356 EVENINGS AT THE MICROSCOPE. 



recently considering — viz., the Medusae and the Zoo- 

 phytes. They have repeatedly fallen under our observa- 

 tion 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 cnidce or nettling-cells. 



Look at thisbeautiful Scarlet-fringed Anemone (Sagartia 

 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 the blossom-like display is withdrawn: the column closing 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, re- 

 sembling 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 



