220 The Study of Animal Life part m 



occur, but they become more numerous farther from the land, 

 where the floor of the sea is often covered with a whitish "ooze," 

 most of which consists of Foraminifera which in dying have sunk 

 from the surface to the bottom. They are forming the challc of a 

 possible future, just as many chalk-cliffs and pure limestones repre- 

 sent the ooze of a distant past. In other regions the hard parts 

 of Radiolarians or Diatoms (small plants) or Pteropods (minute mol- 

 luscs) are very abundant. As the Foraminifers have made much 

 of the chalk, so Radiolarians have formed less important siliceous 

 deposits, such as the Barbados Earth, from which Ehrenberg 

 described no fewer than 278 species. At marine depths greater 

 than 2500 fathoms the Globigerina or other Foraminifer shells are 

 no longer present, not because there are none at the surface; but 

 apparently owing to the solution of the shells before they reach 

 such a vast depth. Here the floor is covered with a very fine 

 reddish or brownish deposit, often called "red -clay," a very 

 heterogeneous deposit of meteoric and volcanic dust and of residues 

 of surface-animals. Along with this, in some of the very deepest 

 parts, e.g. of the Central Pacific, there are accumulations of Radio- 

 larian shells, which do not readily dissolve. 1 



9- Relation to other Forms of Life. — On the one hand 

 the Protozoa are devourers of organic debris and the enemies of 

 many small plants ; on the other hand they form the fundamental 

 food of higher animals, helping, for instance, to make that thin sea- 

 soup on which many depend. Moreover, among them there are 

 many parasites both on vegetable and animal hosts. t 



lo. Relation to Man. — in many indirect ways these firstlings 

 affect human hfe, nor are there wanting direct points of contact ; 

 witness a few Protozoa parasites in man, an Amoeba, some Gre- 

 garines, and some Infusorians, which are very trivial, however, in 

 comparison with the numerous plant- parasites — the Bacteria. 



Among the earliest human records of Protozoa is the notice 

 which Herodotus and Strabo take of the large coin-like Nummu- 

 lites, the ' ' Pharaoh's beaifs " of popular fancy. But the minute- 

 ness of most Protozoa kept them out of sight for ages. They were 

 virtually discovered by Leeuwenhoek (b. 1632) about the middle of 

 the seventeenth century, and soon afterwards demonstrated by 

 Hooke to the Royal Society of London, the members of which 

 signed an affidavit that they had really seen them ! In 1755 Rosel 

 von Rosenhof discovered the Amoeba, or "Proteus animalcule;" 

 but his discovery was ineffective till Dujardin in 1835 demonstrated 

 the simplicity of the Foraminifers, and till Von Siebold in 1845 



' For details, see conveniently H. R. Mill's Realm of Nature (Lond. 

 1892). 



