Ji6 



PROTOZOA. 



-Shells of Foraminifera. 

 Ay Nummulitea. 



B, Nonionina. 



C, Lagena. 



X>, Globigerina. 

 E, Milliola. 



such forms were long considered to be minute Molluscs. The shells of th 



Globigerina, or globe- bearers (D), help largely to build up Chalk. They are sai 



to constitute almost one-third of the ooz 

 covering vast areas of the sea-bottom i 

 the North Atlantic. Milliolite shells (E 

 are the chief constituent of the stone c 

 which the houses of Paris are built 

 Nummilitic limestones cover an enormou 

 area of Central and Southern Europe 

 North Africa, West Asia, and India. Al 

 limestones indeed abound in the shells o 

 Foraminifera, some species being foun( 

 in the Coal formations also. 



The Foraminifera nearly all live in th 

 sea, creeping along its bottom ; but som 

 float about. Young ones are produced b, 

 the breaking up of the protoplasm int^ 

 small portions, which secrete their charac 

 teristic shelly covering before leaving th 

 body of the parent. Some young Fora 



miuifera have very simple single shells, but others are provided from the firs 



with a three-chambered shell. 



Passing from those Protozoa whose protoplasmic processes are mer 



protrusions of the soft body showing no definite shape, but constantly 



varying, we come to others in which these body processes are highl, 



specialised, and here again we have naked and shelled forms. 



The Heliozoa, or Sun animalcules (Fig. 4), have straight, ray-lik 



pseudopodia, which, however, are not rigid, but when brought in contac 

 with particles of food. 

 The Heliozoa. can contract or bend so -. i . 



as to draw them in to- ■. '.. • . ; . .•' .■' 



wards the body. Sometimes a minute •."■'"•.'.':.'/.■.•■ ./ . . 



animalcule, touching one of the rays, appears 



to become paralysed and to glide down the 



pseudopodium to its root, where a protruding 



part of the protoplasm can draw in it. In 



most of the Heliozoa the body is naked, and 



the contractile vesicle is very conspicuous, 



often growing to a very large size at the 



edge of the body, and bursting with such 



violence as to shake the whole animal. 



Some idea of the size of these animalcules 



Cin be gained from the fact that four hundred 



of them set closely side by side would 



measure an inch. In spite of the formidable rays by which the Sui 



animalcule is surrounded, it often falls a prey to a simple Amceba, whic 



ei(:her envelops the whole animalcule or tears out portions of its soft body. 



Next in order above the Sun animalcules, and far more complicated i 



appearance on account of their elaborate skeletons, ar 



The Eadiolaria. the Ray animalcules or Radiolaria. In these the soi 



body is not, as in the Foraminifera, enclosed in an almos 



continuous outer shell, but the hard matter, usually of a flinty naturt 



Fig. 4, 



■The Scn Animaioulb 

 {Actinophrys sol). 



