382 THE INHABITANTS OF THE SEA. 



multitudes, thus have they swarmed in the waters of the pri- 

 meval seas from the first dawn of creation, and piled up the 

 monuments of their existence in vast strata of limestone. A 

 great part of the rocky belt from Eiigen to the Danish isles, 

 the white chalk" cliffs which, beginning in England, extend 

 through France as far as Southern Spain, are chiefly com- 

 posed of the shells of Foraminifera, and the zone of Nummu- 

 lite limestone, which served to build the huge quadrilateral 

 monument of Cheops, forms a band, often 1,800 miles in 

 breadth, and frequently of enormous thickness, from the 

 Atlantic shores of Europe and Africa through Western Asia 

 up to North India and China; enough to satisfy the most 

 extravagant architectural folly of millions of despots. So 

 important is the part which these beings, individually so 

 minute, have performed and still perform in the geological 

 annals of the globe. 



Many of these "minims of nature" consist of only one 

 chamber, and hence are called unilocular or monothalamous ; 

 but a vast proportion consist of several chambers, and hence are 

 called multilocular or polythalamous. The latter, however 

 numerous their chambers or seemingly complex their structure, 

 always originate as a single shell. The primitive jelly-sphere, 

 or first sarcode segment, secretes around itself its appropriate 

 calcareous envelope. Having grown too large for its habitation, 

 it protrudes a portion of itself without, and thus forms a second 

 segment. If by a process of spontaneous fission this segment 

 becomes quite detached from its parent, and repeats the life 

 and method of reproduction of the latter, a series of mono- 

 thalamous shells will be formed. But if by means of a sar- 

 code band the primitive segment maintains its connection with 

 its immediate offspring, and this, repeating the reproductive 

 process, does the same, a compound shell will, of course, be the 

 result. 



Among the microscopic denizens of the ocean, the Poly- 

 cystina rival the Foraminifera both by their number and their 

 wonderful elegance of form and structure. Their body consists 

 of the same viscid homogeneous plastic mass, termed " sarcode" 

 by the naturalists ; like them they are capable of protruding it 

 through the foramina with which their shell is pierced, and 

 consequently they are ranked with them among the Rhizopods, 



