426 EVENINGS AT THE MICEOSCOPE. 



the ventricose basal part first appear ; the lower barbs 

 flew out before the upper ones, and all were fully ex- 

 panded before tlie attenuated portion began to lengthen. 

 " This, again, is consistent only with the fact of the 

 evolution of the whole. On several occasions of obser- 

 vation on the chambered cnidm of Cyathina Smithii, I 

 have actually seen the nnevolved portion of tlie ectho- 

 rmww, running out through the centre of the evolved 

 ventricose portion. But perhaps the most instructive 

 and convincing example of all was the following. One 

 of the large tangled cnidcB of CBorynactis virdis had 

 shot about half of its wire with rapidity, when a kind 

 of twist, or ' kink,' occurred against the nipple of the 

 cnida, whereby the process was suddenly arrested. 

 The projectile force, however, continuing, caused the 

 impediment to yield, and minute portions of the thread 

 flew out piecemeal, by fits and starts. By turning the 

 stage-screw I brought the extremity of the discharged 

 portion into view, and saw it slowly evolving, a little 

 at a time. Turning back to the cnida, I saw the kink 

 gradually give way, and the whole of the tangled wire 

 quickly flew out through the nipple. I once more 

 moved the stage, following up the ecthorceum, and 

 presently found the true extremity, and a large portion 

 of the wire still inverted ; slowly evolving, indeed, but 

 very distinct throughout its whole course, within the 

 walls of the evolved portion. 



" From all these observations there cannot remain 

 a doubt of the successive eversion of the entire ecthor- 



You ask. What is the nature of the force by which 

 the contained thread is expelled ? " That it is a potent 

 force is obvious to any one who makes the sudden 



