„ 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 .La gen a 



4.Frondicularia 6.Globigerina 



Q.PIanorbulina 



ll.Nummulites 



Fig. 3f>.— Shells of Foraminifera. In 3, /<, and 6, 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 (n. nl\) ; and JO of a form with overlapping whorls ; in 11a half 

 the shell is shown in horizontal section ; b is a vertical section ; <t. aperture of shell ; 1 — 16, 

 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 



