RHIZOPODA. 135 



based on blocks of lime-stone consisting of Foraminifera, nummidites, 

 or stone coin, and other fossil animalcules. The nummulites vary in 

 size, from that of a most minute object to that of a crown-piece, and 

 many appear like a snake coiled in a round form. A chain of moun- 

 tains in the United States, 300 feet high, seems to be wholly formed 

 of one kind of this fossil-shell. The crystalline marble of the Pyre- 

 nees, and the lime-stone ranges at the head of the Adriatic gulf, are 

 composed of small nummulites. Vast deposits of Foraminifera have 

 ;een traced in Egypt and the Holy Land, on the shores of the Red 

 Sea, Arabia, and Hindostan, and, in fact, may be said to spread over 

 thousands of square miles from the Pyrenees to the Himalayas. 



The fossilised Foraminifera in the Poorbandar lime-stone, although 

 occasionally reaching the twenty-fifth, do not average more than the 

 hundredth part of an inch in diameter ; so that more than a million of 

 them may be computed to exist in a cubic inch of the stone. They 

 may be separated into two divisions those in which the cells are 

 large, the regularity of their arrangement visible, and their bond of 

 union consisting of a single constructed portion between each ; and 

 those in which the cells are minute, not averaging more than the 900th 

 part of an inch in diameter, the regularity of their arrangement not dis- 

 tinctly seen, and their bond of union consisting of many thread-like 

 filaments. To ascertain the mineral composition of the amber-coloured 

 particles or casts, after having found that it was carbonate of lime with 

 which they were surrounded, they were placed for a few moments in 

 the reducing flame of a blow-pipe, and it was observed that on sub- 

 sequently exposing them to the influence of a magnet, they were all 

 attracted by it. Hence, in a rough way, this rock may be said to be 

 composed of carbonate of lime and oxide of iron. 



Truthfully does Lamarck say of the Foraminifera : " Their small- 

 ness renders their bodies contemptible to our eyes; in fact, we can 

 hardly distinguish them ; but we cease to think thus when we consi- 

 der that it is with the smallest objects that nature produces the most 

 imposing and remarkable phenomena. Now, it is here again that we 

 have one of the numerous instances which attest that, in her production 

 of living bodies, all that nature appears to lose on one side in volume, 

 she regains on the other in the number of individuals, which she mul- 

 tiplies to infinity." 



INFUSORIA. 



The class Infusoria, described by Ehrenberg in his work Infu- 

 sionsthierehen, published in 1838, was divided into two great groups, the 



