RHIZOPODA—FORAMINIFERA. 79 
cavity, but although they have neither mouth nor stomach, yet, 
according to Professor Kolliker, and as has been mentioned 
before, they take in solid nutriment, and reject what is indigestible. 
When in its progress through the water one of these minute organisms 
approaches one of the equally minute Algz, from which it draws 
nourishment, it seizes the plant with its pseudopods, and gradually 
encloses it on all sides; the pseudopods, to all appearance, be- 
coming more or less shortened in the process. In this way the 
captive is brought close to the surface of the body; a cavity is 
apparently then formed, in which the prey is lodged, which closes 
round it on all sides. In this situation it is gradually drawn towards 
the centre, and passes at last entirely into the mass, when the 
engulfed morsel is gradually dissolved and digested. 
RETICULOSA, OR FORAMINIFERA. 
What, then, is a Foraminifer? It is a very small calcareous shell 
nearly invisible to the naked eye; for, in general, its dimensions 
range between ‘oo5 to ‘oso of an inch in length. Examine under a 
microscope the sand of the ocean, and it will be found that one-half of 
it consists of the débris of minute shells, of various but well-defined 
forms, each pierced with a number of holes. To this they are 
indebted for their name Foraminifera, from foramen, a hole. With 
these microscopic animals Nature has worked wonders in geological 
times ; nor have the wonders ceased in our days. 
The sand of the littoral zone of all existing seas is so full of these 
minute but elegant shells, that it is often nearly one half composed 
of them. Ehrenberg, the celebrated German microscopist, was 
recently invited by the Prussian Government to assist in tracing the 
robbery of a special case of wine. It had been re-packed in littoral 
sand only found in an ancient sea-board in Germany. The criminal 
was thus detected. M. d’Orbigny found in three grammes (forty- 
six grains troy) of sand from the Antilles, 440,000 shells of Fora- 
minifera. Bianchi found in thirty grammes (467 grains) from the 
Adriatic, 6,000 of these shells. If we calculate from these facts 
the proportion of these beings contained in a cubic metre alone of 
sea-sand, we reach a figure which passes all conception. What would 
this be if we could extend the calculation to the immensity of surface 
covered by the waves which surround the globe? | — 
M. d’Orbigny has satisfied himself, by microscopic examination of 
sands from all parts of the globe, that it is the débris of Foraminifera 
along with the sea-sand, which form, in all existing seas, those 
