SEA-ANEMONES: THEIR WEAPONS 405 



the lids may separate in various degrees, until they are 

 retracted to the margin of the oval pit, and the whole 

 orifice is open. 



"The dimensions of the cinclides vary not only with the 

 species, and probably also with the size of the individual, 

 but with the state of the muscular contraction of the in- 

 tegument, as, also, I think, with the pleasure of the ani- 

 mal. In a small specimen of S. dianihus, I found the 

 width of a cinclis, measured transversely, itath of an inch; 

 but that of another, in the same animal, was more than 

 twice as great; viz., mth of an inch. This was on the 

 thickened marginal ring, or parapet, which in this species 

 surrounds the tentacles, where the cinclides are larger than 

 elsewhere. Watching a specimen of S. nivea under the 

 microscope, I saw a cinclis begin to open, and gradually 

 expand till it was almost circular in outline, and ^hrth of 

 an inch in diameter. I slightly touched the animal, and 

 it in an instant enlarged the aperture to irtath of an inch. 

 In a specimen of S. bellis, less than half-grown, I found 

 the cinclides numerous, and sufficiently easy of detection, 

 but rather less defined than in dianthus or nivea. They 

 occurred at about every fourth intersept, three intersepts 

 being blind for each perforate one, and about three or four 

 in linear series, but not quite regularly in either of these 

 respects. In this case they were about sVth of an inch in 

 transverse diameter a large size; and I measured one 

 which was even i&th of an inch. By bringing the animal 

 before the window, I could discern the light through the 

 tiny orifices with my naked eye. 



"From several good observations, and especially from 

 one on a cinclis, widely opened, that happened to be close 

 to the edge of the parapet of a dianthus^ I perceived that 



