THE EVIDENCE OF THE AUDITORY APPARATUS 375 
not closely resemble the majority of the end-organs of the flabellum, 
yet it does resemble, on the one hand, the isolated poriferous spikes 
found on the flabellum (Fig. 149) and, on the other, the poriferous 
goblets found on the sense-patches of the branchial appendages of 
Limulus (Fig. 144, A), so that a combination of these two end-organs 
would give an appearance very closely resembling that of the pecten 
of the scorpion. 
Finally, the special so-called ‘ racquet-organs’ of Galeodes, which 
are found on the most basal segments of the last pair of prosomatic 
appendages, ought also to be considered here. Gaubert has described 
their structure, and shown how the nerve-trunk in the handle of the 
racquet splits up into a great number of separate bundles, which 
spread out fan-shaped to the free edge of the racquet; each of these 
separate bundles supplies a special sense-organ, which terminates 
as a conical eminence on the floor of a deep groove, running round 
the whole free edge of the racquet. This groove is almost converted 
into a canal, owing to the projection of its two sides. Gaubert 
imagines that the sense-organs are pushed forward out of the groove 
to the exterior by the turgescence of the whole organ; each of the 
nerve-fibres forming a bundle is, according to Gaubert, connected 
with a nerve-cell before it reaches its termination. 
This sketch of the special sense-organs on the appendages of 
Limulus, of the scorpions, of Galeodes, and other arachnids, and their 
comparison with the porous chordotonal organs of insects, affords 
reason for the belief that we are dealing here with a common group 
of organs, which, although their nature is not definitely known, 
have largely been accredited with the functions of equilibration and 
audition, a group of organs among which the origin of the auditory 
organ of vertebrates must be sought for, upon any theory of the 
origin of vertebrates from arthropods. 
Whenever in any animal these organs are concentrated together 
to form a special organ, it is invariably found that the nerve going to 
this organ is very large, out of all proportion to the size of the organ, 
and also that the nerve possesses, close to its termination in the 
organ, large masses of nerve-cells. Thus, although the whole hind 
wing in the blow-fly has been reduced to the insignificant balancers 
or ‘halteres,’ yet, as Lowne states, the nerves to them are the largest 
in the body. 
The pectinal nerve in the scorpion is remarkable for its size, and 
