ACTINLGi AND OTHER ACTINOID POLYPS. oD 
700 diameters. Figure 1 represents one of the lasso-cells of 
the Actinia, Corynactis viridis, with its lasso coiled up within, 
its actual length is about a 350th of an inch. Figure 2 is the 
same with the lasso out, though less than half of the long 
thread is shown. Figure 3 is the lasso-cell of the polyps of a 
European coral, the Caryophyllia Smithii. Jt differs from 
figure | in having the basal part of the lasso within the cell or 
sheath strait and stout; it is this part which makes the first 
portion of the extended lasso. <A view of part of the latter is 
represented in figure 4, and of the extremity of the same in 
figure 5. The lasso-cells in the above species are from a 240th 
to a 360th of an inch in length. In the Metridium margina- 
tum, an American Actinia occurring along the coast of the Uni- 
ted States, north of New York, the length of one of the lasso- 
cells, according to Dr. Leidy, was about a 400th of an inch, 
and the character of the extended lasso was much like that of 
figure 4. The lower part of the lasso, for a length 14 times 
or more longer than the cell or sheath, is usually thickened, 
and sometimes slenderly spindle-shaped, while the rest is an 
_ even slender thread; and the thickened part and sometimes 
all the rest, as above shown, is spirally wound by a slender 
line, sometimes elevated, set with short hairs or bristles. The 
thread-like portion nay be wanting or very short. The lasso 
is often twenty times as long as the cell or sheath, and occa- 
sionally forty times; but if the thread-like part is absent, only 
one and a half to two times. 
A lasso-cell once used is afterward worthless; for the tube 
cannot be returned to the sheath. But those thus expended 
are not missed, as the polyp has indefinite supplies of such 
weapons, and also ready means of refurnishing itself. 
Figures 6, 7, 8, 9, 10, on the preceding page, illustrate 
different stages in the development of a lasso-cell (fig. 10) 
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