360 EVENINGS AT THE MICROSCOPE. 



but with the state of the muscular contraction of the 

 integument, as, also, I think, with the pleasure of the 

 animal. In a small specimen of S. dianthus, I found the 

 width of a cinclis, measured transversely, ^^h of an inch ; 

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

 twice as great, viz., j-g-yth 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 8. nivea under the 

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

 expand till it was almost circular in outline, and -g^th of 

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

 in an instant it enlarged the aperture to ^-^th 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 ^th of an inch in 

 transverse diameter — a large size ; and I measured one 

 which was even -^g-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 the 

 passage is not absolutely open, at least in ordinary ; but 

 that an exceedingly thin film lies across it. By delicate 

 focussing, I have detected repeatedly, in different degrees 

 of expansion, and even at the widest, the granulations of a 

 membrane of extreme tenuity, and one or two scattered 

 cnidm, across the bright interval. On another occasion, in 

 the case of a cinclis at the edge of the parapet, a position 

 singularly favourable for observation, I saw that this subtle 

 film was gradually pushed out until it assumed the form of 



