ADAPTATIONS 149 



and have the habit of encasing themselves in 

 tiny shells, perforated by one or more holes 

 whence their name through which are pro- 

 truded the pseudopodia or protoplasmic pro- 

 cesses by which they take hold of their prey 

 or move about. 



Tiny as they are, their bodies make up vast 

 rocks, for most of the chalk consists of their 

 remains and much of the oolite which forms 

 a great band across England in the district 

 of the Cotswolds is also constructed from the 

 remains of these little creatures. 



Enlarged models of the shells of the Fora- 

 minifera may be seen in most zoological and 

 geological museums and very beautiful objects 

 they are. It is in the selection of the approp- 

 riate kind of substance for the construction of 

 their shells, or " tests " as they are called, 

 that we find our first example of the purposive 

 actions of these little things. 



Carpenter* says on this point : " The tests 

 which they construct, when highly magnified, 

 bear comparison with the most skilful masonry 

 of man. From the same sandy bottom one 

 species picks up the coarsest quartz grains, 

 unites them together with a ferruginous cement, 

 and thus constructs a flask-shaped test, having 

 a short neck and a single large orifice ; another 



* Art. " Foraminifera," Encyclopaedia Britannica. 



