118 THE AQUARIAN NATURALIST. 



opens wide for the admission of food. The tentacula 

 are comparatively very short. They sometimes ap- 

 pear to consist of a stout stalk and globular head, 

 which form, however, is merely the result of con- 

 traction, for there is no appearance of this globosity 

 in the active and vigorous polyps. The stalk is solid 

 and colourless, tapered gently upwards, and coated 

 with a very thin and faintly wrinkled skin, while the 

 head is white or faintly coloured, and muricated or 

 roughened with sharp points. Mr. Lister says that 

 it is covered with short projections like blunt hairs, 

 and it seems to be by their means that the polyps 

 attach with a touch, or release at will, substances that 

 drift within their reach. According to Mr. Hassall, the 

 murications seem to be "minute cups, similar to those 

 of the cuttle-fish." This discrepancy Dr. Thompson 

 ascribes to the different manner in which probably 

 the observations upon the organs in question have 

 been made. Lister's description accords well with 

 what is observed when the head is seen at freedom, 

 and the appearance of cups is only produced when 

 the animal is viewed compressed between plates of 

 glass. The granules or blunt hairs appear to be of a 

 glandular nature, secreting a tenacious mucus. When 

 brought in contact with a foreign body, the tentacula 

 instantly adhere to it with sensible firmness, and the 

 act is too instantaneous to be the result of the appli- 

 cation of suckers, or of any power dependent on mus- 

 cular action. But sometimes a film or line may be 

 seen stretched between the foreign object and the 

 head of the tentaculum, when this is naturally with- 

 drawn by the animal itself. 



