THE EVIDENCE OF THE AUDITORY APPARATUS 3°73 
is the cause of the ill-defined appearance of the central pore, just 
as the terminal pore is much less conspicuous on surface-view in the 
spike-organs of the flabellum than in the purely poriferous organs, 
no part of which projects beyond the level of the chitinous surface, 
The fine tubule is soon lost in the thickened but soft modification 
of the chitinous layer (ch.) which is characteristic of the sense-organ ; 
at all events, I have not succeeded in tracing it through this layer 
with any more success than in the corresponding case of the tubules 
Fra. 152.—A, SECTION THROUGH TooTH OF PECTEN OF ScoRPIoN; B, SuRFAcE VIEW 
or SznsE-OrGans; C, GosLet or SENsSE-ORGAN MORE HIGHLY MAGNIFIED. 
bi. and n., region of blood-spaces and nerves; gl., ganglion-cell layer; ch,, modified 
chitinous layer; s.0., sense-organ. 
belonging to the smaller goblets of the branchial sense-organ of 
Limulus already described. 
At the base of the modified chitinous layer a series of cells is 
seen, many, if not all, of which belong to the chitinogenous layer. 
Next to these is the marked layer of ganglion-cells (g/.), similar to 
those seen in the flabellum of Limulus, The rest of the space in the 
section of the tooth is filled up with nerves (n.) and blood-spaces (1.) 
just as in the section, Fig. 146, of the flabellum of Limulus. 
Gaubert does not appear to have seen the goblets at all clearly ; 
