ZOOPHYTES. 251 



parence of the body, which is scarcely darker than the surrounding 

 element. 



This product is founded either independently on shells, or it grows as 

 a parasite on other zoophytes. It is frequently so closely interwoven with 

 a variety of matter, as to render the extrication of specimens entire a very 

 difficult task. 



I have never seen the cells of any specimen ranged in a straight line 

 as a single series, nor otherwise than alternately. 



Plate LII. Fig. 1. Valkeria Undigera, 



2. The same enlarged. 



3. Another specimen. 



4. Arrangement of the cells, enlarged. 



5. Hydra enlarged. 



§ 4. Valkeria spinosa. — Silk Coralline. — Plate LI. Figs. 3, 3. — This 

 is a fine and elegant product, of the most delicate texture. It rises seve- 

 ral inches in height, bounded for the most part by what might be the form 

 of a narrow cylindrical vessel, containing a living specimen. But the parts 

 are so numerous, so minute, and intercept the view of each other to that 

 degree, that only a very small section can convey their figure and arrange- 

 ment under the microscope. 



All have a slight incurvature towards the slender stem : their extre- 

 mities terminate in prolongations like thorns. 



This is not a cluster or social zoophyte, however : for numerous single, 

 long, ovate, transparent cells, stand in a row on one side of the subordi- 

 nate parts. As the higher are of smaller size than the rest, probably they 

 come to maturity successively, like some of the preceding. Sometimes 

 there are eight or ten in a row. 



The cell is occupied by an ascidian hydra, with eight long transpa- 

 rent, ciliated tentacula, alike quick and lively in its motion with others of 

 its race. But it is extremely timid and reluctant to shew itself The 

 shape of the cell alters much by its retreat, becoming somewhat irregular, 

 and smaller towards the orifice. It is rarely to be obtained alive. Per- 



