112 BULLETIN OF THE 



In connection with the embryogeny, segmental distribution of the 

 nerve-endings, etc., it is found necessary to refer to a number of publi- 

 cations relating mainly to other organs of the Selachia, or to similar 

 organs in other classes of animals. Semper, Goette, Eisig, Dercum, Van 

 Wijhe, Hoffmann, Wright, and others, have all put forward contribu- 

 tions which may not be overlooked, though not in most cases directly 

 connected with the subject of this paper. 



Solger, 1878-80, is the author of a number of papers relating to the 

 microscopical anatomy in Selachia, Holocephala, and Fishes. 



Sappey, 1880, in his " Etudes sur I'appareil mucipare et sur le sys- 

 teme lymphatique des Poissons," did some work on the Selachia, the re- 

 sults of which are indicated on several plates illustrating the courses and 

 connections of the canals, as well as of the mucous ducts, of a Skate, 

 probalily Raia clavata, and of a Shark, probaVjly Galeus. This is the 

 nearest approach to a delineation of the canal system since the attempt 

 of Monro, nearly a centui'y previous. Some peculiarities are to be seen 

 on the plates in Sappey's publication, which apparently make the species 

 dissected for the drawings to differ greatly from others of their genera. 

 A number of the items of greatest variance are evidently the conse- 

 quences of incomplete observations. The most questionable points on his 

 Skate are these : (1) the connection of prenasal and subrostral ; (2) the 

 absence of connection between subrostral and rostral ; (3) absence of 

 junction of suborbital and orbital ; (4) the disunited condition of upper 

 and lower sections of the pleurals ; (5) the ending of the upper pleural 

 near the orbit ; (G) the presence of a transverse canal between the cra- 

 nials in front of the orbital ; and (7) the absence of the aural. On his 

 Shark neither aural, orbitals, nor orals would appear to have been 

 discovered. 



De Sede, 1884, in his " Recherches sur la ligne laterale des Poissons 

 osseux," details the results of a number of essays toward a determination 

 of the uses of the organ. In this work he also instituted a number of 

 comparisons for the purpose of ascertaining its value in classification. 

 He occupies the position of a pioneer in the directions of his study. 

 From his experiments he decides that the line is a tactile organ of ex- 

 treme delicacy. In the Selachia the canals demand higher rank as aids 

 in classification than he accords them in the Teleostei, and his conclu- 

 sion that the apparatus is more necessary to the least migratory fishes 

 is dii'ectly opposed to what is seen on such Sharks as Alopias, or such 

 Rays as Dicerobatus. 



P.card. 188.0. has made one of the most recent and important contri- 



