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 

 I 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 braiu of animals such as Limulus could be true, 

 for it seemed too unlikely that a part of the generative system could 



vin 



. -Au car I 



pen hi 1,1 gen 



Fig. 154. — Transverse Section through Auditory Capsules and Brain op 



Ammoccetes. 

 Au., auditory organ; VIII, auditory nerve; rjl., ganglion cells of Vlllth nerve; 



Au. cart., cartilaginous auditory capsule; gen., cells of old generative tissue 



round brain and in auditory capsule ; bl., 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 Ammocretes. 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. 



