264 Prof. P. M. Duncan on the 



In 1864 Huxley noticed that, with regard to the Ccelenterata, " a ner- 

 vous system has at present been clearly made out only in the Cteno- 

 phora"*. 



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

 Actinozoa in 1851. He corrected Erdl's mistake concerning the sup- 

 posed striation of the muscular fibrillaB of the tentacles, and also Quatre- 

 fage and Leuckart's notion concerning the rupture of the tentacular ends 

 previously to the passage of water from them. Giving very good illus- 

 trations, 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 calicinales." These bead-like appendages, 

 situated just without the tentacles in some genera, but not in all, are 

 also called chromatophores and " bourses marginales ; " and their beautiful 

 turquoise colour had rendered them attractive to previous anatomists, 

 who had, as has already been noticed, guessed concerning their function. 



Homard determined that they were folded elements of the skin in 

 which the capsules' (nematocysts) were enormously developed. He 

 stated that the thread of these gigantic nematocysts was seen with diffi- 

 culty. He noticed the transparency of some large cells in the bourses, 

 and stated that, in his opinion, there was " some physiological relation be- 

 tween these little organs and the light." 



Jules Haime (probably in 1855) examined the minute anatomy of 

 Actinia mesembryanthemum, and his colleague, Milne-Edwards, quotes 

 him in the ' Hist. Nat. des Coralliaires/ vol. i. p. 240. The lamented 

 young naturalist found out that the chromatophores bore, so far as their 

 number is concerned, a decided numerical relation with the number of 

 the tentacles. He decided that they contained but few muscular fibres, 

 and had navicular-shaped uematocysts, " diversernent contournes," with 

 indistinct threads within them. However, he recognized large trans- 

 parent cells and pigmentary granules in them. The nematocysts of the 

 chromatophores are larger than those of the tentacles. He was evi- 

 dently not satisfied with the data upon which these coloured masses were 

 decided to be of importance as organs of special sense. In all probability 

 Haime was aware of Homard's work. 



Kolliker and the German histologists added about this time, and later, 

 to the exact knowledge respecting the histology of the muscles, skin, 

 endothelium, and tentacular apparatus, but no advance was made to- 

 wards the discovery of a nervous system in the Actinia for many 

 years. 



In 1871 the popular idea of the extent of the nervous system in 



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

 on Beroe pileus, Zool. Trans, vol. i. p. 10. See also ' A Manual of the Subldngdom 

 Ccelenterata,' by J. E. Greene, 1861, p. 1G5. 



f "Sur les Actinia:," Ann. des Sciences Nat. 1851. 



\ Sea-side Studies, Eliz. and A. Agassiz, 1871, p. 12. 



