Nervous System of Actinia, 265 



Actinia was expressed by Alex. AgassizJ, who wrote: "Notwithstanding 

 its extraordinary sensitiveness, the organs of the senses in the Actinia 

 are very inferior, consisting only of a few pigment-cells accumulated at 

 the base of the tentacles." 



But in this year a great advance was made towards discovery by 

 Profs. A. Schneider and Botteken*. The first-named naturalist paid 

 especial attention to the development of the lamellae and septa in Corals 

 and Actiniae, and his colleague laboured in the histology of Actinia 

 especially. 



"Working at a very great disadvantage, with specimens which had been 

 preserved in alcohol, Botteken produced a series of researches which 

 added greatly to the knowledge already granted to science by Homard and 

 Haime. So far as they bear on the nervous system, the result of his re- 

 searches may be stated as follows : " The bourses marginales " (chroma- 

 tophores) are undoubtedly organs of sense, and, indeed, compound eyes. 

 They are pyriform diverticula of the body-w T all, standing between the 

 tentacles and the outer margin of the peristome ; they are constructed 

 after the fashion of a retina, and the following layers of structure may be 

 distinguished in them : 1, externally a cuticular layer broken up into 

 "bacilli" by numerous pore-canals; 2, a layer of strongly refractile 

 spherules, which may be regarded as lenses ; 3, cones hollow, strongly 

 refractile, transversely striated cylinders or prisms rounded at the ends ; 

 these have hitherto been confounded with urticating capsules (nemato- 

 cysts) : at the exterior end of each cone there is generally one lens, and 

 sometimes two or three may stand in the interspaces ; 4, a granular 

 fibrous layer occupying the interspaces between the cones ; 5, a layer 

 which is deeply stained by carmine, and contains numerous extremely fine 

 fibres and spindle-shaped cells, probably nerve-fibres and cells ; 6, the 

 muscular layer ; 7, the endothelium, which bounds the perigastric cavity. 



Actinia mesembryanthemum was the species examined, and the diagram 

 (PL II. fig. 15) will explain the relative position of the layers. 



Botteken could not determine the position of the pigment of the 

 chromatophores from the alcoholized specimens. An examination of the 

 minute anatomy of the tentacles of Actinia cereus, Ellis and Solander, 

 determined that the refractile spherules and large cones were to be found 

 on the tips of these organs. 



Danat, in his popular work on Corals and Coral Islands, appears to 

 accept the statements quoted above. He states that " they sometimes 

 possess rudimentary eyes ;" and elsewhere, " they have crystalline lenses 

 and a short optic nerve." He then observes : " Yet Actiniae are not 



* Sitzungsbericht der Oberhessischen Gesellschaft fiir Natur- und Heilkunde, March 

 1871 (On the Structure of Actiniae and Corals). Translated for the Ann. and Mag. of 

 Nat. Hist, 1871, vii. p. 437, by W. S. Dallas, F.L.S. &c. 



t Corals and Coral Islands, by Juiues D. Dana, LL.D., 1872, pp. 41, 39. 



