356 EVENINGS AT THE MICROSCOPE. 



ing viz., the Medusae and the Zoophytes. They have 

 repeatedly fallen under our observation in examining the 

 specimens of these creatures which we had selected, but I 

 had reserved the fuller elucidation of them for an occasion 

 in which they should come before us under circumstances 

 of such unusual development as greatly to facilitate our 

 researches. The weapons I speak of are the cnida or 

 nettling-cells. 



Look at this beautiful Scarlet-fringed Anemone (Sagarta 

 miniata), expanding to the utmost its disk and tentacles in 

 the clear water of the tank. I touch its body ; instantly 

 the blossom-like display is withdrawn : the column closing 

 over it in the form of a hemispherical button, which goes 

 on contracting spasmodically. At the same time see these 

 white threads which shoot out from various points of the 

 surface ; new ones appearing at every fresh contraction, 

 and streaming out to a length of several inches, resem- 

 bling in appearance fine sewing cotton, twisted and tangled 

 irregularly. 



Now the animal has attained its utmost contraction, and 

 the threads lengthen no more. But already they are 

 disappearing; each is returning into the body by the 

 orifice at which it issued. It is, as you may see by exa- 

 mining it carefully with a lens, gradually contracting into 

 small irregular coils, at that end which is attached to the 

 animal ; and these little coils are, one after the other, 

 sucked-in, as it were, through an imperceptible orifice. 



Before the whole have disappeared, we will secure a 

 portion for examination. For this purpose I cut off with 

 sharp scissors about one- sixth of an inch of the extremity 

 of one of the threads, which now I transfer to a drop 

 of sea-water in the compressorium. These threads are 

 called acontia. 



Examining this fragment under a low power of the 

 microscope, we readily see that, though at first it seems 

 a solid cylinder, it is really a flat narrow ribbon with the 



