PROTOZOA AND SPONGES 42JL _ 



power of motion ; and we directly discern thrust out from 

 its edge, variable processes, in the form of arms, of clear, 

 perfectly colorless, and most delicate jelly, sometimes 

 pointed, sometimes blunt, which slowly change their form 

 and position. By the aid of these, a feeble and irregular 

 motion is given to the box, which is sometimes turned 

 partly over; when we perceive that its under-side is flat 

 or probably concave, and that its outline is cut into facets. 

 The lorica is somewhat flexible, for the edges at two op- 

 posite points are sometimes bent down toward each other, 

 so as to give the creature the form of a crescent. The 

 internal viscera are dimly discernible through the colored 

 lorica, and resemble those of Amoeba. A dark oval ring 

 is commonly seen at one side, which is probably the out- 

 line of the contractile bladder. It may, in fact, be con- 

 sidered as an Amoeba, whose external surface has the 

 power of secreting a symmetrical shell of horny, or 

 chitinous substance. The lorica is about one five-hun- 

 dredth of an inch in diameter. This species is named 

 Arcella vulgar is. 



Laying aside our live-box with its contents for the 

 present, we will have recourse to the tank of sea- water for 

 one or two other objects of intermediate interest. On the 

 green and brown mossy seaweed which covers the rocks 

 on the bottom you see many white specks clinging to the 

 filaments; and there are several adhering to the sides of 

 the tank. These are little living shelled animals of the 

 class Foraminifera, and these which you see include sev- 

 eral species. By bringing your eye assisted by the lens 

 to bear upon one of these latter, you perceive that it is a 

 little discoid spiral shell, of very elegant form, marked 

 with curved diverging grooves. This is the pretty little 



