148 STRONG. [Vol. X. 



remarkable richness. It is not unlikely that the appearances 

 may be exaggerated by inequalities of impregnation, but in 

 Golgi preparations all of this epithelium presents pictures 

 remarkably rich in nerve fibres. We have seen above (p. 124) 

 that the glands in this region are so numerous as to be prac- 

 tically continuous and not separated by indifferent epithelium. 

 In such places the superficial nerve plexus belonging to these 

 glands and described above (pp. 125, 126), naturally is also con- 

 tinuous, and there is consequently a dense plexus extending 

 throughout the superficial part of this epithelium. Its general 

 appearance is indicated in PI. IX, Fig. 23, and is still more dense 

 in preparations from a larger and probably older specimen. 



The greater part of the filtering apparatus, and also the gills, 

 are innervated by the Rr. branchiales. There is a great differ- 

 ence in my preparations between the innervation of these two 

 structures. While in the former are demonstrated a great 

 number of fibres, very few are shown in the gills proper. 

 These latter fibres are very delicate and cannot usually be 

 followed very far into the gills. They proceed along with the 

 blood vessels and seem to be vaso-motor. It is not improbable 

 that the fibres in gills do not impregnate readily, and that the 

 supply is greater than the preparations would indicate. 



Into the filtering apparatus bundles of fibres pass upward 

 from the Rr. branchiales. These pass along in the loose con- 

 nective tissue in the interior of these structures, send fibres 

 into the smaller subdivisions, or side-pockets, and fill these 

 with a snarl or tangle of fibres (PI. VIII, Fig. 9). Endings 

 are frequently seen on these fibres in the shape of small gran- 

 ules, or sometimes, apparently, several granules. Sometimes 

 the two granular terminations of two fibres seem to meet each 

 other {Xy Fig. 9). Very often these terminations are in the 

 very outer surface of the filament of the filtering apparatus. 

 The fibres do not usually, at any rate, anastomose. 



These gill filters, together with the glandular epithelium 

 described above, evidently form an important apparatus, physi- 

 ologically. There would seem to be a physiological similarity 

 between these glands and those on the endostyle of Amphi- 

 oxus. 



