THE EVIDENCE OF THE AUDITORY APPARATUS 379 
admits the passage not only of the auditory and facial nerves, but 
also of a portion of the peculiar tissue which surrounds the brain. 
The large cells of this tissue, with their feebly staining nuclei and 
the pigment between them, make them quite unmistakable; and, as 
T have already stated, nowhere else in the whole of Ammoccetes is 
such a tissue found. When I first noticed these cells within the 
auditory capsule, it seemed to me almost impossible that my inter- 
pretation of them as the remnant of the generative and hepatic tissue 
which surrounds the brain of animals such as Limulus could be true, 
for it seemed too unlikely that a part of the generative system could 
b) 
gen hi hI gen 
Fic. 154.—TRANSVERSE SECTION THROUGH AUDITORY CAPSULES AND BRAIN OF 
AMMOCGTES, 
Au., auditory organ; VIII, auditory nerve; gl., ganglion cells of VIIIth nerve; 
lu. cart., cartilaginous auditory capsule; gen., cells of old generative tissue 
round brain and in auditory capsule; 0/., blood-vessels. 
ever have become included in the auditory capsule. Still, they are 
undoubtedly there; and, as already argued with respect to the 
substance round the brain, they must represent some pre-existing 
tissue which was functional in the ancestor of Ammoccetes. If my 
interpretation is right, this tissue must be generative and hepatic 
tissue, and its presence in the auditory capsule immediately becomes 
a most important piece of evidence, for it proves that the auditory 
organ must have been originally so situated that a portion of the 
generative and hepatic mass surrounding the cephalic region of 
the nervous system followed the auditory nerve to the peripheral 
sense-organ. 
