32 THE FOEAMINIFERA 



CHAPTER IV 



THE SHELL STRUCTURE OF THE FORAMINIFEEA AND 

 THEIR PLANS OF GROWTH 



It is due to the fact that the Foraminifera present 

 such an extensive variety of regular and beautiful 

 forms that their shells are so much in favour with 

 beginners in microscopy. 



Fig. 18. 



a, Test of Cristellaria crepidula (F. and M.) ; h, siliceous internal cast of the 

 same species from 'flint-meal,' Upper Chalk. Highly .magnified. After Eleij. 



The plan of the shell is dependent upon the 

 arrangement of the continuously budded segments, 

 and this is partially determined by the form of 

 the primordial or initial chamber. It may be that of 

 a straight series of segments, gradually increasing 



