II 



PHYLUM PROTOZOA 



53 



increase in the number of chambers there is a multiplication of 

 the nucleus (Fig. 35, 4, b, nu). 



Not only does the shell increase in size by the formation of new 



I.Saccommina 



2.Lagena 



7. Discorbina 



5< Spiroloculma 



3.Nodosaria 



4.Frondicularia G.CIobigerina 



s.sk. 



9.Planorbulina 



ll.Nummtrlires 



FIG. 30. Shells of Foraminifera. In 3, It, and 5, a shows the surface view, and b a section ; 

 8a is a diagram of a coiled cell without supplemental skeleton ; Sb of a similar form 

 with supplemental skeleton (s. sk.); and 10 of a form with overlapping whorls ; in lla half 

 the shell is shown in horizontal section ; b is a vertical section ; a. aperture of shell ; 1 15, 

 successive chambers, 1 being always the oldest or initial chamber. (After Carpenter, Brady, 

 and Butschli.) 



chambers : individual chambers become larger. In this process 

 Jayers of calcareous matter are added to the shell from without by 

 the agency of a thin layer of protoplasm that extends over the 



