ADAPTATIONS 93 



Enlarged models of the shells of the foramini- 

 fera may be seen in most zoological and geological 

 museums and very beautiful objects they are. It 

 is in the selection of the appropriate kind of sub- 

 stance 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 1 says on this point : " The tests which 

 they construct, when highly magnified, bear com- 

 parison 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 picks up the finer grains 

 and puts them together with the same cement into 

 perfectly spherical tests of the most extraordinary 

 finish, perforated with numerous small pores dis- 

 posed at pretty regular intervals. Another species 

 selects the minutest sand-grains and the terminal 

 portions of sponge-spicules, and works them up 

 together apparently with no cement at all, but 

 by the mere laying of the spicules into perfect 

 white spheres like homoeopathic globules, each 

 showing a single-fissured orifice. And another 

 which makes a straight, many-chambered test, the 

 1 Art. " Foraminifera," Encyclopedia Britannica. 



