HALCYONELLEA : ALCYONIDIUM. 361 



and in Trans. Newc. Soc. ii. 251, pi. 9, fig. 1. Alcyonidium hirsutum, Johns. 

 Brit. Zooph. 303, pi. 42, fig. 1, 2. //assert in Ann. and Mag. N. Hist. vii. 370, 

 pi. 10, fig. 3,4. Couch Corn. Faun. iii. 1 33. Halodactyle velu, Van Beneden 

 Recherch. 61, pi. 8, fig. 3-8. 



Hob. Parasitical on various sea-weeds at low water-mark, common. 



Polypidom variously divided, often proliferous, sometimes sub-cy- 

 lindrical, commonly flattened and palmate, of a dirty straw-yellow 

 colour, often partially stained with red, and marked with numerous 

 yellowish circular spots irregularly disposed. It is thickish, some- 

 what cartilaginous, and to the naked eye resembles a compact sponge. 

 When viewed through a common magnifier, the surface is seen to be 

 covered with close-set conical transparent papillje, each of which is a 

 cell containing a polype with sixteen long filiform tentacula, and in its 

 structure resembling the polype of a Flustra. The yellowish spots, 

 mentioned in the description, are produced by clusters of ova lying 

 embedded in the cellular texture. These are opaque, milk-white, 

 large enough to be easily visible to the eye, of a roundish figure, but 

 not all of them alike, for some are ovate, and others incline to a 

 heart-shape, rather compressed, the surface uneven. The egg is 

 clothed with cilia, of equal size and shape, and all inclined in one 

 direction, moving with a uniformity and quickness which is ad- 

 mirable and very pleasing to the beholder. When the egg is at rest, 

 their velocity is not diminished, excepting at the will, so to speak, of 

 the ovum, for it may be seen to become slower and less constant, to 

 cease entirely for a moment, and again be renewed with its for- 

 mer force. The egg at rest will at once start from its place, and 

 swim about hither and thither as it were endowed with volition, 

 turning on its axis frequently, moving sometimes on one side, some- 

 times on its edge, when the cilia become invisible. I have seen the 

 cilia, when the ovum was at rest, suddenly disappear, withdrawn as 

 it seemed within themselves, and again be quickly protruded. By 

 their motion they drive a current of water over the surface ; but this 

 current has certainly not an uninterrupted circular motion it is 

 rather a flowing to the surface, and a current from it, or, as Raspail 

 would express it, an inspiration and expiration of water. When 

 lying still, I have seen the eggs exhibit the most unequivocal signs 

 of irritability, contracting and dilating themselves. The ovum ap- 

 pears to be formed of a firm elastic coat or shell filled with a granular 

 matter. 



The Spongia damicomis of Esper, Pflanz. Spong. tab. 63, is appa- 

 rently the Alcyonidium hirsutum. 



