Bibliography.
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[194] The function of the otoliths is not always clear. There is evidence to shew that they sometimes act as dampers.
[195] For the somewhat complicated details as to the development of the auditory sacks of Cephalopods I must refer the reader to Vol. II., pp. 278, 279, and to Grenacher (Vol. I., No. 280).
[196] It is not clear from Böttcher’s description how it comes about that the inner rods of Corti are more numerous than the outer.
[197] The organs which resemble those of the lateral line are the remarkable sense organs found by Eisig in the Capitellidæ (Mittheil. a. d. Zool. Station zu Neapel, Vol. 1); but I am not inclined to think that there is a true homology between these organs and the lateral line of Vertebrata. It seems to me probable that the segmentally arranged optic organs of Polyophthalmus are a special modification of the more indifferent sense organs of the Capitellidæ. The close affinity of these two types of Chætopods is favourable to this view.
[198] Götte and Semper both hold that the lateral nerve, instead of growing in a centrifugal manner like other nerves, is directly derived from the epiblast of the lateral line. For the reasons which prevent me accepting this view I must refer the reader to my Monograph on Elasmobranch Fishes, pp. 141-146.