10 THE ZOOLOGIST. 



rences between the fully expanded polyps and the shrunken 

 apertures into which they have disappeared lack tone. It is 

 rare to find one collected by hook, dredge, or trawl in a satis- 

 factory condition — indeed, such has never been seen. The only 

 method of securing a perfect example is, as stated in 1864,* by 

 searching for small specimens near low- water mark under 

 stones, chipping them carefully with a basis of stone, and at 

 once placing them in sea-water. Thus a patch three-quarters 

 of an inch in diameter contracted to one-tenth of an inch in 

 thickness. "As the polyp contracts into its stellate aperture its 

 mouth gapes, apparently the more readily to give exit to the 

 water in its interior. It presents the aspect of an octagon with 

 hollow sides when about the level of its cell. Hows of spicula 

 project from the corners towards the centre. If further extended 

 the tentacula, their pinnae, and the rows of spicula become 

 more apparent ; oral aperture dilated ; outline of oral disc 

 similarly octagonal, though much larger. When still further 

 extended, coiling of the arms is frequently seen, like the circi- 

 nate vernation of the ferns. In a state of full expansion the 

 polyp is elongated and narrowed toward the head, measuring 

 more than half an inch from the tips of the tentacula to the base. 

 The tentacles can be stretched to more than twice the diameter 

 of the oral disc, are narrow and tapering, and have the elongated 

 pinnae at each side ; the tips are slightly opaque, probably from 

 minute suckers. The tentacles are also rendered rough by 

 minute spicula, which do not, however, go further than the 

 base, where a pale non-spicular portion occurs ; below this the 

 neck of the polyp is supplied with long tuberculated spicules, 

 arranged in an arrow-like manner. In those polyps which are 

 best expanded the diameter of the oral disc is smallest. Some- 

 times, from the position of the parts, the tentacle with its pinnae 

 presents a spindle-shaped appearance. "t The spicules of the 

 tentacles appear to have had but little attention paid to them, 

 though they are figured by Prof. Hickson in his Memoir (vol. 37, 

 fig. 10), and alluded to on p. 370.1 



* Proc. Koy. Soc. Edin. vol. v. p. 393, 1862-66. 



f An accurate drawing of this example by the late Mrs. Giinther is given 

 in ' The Marine Invertebrates and Fishes of St. Andrews,' pi. vii. fig. 8, 1875. 

 | Op. cit. 



