OF MICROSCOPIC OBJECTS. 73 



slide and allowed to dry naturally, wben their characters 

 will be very well shown. To obtain anything like a natural 

 appearance, they must be put up in fluid as in Chapter V. 



Next to the Diatomaceae, no class of microscopic objects 

 has been more looked into of late than the Foraminit'era. 

 These animals are almost all marine, having a jelly-like body 

 enclosed in one or more chambers of shell, which is generally 

 composed of carbonate of lime. The shells are made with 

 minute orifices, through which the pseudopodia (false feet) 

 are extended by which the animal is enabled to lay hold of 

 anything to draw itself along. From the possession of these 

 orifices they derive their name, as foramen means a door or 

 opening. They have been found in every depth of sea 

 hitherto sounded, each depth being abundant in certain 

 species; the lowest beds containing the greatest number of 

 specimens, though with less variation of kinds. In chalk 

 they are found in a fossil state, and may readily be shown 

 (see Chapter IV.) ; in limestone and other hard stones they 

 are abundant, and some mountains are composed principally 

 of these shells. 



The methods of obtaining Foraminifera are various. Many 

 may be found upon seaweeds, which should always be ex- 

 amined as soon as possible after gathering. They are found 

 in masses upon some coasts where the waves have carried 

 and left them ; but they are to be found the most abundantly 

 in sand or mud dredged from the bottom of the sea. They 

 must, however, be cleaned and separated from the mass of 

 impurity with which they are usually mixed. This may be 

 done in various ways, according to the nature of the accom- 

 panying matter. If sand alone, as is frequently the case, 

 the whole mass must be thoroughly dried, and then stirred 

 up in clean water. The sand will soon subside by its own 

 weight, but the chambers of the Foraminifera, being Blled 

 with air, will float upon the surface, and may be skimmed 

 off. There is, however, one objection to this mode of pro- 

 ceeding some of these objects are so minute, the chambers 

 containing comparatively so small a quantity of air, that 



