152 ME. r. J. COLE ON THE STBITCTURE AND MOEPHOLOGT OF 



to the segmental sensory papillre of Annelids. On p. 577 et scq. he confirms for Squalns 

 the observations of Wilson on Set^raims and Mitrophanow on Acanthias and otlier 

 Elasmobranclis as to the common anlage of the lateral sense organs and auditory 

 oro-an, and states : — " MitroiAanow departs from the nsual point of view that the organs 

 of the lateral line are metaraeric, and in that particular, I think, I should be inclined 

 to follow him." Strong (1895, 204) is more emphatic on the point. He says (p. 197) : 

 " It is also evident that the lateral line system has no specially segmental character, 

 and that it cannot properly be used in the manner in which it has been attempted to 

 use it, as a general guide in determining the segmentation of the head." 



Miss Julia Piatt (1896, 158) argues from the opposite point of view*. She states 

 (pp. 502-503) : — " Since Mitrophanow claims as the result of his study that the segmenla- 

 tion of the lateral-line system is entirely secondary, I shall be interested to discovei; when 

 I again have my Acanthias material with me whether traces of primitive segmentation so 

 evident in Necturus cannot also there be found, for it is dilficult to believe that the 

 great similarity which exists in the position and direction of the main lines of sense 

 organs in Necturus and Acai/thlas should not be the result of a similar coiirse of 

 development." Miss Piatt also describes four of the sense organs of the infra-orbital 

 line as being partly innervated by the ophthalmicus profundus, and concludes (pj). 530- 

 531) : — " I do not, for this reason, include the trigeminus among the lateral line nerves, 

 bvit should nevertheless hesitate to say that the ' trigeminus proper does not participate 

 in the innervation of the lateral line system.' " With regard to the ultimate fate of 

 Beard's branchial sense organs, Minot (1897, 140) says (pp.706 & 709) : — "We have 

 further to emphasize those traces which have been discovered of long series of sense 

 organs, of Avhich the nose, eye, and ear are probably derivatives, in the ancestors 

 of the vertebrates, although in all known vertebrates most of these series have become 

 rudimentary or lost. The serial sense organs I designate under the comprehensive name 

 of ganglionic sense organs. There are probably two, and only two, series along each 

 side of tlie body : one series, the ujiper, corresponds to the lateral line of comparative 

 anatomy, the other to the epibranchial line." After pointing out the diiferences between 

 the two series, he concludes : — " The sense organ above the gill cleft [i. e. branchial or 

 epibranchial sense organ], though differentiated, is a larval structure only, and disappears 

 in the adult." Finally Wilson and Mattocks (1897, 226) confirm for Salmo the discovery 

 already made by the former author in Serranus of a common anlage of the lateral and 

 auditory sense organs, and state further that the portion in front of the auditory saucer 

 gives rise by bifurcation to the supra- and infra-orbital canals, whilst the portion posterior 

 to the saucer grows backwards and forms the lateral canal. 



We thus see that the metamerism of the lateral line nerves and their associated sense 

 organs has for a long time been a problem, the solution of which has been attended with 

 considei-able difficulties. The older anatomists considered the nerves to be branches 

 of the trigeminus, facialis, and vagus, until it was shown by Priant in 1879 that the 



* But cp. ])p. 4!l2 and 50], which go to show thai Beaid"s branchial sense organs do not belong to the lateral line 

 system. 



