240 ZOOPHYTES. 



guarded by five iiicurving spines of extraordinary length, originating from 

 its upper margin. — Figs. 4, 5. So great a profusion of long, slender, 

 delicate needles, combined with their peculiar form and position, impart 

 a soft and silky aspect to the whole product, which, to the eye, resembles 

 the minutest fern. 



The length of the spines equals six, ten, or even twelve times the 

 diameter of the orifice of the cell. They are longest and more multiplied 

 towards the extremity of the branches, where their accumulation and 

 crossing intercepts a distinct view of the adjacent parts. Those below are 

 commonly impaired ; and the length and number of those above are fre- 

 quently irregular, either from natural or accidental causes. However, the 

 true complement of each cell may be rated at five. 



An ascidian hydra of corresponding nature with the others described 

 in this chapter inhabits the cell. It is colourless, or of the faintest grey, 

 provided with from 12 to 14 rather flattened, slightly recurved, ciliated, and 

 percussive tentacula. But the animal is so vivacious and so restless, as to 

 render inspection by the microscope very inconvenient, and it altogether 

 disturbs that stillness which is essential for the study of the artist. There- 

 fore to obtain complete and perfect delineation of all the parts is imprac- 

 ticable ; interception, and motion combined with their multiplicity, are per- 

 petual obstacles. An opaque reddish or brown ovular substance appears 

 in the body, rising somewhat along with its ascent in the cell. Many 

 vacant cells also contain a dark globular substance at the bottom. Seve- 

 ral authors are disposed to conclude that what is thus seen as a residuum, 

 is the body of the hydra remaining permanently after death. But I have 

 not understood that in either case the nature of the substance is sufficiently 

 ascertained. Hydra;, no doubt, sometimes die in retreat, nevertheless 

 their soft and perishable organs, for the most part, waste away impercep- 

 tibly. 



White corpuscula, very minute, and some of larger dimensions, have 

 been produced in vessels containing specimens of this zoophyte in August 

 and December. They swim actively, and in most respects resemble those 

 described in the next paragraph. One which admitted of closer inspec- 

 tion, proved opaque under the microscope, of soft a]>pearance and variable 



