Nos. IAXD2.] ANATOMY OF SCOMBER SCOMBER. 177 



seemed to be the conditions in the apparently exceptional speci- 

 mens of Scomber. 



There are thus, in Scouiher, eight dendritic systems and seven 

 sense organs in the supraorbital canal. Two of the dendritic sys- 

 tems are terminal systems, and a third one fuses with an infra- 

 orbital system to form a double system. Three of the sense 

 organs of the line lie in the nasal, and four in the frontal, in the 

 positions shown in Fig. la. All of these organs, excepting one, 

 are innervated by branches that arise either directly from the 

 ophthalmicus superficialis facialis, or from that nerve fused with 

 the ophthalmicus superficialis trigemini. The one organ that is 

 not so innervated is the anterior organ of the line, which organ is 

 innervated by a nerve that is undoubtedly a branch of the buccalis 

 facialis. The canal in Scomber thus differs radically in this re- 

 spect from the canal in Amia, and the only explanation possible is, 

 as already stated, that the anterior end of the nasal bone of Scom- 

 ber is the homologue of either one half of the ethmoid bone of 

 Amia, or of the antorbital bone of that fish. In Amia, the short 

 bony tubes that form in connection with the first two organs of the 

 main infraorbital line have fused with each other, and with the 

 corresponding bones on the opposite side of the head, to form the 

 so-called median, dermal ethmoid. In Scomber the tube formed 

 in connection with the first organ of the same line has fused with 

 the anterior end of the true nasal bone. This seems to throw an un- 

 expected light on many questions relating to the dermal bones of 

 the skull of fishes, and it becomes more than ever evident that 

 the development of those parts of the lateral system that are 

 related to the bones of the skull must be definitely known before 

 their homologies can be properly determined. 



In Chimcera, Cole (No. 15) finds two organs of the supraor- 

 bital canal innervated by a branch that has its apparent origin from 

 the ophthalmicus profundus trigemini. The short section of canal 

 containing the organs so innervated is said to lie between two 

 long and nearly equal parts of the canal, the organs of both of 

 those parts being innervated by branches of the ophthalmicus 

 superficialis facialis. The origins, from the main nerves, of the 

 branches that innervate the organs of these two long sections, and 

 the subsequent subdivision of most of them, indicate sufiiciently, 



