XIV SENSE-ORGANS : 389 
outer surfaces of the fibrous membranes which close a pair of 
vacuities in the outer bony walls of the periotic capsules, the 
inner surfaces being bathed by the perilymph surrounding 
the auditory organs. This method is characteristic of certain 
Serranidae, Berycidae, Sparidae, Gadidae, and Notopteridae,’ and 
probably in the Hyodontidae. In the second method, of which 
several Clupeidae (e.g. Herring, Pilchard, etc.) furnish examples, 
the periotic vacuities are open in- 
stead of closed, and the sac-like 
ends of the tubular extensions 
from the air-bladder are in actual 
contact with protruding outgrowths 
from the utriculus.2 The third 
method, by far the most elaborate, 
is by the intervention of a series 
of movably connected “ Weber- 
ian” ossicles, of which the most 
posterior on each side (the tripus) 
is inserted into the dorsal wall of F's. Aer of the eee of 
a 0 < os a Siluroid (Wacrones nemurus) ex- 
the air-bladder (Fig. 223), while posed by the removal of its ventral 
fieranmkeniorone:(scaphium) forms ll 2c, Anterior chamber 5 b.o, 
E basioccipital ; b.w, body wall, here 
the outer wall of a median back- reduced to the external skin; 
ward prolongation (sinus impar) cel, clavicle; ¢.c, lateral chamber ; 
. ae Z.s, longitudinal septum , pt, post- 
of the perilymph-containing spaces temporal; ¢r.v, anterior portion of 
: a) the tripus ; ¢7.c, crescentic portion 
ay Oo od « Vy ’ > 
surrounding the two auditory Gf the Ripe a Bar taney eROeee 
organs. This in turn encloses a tum; ¢.s’, shorter transverse sep- 
His oF, . . tum. (From Bridge and Haddon.) 
similar median prolongation (sinus 
endolymphaticus) from the two sub-cerebrally united endo- 
lymphatic ducts (Fig. 223).° This complex mechanism is present in 
the Cyprinidae, Siluridae, Characinidae, and Gymnotidae; and hence 
the term “ Ostariophysi ” * as a collective name for these families.” 
Bridge, Journ. Linn. Soc. xxvii. 1900, p. 503. 
Ridewood, Journ. Anat. and Phys. xxvi. 1892, p. 26. 
E. H. Weber, De aure ct auditu Hominis et Animalium. Parsi. De aure 
Animalium Aquatiliwm, Leipzig, 1820; Bridge and Haddon, Phil. Trans. 184, 
1893, p. 65. 
4 Sagemehl, Morph. Jahrb. x. 1885, p. 22. 
> The Weberian ossicles are modified components of certain of the anterior 
vertebrae. Thescaphium represents the neural arch of the first vertebra ; the inter- 
calarium is the arch of the second vertebra; while the tripus is probably the rib 
of the third vertebra. In the Characinidae and the Cyprinidae an additional 
ossicle, the ‘‘claustrum”’ is present. 
EI 
2 
3 
