206 THE MICROSCOPE. 



" Each plume," says Mr. Lister, in reference to a specimen of this 

 species, "might comprise from 400 to 500 polyps;" "and a specimen," 

 writes Dr. Johnston, " of no unusual size, before me, has twelve plumes, 

 with certainly not fewer cells on each than the larger number men- 

 tioned; thus giving 6000 polyps as the tenantry of a single polypidom ! 

 Now, many such specimens, all united too by a common fibre, and all 

 the offshoots of one common parent, are often located on one sea-weed, 

 the site then of a population, which nor London nor Pekin can rival." 



Plumulatia pinnata, or Feather Polyp (represented magnified in 

 Plate I. No. 3), " is as remarkable for the elegance of its form, as its 

 likeness to the feather of a pen." It serves not among the denizens of 

 the deep the same purpose as its earthly prototype. Nature writes her 

 works in hieroglyphics formed by the objects themselves. It is plumous, 

 and the cells in a close row, cup-like, and supported on the under side 

 by a lengthened spinous process. 



An interest pervades the valuable work of Dr. Johnston, arising 

 from the circumstance that the plates and woodcuts which adorn the 

 volume are, with few exceptions, engraved from drawings made for it 

 by Mrs. Johnston, who also engraved several of them ; and the Doctor 

 states he could not have undertaken the history without such assist- 

 ance. From this devotion to, and understanding of the subject, it was 

 natural, when an opportunity presented itself, to write in the catalogue 

 of Zoophytes a lasting memorial of his " colleague :" and thus is written 

 the graceful compliment of the beautiful " Plumularia Catharina : 

 whose stem is plumous, pinnae opposite, bent inwards ; cells distant, carn- 

 panulate, with an even margin ; vesicles scattered, pear-shaped, smooth. 

 Found on old shells, corallines, and ascidia, in deep water. At Scar- 

 borough it is rare. In Frith of Forth by Dr. Coldstream, and fre- 

 quently in Berwick Bay. This equals P. pinnata in size and delicacy, 

 but differs from it very obviously in having opposite pinna?, which, in- 

 stead of being arched, are bent inwards, so as to render the general form 

 of the coralline concave on a front view ; an appearance produced by 

 the pinna3 originating, not from the sides, but from the anterior face of 

 the stein. The stem itself is straight or slightly bent, jointed, pellucid, 

 filled with a granular fluid matter ; and in which it differs from its con- 

 geners, bearing cells, there being always one at the base and between 

 the insertion of the pinna?, and generally another on the interval be- 

 tween them. Between the cells there is a series of minute tubular or 

 tooth-like cells, visible only with a high magnifier. The ovarian vesicles 

 are produced in summer ; they are stalked, shaped like a pear or vase, 

 solitary, scattered, and originating always at the base of a polyp cell. 



