392 EVENINGS AT THE MICEOSCOPE. 



come a large circular disk of tlirice the diameter of the 

 body : its substance was gelatinous, full of oblong 

 granules, arranged concentrically. I neither saw this 

 disk evolved nor retracted ; but after some time, on 

 looking at it, the same phenomenon was repeated. In 

 order to obtain a better sight of it, but without sus- 

 picion of what I was about to effect, I slightly turned 

 the tube of the, box, cari'ying with it the alga to which 

 the polype was attached, my eye upon it attentively 

 observing all the time. The base of the polype moved 

 away from its position, but the broad disk was im- 

 movable. I continued to turn the upper glass, until 

 at length the body was dragged out so as to be con- 

 siderably attenuated ; still the disk maintained its hold 

 on the lower glass, with no other change than that 

 of being elongated in the direction in which it was 

 dragged. At length it slowly gave way, and resumed 

 its original shape by gradual and almost imperceptible 

 diminution of the circumference. 



Around this expansile, but now fast-closed mouth, 

 you observe four tentacles, radiating in a plane at 

 right angles to the axis of the thread, towards the four 

 cardinal points; they are long, slender, straight, and 

 each is terminated by a globose head of considerable 

 size, resembling the arms of certain screw-presses, 

 which are loaded with terminal globes of metal to in- 

 crease their impetus when turned. 



The structure of these tentacles is very interesting. 

 The stem contains a core or central chain of large cells, 

 which take a somewhat square outline from mutual 

 pressure. The surface is roughened with small swell- 

 ings, from each of which projects a long and excessively 

 attenuated hair {paVpocil), which is probably a very del- 



