CELLEPORIDJE. 517 



at the base of the tentacles, and others lower down the 

 body of the polype." 



When we consider the minuteness of the delicate little 

 sprig which is the natural size of this polype, we cannot 

 but wonder at the triumphs of the microscope in giving 

 such precise details as Mr. Busk relates of the Notamia 

 bursaria. Its beautiful and perfect organisation, the care- 

 ful provision for the safety and engagements of this 

 minute being, make us awe-stricken at the power of Divine 

 intelligence. 



The Halodactylus, better known as Alcyonidium, is re- 

 markable among the marine forms of Polyzoa, for the large 

 size of its tentacular crowns; these when expanded are 

 distinctly visible to the unassisted eye, and present a spec- 

 tacle of great beauty when viewed with the binocular 

 microscope. Its polyzoary has a spongy aspect very much 

 resembling that of the Alcyonian zoophyte : when how- 

 ever the animals are expanded, they are at once seen to be 

 widely different, as the plumose turfts which then issue 

 from the surface of Halodactylus give it the appearance of 

 a beautiful downy film. The opacity of its polyzoary 

 renders it unsuited for the examination of anything more 

 than the tentacular crown. 



Lepralia, " Sea-scurf," from the Greek for marine 

 leprosy, is the name given to this family of the Celle- 

 poridce by Dr. Johnston. 



Lepralia nitida, found attached to shells, is thus 

 described : " Crust spreading circularly, closely adherent, 

 rather thin, greyish white, calcareous ; cells contiguous, 

 in radiating rows, large, subalternate, ovate, ventricose, 

 silvery, the walls fissured with six or seven cross slits 

 which are on the mesial line ; aperture subquadrangular, 

 depressed, terminal ; anterior to it there is often found a 

 globular, pearly, smooth, oviferous operculum, with a round 

 even aperture. The remarkable structure of the cells 

 renders this one of the most interesting species under the 

 microscope. There is sometimes an appearance of a spine 

 on each side of the lower angle of the mouth, which is 

 merely the commencement of the walls of the next cell.** 



L. coccinea, L. variolosa, L. ciliata, L. t>~ispinosa, and 

 L. immersa, are the other British species. 



