NERVOUS SYSTEM OF ARTICULATA. 485 



slender nervous filaments are sent off to the head, 

 and others to the eyes ; and a larger branch to the 

 abdominal surface of the body. The discovery of 

 a regular structure of muscular bands of fibres, 

 in these animalcules, is a further evidence of 

 the connexion which exists between nerves and 

 muscles. 



It is doubtful whether the Actinia possesses these 

 organs; although Spix conceived that he had traced 

 ganglia and nervous filaments in connexion with 

 the mass of muscular fibres situated in the base or 

 sucking disk of this animal ;* but it is now gene- 

 rally believed that he was mistaken, as every suc- 

 ceeding; observer has searched for them in vain. 

 Professor Rymer Jones, however, describes a deli- 

 cate thread, which he detected passing round the 

 roots of the tentacula, embedded in a strong cir- 

 cular band of muscle, surrounding the orifice of 

 the stomach, and acting as a powerful sphincter in 

 closing the aperture-t 



In the larger species of ^ledusce, Ehrenberg 

 found two nervous circles contained in the disk ; 

 one passing along the margin of the mantle, and 

 traversing eight minute ganglia, wdience there pro- 

 ceed filaments to the same number of red spots 

 wdiich he supposes to be eyes ; and the other, sur- 

 rounding the entrance into the stomach, and fur- 

 nished with four ganglia, from which the four 

 tentacula are supplied with nervous filaments. A 

 similar apparatus was found by Dr. Grant in the 

 Cydippe pilens, a species of Beroe.j 



* Annales du Museum, xiii. 439. 



t Outline of the Animal Kingdom, p. 43. 



t Trans. Zool. Soc. i. 10. 



