PHYLUM PROTOZOA 



53 



increase in the number of chambers there is a multiplication of 

 the nucleus (Fig. 34, 4, b, nu). 



The shell presents two leading types of structure, apart from 



2.Lagena 



4.Frondicularia G.CIobigerina 



Q.PIanorbulina 



ll.Nummulil'es 



FIG. 35. Shells of Foraminifera. In 3, k, 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 (s. s&.) ; 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.) 



the form and arrangement of the chambers : either it is of a 

 porcelain-like texture and provided with a single terminal aperture, 

 (Fig. 34, 4), or the texture is glassy and the whole shell perforated 



