THE CONSERVATION OB' LIFE 



219 



and Pyrenees, deposits of the familiar nummulites. These are 

 probably the largest unicellular organisms which ever lived, for 

 we know shells of the size of a florin. 



But let us return to our subject : it is not the protozoans 

 as such but the natural phenomena of reproduction which are 

 of interest to us here. Some Foraminifera, with a compara- 

 tively soft shell, are, like Amoebae, able to reproduce by a simple 

 drawing-out process (constriction), whereupon each of the 

 daughter-animalcules completes the inherited shell-half by 

 regeneration. Others leave 

 their house when the time of 

 reproduction comes and 

 divide, whereupon each half 

 builds for itself a new house. 

 Other species exhibit more 

 remarkable deviations. Let 

 us examine these in the little 

 Euglypha alveolata which 

 lives in fresh water. This 

 pretty animalcule possesses a 

 shell shaped like a pear or 

 egg, artistically built of 

 minute silica-plates. At the 

 pointed end is a round open- 

 ing through which Euglypha 

 protudes its protoplasmic 

 pseudopodia and takes in 

 food. When it is about to 

 divide it secretes first of all 

 proximity of the nucleus, 



FIG. 52. NUMMULITES. 



in the cell-body, in immediate 

 numerous minute silica-plates. 

 Then all pseudopodia are retracted, and in their place appears 

 a thick, round lump of protoplasm, representing about half 

 of the entire body substance. Now the nucleus begins to 

 change : in a highly complicated manner it divides into two 

 parts which are exactly alike. While one half remains in the 

 shell the other wanders into the protruded protoplasm. In the 

 meantime the silica-plates have also passed on to the protruded 

 protoplasm and formed themselves into a connected shell which 

 is an exact replica of the old house. A chitinous glue joins the 



