66 On the Nervous System of Actinia. 



loped sensibility ; not only do they contract forcibly upon the slightest 

 touch, but they are, moreover, not insensible to the influence of 

 light. Nevertheless, neither a nervous system nor organs of special 

 sense have been discovered in them. It is true that Spix described 

 and figured ganglions and nervous cords in the pedal disk of 

 Actiniae ; but the observations of this naturalist, so far as the polypes 

 are concerned, are not entitled to the least confidence. 



" Some naturalists have supposed that the ' bourses calicinales ' 

 of the Actiniae are eyes, and M. Huschke believes that certain 

 capsules in the trunk of Veretilla, which contain calcareous bodies, 

 are the organs of hearing. But these hypotheses do not rest upon 

 any proved facts." 



In 1864 Huxley noticed that, with regard to the Coelenterata, 

 " a nervous system has at present been clearly made out only in 

 the Ctcnophora." * 



Homard, t an admirable observer, contributed to the histology of 

 the Actinozoa inl 1851. He corrected Erdl's mistake concerning 

 the supposed striation of the muscular fibrillae of the tentacles, and 

 also Quatrefages and Leuckart's notion concerning the rupture of 

 the tentacular ends previously to the passage of water from them. 

 Giving very good illustrations, he proved himself to be a very 

 reliable investigator. 



Amongst other parts of the Actinozoa, he paid especial attention 

 to the minute anatomy of the " bourses cahcinales." These bead-like 

 appendages, situated just without the tentacles in some genera, but 



Fig. 12. — Three portions of intermediate tissue ending in the layer of granular 

 cells wliich underlies the Rottcken bodies. 

 „ 13. — Haiinean and EiJtteken bodies and the intermediate tissue in position. 

 „ 15. — A diagram, but very close to natiu-e, of the relative position of the histo- 

 logical elements of the chromatophores. 

 „ 16. — Haimean and Eotteken bodies intermingled. 



„ 17. — Haimean bodies surrounded by pigment cells, and with bacilli flat upon 

 them, owing to jjressure. 

 Figs. 18 and 19, — Fusiform nerve cells. 

 Fig. 20.— a nerve cell. 

 „ 21. — Nerve cells connected and with fibres. 

 „ 22. — A spherical nerve cell with processes joining the plexus. 

 „ 23. — Ramifications of the plexiform cord. 

 „ 24. — Nerve cell and fibres. 



Plate LXX. 



„ 25. — Nerve in relation to the small muscular fibrils of the base. 



„ 26. — Nerve ramifying and supplying wide muscular fibre. 



„ 27. — A loop of nervous fibre. 



„ 28. — Terminal ends of the plexus passing over muscular fibre. 

 Figs. 29 and 30. — The same, more highly magnified. 

 Fig. 31. — The plexus under the endothelium. 



* Huxley, ' Elements of Comparative Anatomy,' p. 82. See Dr. Grant, F.R.S., 

 &c., on Beroe pileus, 'Zool. Trans.,' vol. i., p. 10. See also ' A Manual of the Sub- 

 kingdom Cceleuterata,' by J. R. Greene, B.A., 1861, p. 165. 



t " Sur ks Actinia)," ' Ann. des Sciences Nat.,' 1851. 



