LOW LIFE. 



things that are much larger than their mouths ; but there is 

 no occasion to split hairs just now. These Foraminifera are 

 in some cases invisible to the unassisted vision, but as each 

 is pierced with many pores, it follows that the individual pore 

 must be almost inconceivably small, though still smaller are 

 the wisps of jelly that protrude through them and invest the 

 outside of the shell. For it must not be supposed that these 

 structures are secreted like the shell of the snail, that the 

 animal may live within it ; rather it is like our own skeleton, 

 built up within our bodies. 



Some of these shells have but one chamber, like Lagena, 

 which is flask-shaped, and Entosolenia, in which the long neck 

 of the flask has been pushed down inside the globose portion. 

 Others have many compartments, but these are subject to 

 great variety of arrangement, each species having its own 

 special form. Dentalina has the chambers placed one behind 

 the other in a straight or curved line. In Nonionina, Polysto- 

 mella, Rotalina, Globigerina, and others they are rolled in a 

 spiral, and resemble the chambered shell of the Nautilus; or 

 they may be twined, not spirally, round an axis, each making 

 a half-tarn. 



In some respects similar to the Foraminifera are the Polycis- 

 tina, which are equally minute creatures, whose skeletons are 

 of flint instead of chalk, and the perforations 

 are so large and so close together that the 

 term pore no longer adequately expresses 

 their proportionate size. They are more like 

 windows, but with little intervening stone- 

 work. The jelly-substance, called sarcode, 

 flows out through all these windows in the 

 form of threads (called pseudopodia or false 

 feet) as in the Foraminifera, spreading over 

 the outer surface and acting as legs and arms 

 by means of which the creature moves and 

 captures its food. They feed upon infusoria 

 of various kinds, and the diatoms and desrnids, 



POLYCISTIN. 



