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 



2.Lagenct 



4.Frondicularia e.Clobigerina 



Q.PIanorbulina 



ll.Nummtriires 



FIG. 30. Shells of Foraminifera. In 3, 4, and 5, a shows the surface view, and b a section ; 

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

 with supplemental skeleton (*. #!-.) ; 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 

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

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



