbital line, thus here establishing a connection 

 between these two lines. The 3rd., 4th. and 6th. Systems all arise from that part of the canal that 

 lies in the frontal, the canal then ending while still in that bone, in the 7 th. or terminal system of 

 the line. The 5th. system, which should normally be formed between the 4th. and 5th. organs 

 of the line, is wholly wanting even in the young specimens examined in sections. The trunk of the 

 3rd. System is directed forward, and branching gives rise to an elongated group of from twelve to 

 eighteen pores. The trunk of the4th. system is directed postero-mesially and traverses the frontal to its 

 mesial edge, where it anastomoses with its fellow of the opposite side to form the frontal (supraorbital) 

 cross-commissure. The single median pore here first formed by the fusion of the single primary 

 pores of opposite sides has, by subsequent division, given rise to a small median group of pores. 

 The trunk of the 6th. system runs postero-laterally in the frontal, to its lateral edge, where it 

 anastomosed with the 9th. trunk of the main infraorbital to form a double system. Having given 

 off this trunk, the canal turns posteriorly and issues from the frontal beneath the frontal spine, 

 the 7th. or terminal system of the line being represented by a circular group of some ten to 

 fifteen pores. 



The supraorbital canal contains six sense organs, this being one more than is warranted by 

 the number of dendritic Systems actually found in the fish. One of these organs lies in the nasal, and 

 five in the frontal. The organ in the nasal is normal in its relations to the trunks of the dendritic 

 Systems, as are also the first two organs in the frontal; one of these latter organs lying between the 

 trunks of the 2 nd. and 3 rd. Systems of the line and the other between the trunks of the 3 rd. and 

 4th. Systems. The fourth organ lies partly opposite and partly posterior to the trunk of the 4th. 

 System, the fifth organ being similarly related to the trunk of the 7th. or terminal system. The 

 sixth organ is a small one lying in the trunk of the 7 th. or terminal system of the line. Between the 

 fourth and fifth organs there is no primary tube in Scorpaena, but both in Cottus scorpius and 

 Cottus octodecimospinosus there is here a small tube. As, otherwise, the organs and tubes are exactly 

 similar in the three fishes, a tube has certainly either aborted or never been developed, in 

 Scorpaena, between the fourth and fifth organs of the line. These two organs lie quite close together 

 and are innervated by branches of a single branch of the ophthalraicus lateralis, the other organs 

 of the line all being innervated by independent branches of the same nerve. The nerve that inner- 

 vates organs 4 and 5 perforates the frontal, at the base of its ventral flange, to reach the organs it 

 supplies, sometimes separating into its two parts external to the frontal and sometimes while tra- 

 versing that bone. In one young specimen examined in serial sections the branch to organ 5 separated 



