See previously cited papers by Herrick and Cole; also Ewart, Trans. Roy. Soc. Edinb. xxxvi. 1892, p. 59; Collinge, Quart. Journ. Micr. Sci. xxxvi. 1894, p. 499; and Herrick, Journ. Comp. Neurology, xi. 1901, p. 177.
Allis, Journ. Morph. ii. 1889, p. 463.
Johnston, Journ. Comp. Neurology, xii. 1902, p. 2.
Fuchs (Archiv f. d. ges. Physiol. lix. 1895, p. 454) has suggested that these organs may be concerned with the perception of pressure variations. It has also been argued that they are concerned with equilibration and the co-ordination of the movements of the fins. (See American Journ. Physiol. i. p. 128.)
Burckhardt, Das Central-Nervensystem v. Protopterus, Berlin, 1892, p. 32.