GEOLOGICAL IMPORTANCE OF THE FORAMINIFERA. 11 



broken up, it was found to contain only trifling remains of a finely 

 granular organic substance, which, after careful and continued observa- 

 tion, exhibited no trace of motion such as is often, under other circum- 

 stances, presented in separated particles of the animal substance, nor 

 could he perceive any vestige of a young one in process of development. 

 The almost complete absence of any organic contents in the shell of an 

 individual which from eight to fourteen days previously was creeping 

 about, renders it probable that the whole (or, at any rate, part) of its body 

 had been transformed into young ones. 



(25.) It is astounding to reflect upon the multitudes of these micro- 

 scopic shells which crowd almost every sea-beach. In some cases at 

 least one-half of the bulk of the sand seems to consist of these elegant 

 organisms. Plancus (Ariminensis, De Conchis minus notis) counted 

 6000 in a single ounce of sand from the shores of the Adriatic ; and 

 D'Orbigny estimated that an ounce of sand procured from the Antilles 

 contained not fewer than 3,800,000 ! The numbers therefore contained 

 in a square yard are beyond all human calculation ; and yet, what is 

 that when compared with the extent of sea- coast in all parts of the 

 globe ? Probably therefore no race of animals is more numerically im- 

 portant than that we are now considering. Their remains constitute a 

 great proportion of the so-called sand-banks which often so materially 

 interfere with navigation by obstructing the entrance to bays and 

 straits, or, as is the case with the port of Alexandria, blocking up 

 harbours. They enter largely into the formation of coral islands, and 

 not unfrequently compose extensive geological deposits. One solitary 

 species of the genus Fusulina has, in Kussia, given rise to enormous 

 beds of calcareous shells. The cretaceous formations both of France 

 and England contain them in immense quantities. The tertiary strata 

 abound with numerous species; and the very stones of which the 

 largest of the Pyramids of Egypt is built are principally composed of 

 shells (Nummulites) belonging to this important group. The tertiary 

 basins of the Gironde, of Austria and of Italy, and more especially 

 the " calcaires grossiers " of the vast Parisian basin, are in some parts 

 so filled with them, that 58,000 have been counted in a cubic inch, or 

 about 3,000,000,000 in a cubic yard figures that may well spare us 

 further calculation. In fact, it might be stated without exaggeration, 

 that the city of Paris, as well as many of the towns and villages in the 

 surrounding departments, are almost entirely built of stones that seem 

 to be mere agglomerations of these microscopic shells. 



(26.) The substance of the shell in the Foraminifera varies to a 

 certain extent in accordance with its mode of growth. When the 

 calcareous investment is made up of segments involving each other, 

 it is of a dense texture, resembling porcelain. When the segments 

 alternate without a spire, or when the spiral revolution is oblique, the 

 shell is porous, and perforated, more especially in the last-formed com- 



