524 THE MICROSCOPE 



of the deep, found usually on old shells, an inch in height, 

 spreading itself fan-like, and of an ashy colour, deeply 

 divided in a dichotomous manner into narrow, thin, plane 

 segments, truncate at the end, formed of four or five series 

 of oblong cells, capped with a hollow, globose, pearly, oper- 

 culum seated between the spines, of which there is one on 

 either side of the circular aperture. The opercula are so 

 numerous, that they give to the upper surface tbe appear- 

 ance of being thickly strewn with orient pearls ; the under- 

 surface is even and longitudinally striated, the number of 

 strife corresponding to the number of rows in which the 

 cells are disposed. Dr. Johnston describes, amongst many 

 other British species, F. membranacea, " a gauze-like incrus- 

 tation on the frond of the sea-weed, spreading irregularly 

 to the extent of several square inches." 



Dr. Perceval "Wright discovered on the western coast of 

 Ireland a new genus of Alcyonidce, which he named after 

 the well-known naturalist ]\fr. Harte, Hartea elegans, Plate 

 IV. lio. 86. This polype is solitary, the body cylindrical, 

 and fixed by its base to the rock; it has eight ciliated 

 tentacles, which are knobbed at their base and most freely 

 displayed. It is a very beautiful polyzoon of a clear white 

 colour, and when fully expanded stands three-quarters of 

 an inch high. 1 



The fresh-water Polyzoa are peculiarly interesting ob- 

 jects for microscopic observation, from the very beautiful 

 manner in which they display their ciliated tentacula, set 

 upon a crescentic, horseshoe-shaped "lophopore." The 

 arrangement of the latter appendage has been the cause of 

 separating the fresh-water Polyzoa, from their marine 

 allies, into a sub-class ; the former being named Hippocrepa 

 (horseshoe-like), and the latter Infundibulata (funnel- 

 like). 2 The most striking form among the Hippocrepa is 

 the Cristatella Macedo — a wandering Polyzoon, capable of 

 moving freely through the water. It may be met with 

 during a great part of the summer in our ponds and streams, 

 amidst the stems and leaves of aquatic plants (Plate IY. 



(1) On a new genus of Alcyonidce. By Dr. E. Perceval Wright. Micros. 

 Journ. Science, vol. v. p. 213. 1SG5. 



(2) The reader is referred to a valuable treatise on the structure and classifi- 

 cation of this group by Professor Allman, Monograph of the British Fresh' 

 water Polyzoa, published by the Ray Society, 1S57. 



