18 ANIMAL LIFE 



one outside of the capsule. In the protoplasm inside of 

 the capsule lies the nucleus or nuclei ; and from the proto- 

 plasm outside of the capsule rise the numerous fine, thread- 

 like pseudopods which project through the apertures in the 

 shell, and enable the animal to swim and to get food. 



Most of the myriads of the simplest animals which 

 swarm in the surface waters of the ocean belong to a few 

 kinds of these shell-bearing Globigerinae and Radiolaria. 

 Large areas of the bottom of the Atlantic Ocean are cov- 

 ered with a slimy gray mud, often of great thickness, which 

 is called globigerina-ooze, because it is made up chiefly of 

 the microscopic shells of Globigerinae. As death comes to 

 the minute protoplasmic animals their hard shells sink 

 slowly to the bottom, and accumulate in such vast quanti- 

 ties as to form a thick layer on the ocean floor. Nor is it 

 only in present times and in the oceans we know that the 

 Globigerinae have flourished. All over the world there are 

 thick rock strata which are composed chiefly of the fos- 

 silized shells of these simplest animals. Where the strata 

 are made up exclusively of these shells the rock is chalk. 

 Thus are composed the great chalk cliffs of Kent, which 

 gave to England the early name of Albion, and the chalk 

 beds of France and Spain and Greece. The existence of 

 these chalk strata means that where now is land, in earlier 

 geologic times were oceans, and that in the oceans Globi- 

 gerinse lived in countless numbers. Dying, their shells 

 accumulated to form thick layers on the sea bottom. In 

 later geologic ages this sea bottom has been uplifted and 

 is now land, far perhaps from any ocean. The chalk strata 

 of the plains of the United States, like those in Kansas, are 

 more than a thousand miles from the sea, and yet they are 

 mainly composed of the fossilized shells of marine Pro- 

 tozoa. Indeed, we are acquainted with more than twice as 

 many fossil species of Globigerinae as species living at the 

 present time. The ancestors of these Globigerinae, from 

 which the present Globigerinae differ but little, can be 



