320 



MOLLUSCA 



[CH. 



superior and inferior, each representing a pair fused together, they 

 are joined by a minor nerve collar running round the oesophagus. 

 The inferior ganglion corresponds to the buccal pair in the snail, the 

 superior is a separated part of the cerebral. 



18-- 



13 



- 20 



14 



FIG. 148. Sepia qfficinalis dissected to show the nervous system, ventral view. 



From Cher on. 



1. Three nerves to the arms dissected out. 2. Auditory nerve. 3. Anterior 

 nerve to the funnel. 4. Nerve to vena cava. 5. Posterior nerve 

 to funnel. 6. Continuation of this nerve. 7. Accessory nerve to 

 mantle. 8. Left nerve to mantle. 9. Stellate ganglion. 10. Com- 

 mon trunk of the visceral loop. 11. Left branch of the visceral loop. 

 12. Nerve to muscles. 13. Nerve to viscera. 14. Ganglion on 

 branchial heart. 15. Nerve of ctenidium. 16. Ink-sac. 17. Duct 

 of ink-sac. 18. Left nidamental gland. 19. Branchial heart. 

 20. Position of anus. 21. External opening of kidneys. 



It has been already stated that Sepia possesses complicated eyes. 

 In the embryo these, like the eyes of the snail, are merely sacs lined 

 by visual cells and containing a transparent horny secretion which 

 serves as a lens. In fact, in the embryo, the sac is at first a pit 



