362 EVENINGS AT THE MICROSCOPE. 



more, or all, of these organs hang down in the water 

 motionless, lengthening more and more, especially 

 when the bell is still, until they reach a length some 

 twelve or fifteen times that of the bell, or ximbrella. 

 Then suddenly one will be contracted, and, as it were, 

 shrivelled, to mere fragments of a quarter of an inch 

 long ; then lengthened again to an inch or two ; then 

 shortened again. I^ow the little bell resumes its ener- 

 getic pumping, and shoots round and round in an 

 oblique direction, the summit always going foremost, 

 and the tentacles streaming behind in long trailing 

 lines. Now it is again arrested; the bell turns over 

 on one side and remains motionless, and the tentacles, 

 as " fine as silkworms' threads," float loosely in the 

 water, become mutually inter-tangled, instantly free 

 themselves, pucker and shrivel up, slowly lengthen, 

 and hang motionless again, or, as the bell allows itself 

 to sink slowly, are thrown into the most elegant curves 

 and arches. 



Though these tentacles look at first like simple 

 threads of extreme tenuity, yet when viewed closely 

 they are seen to be composed of a succession of minute 

 knobs separated by intervals — like white beads strung 

 on a thread ; the beads being more remote from each 

 other in proportion as the tentacle is lengthened. 



This structure is worthy of a more minute inves- 

 tigation. We will, therefore, confine our little Sarsia 

 in this narrow glass trough, which is sufficiently deep 

 to allow its whole form to be immersed, though some- 

 what flattened; which is an advantage, as its move- 

 ments are thereby impeded. Now, with a power of 

 300 diameters you see that each of the knobs of the 

 tentacle is a thickening or swelling of the common 



