xiv COMPLEXITY OF SHELL 151 



The new chambers may be added in a straight line (Fig. 

 31, A) or in a gentle curve, or in a flat spiral (Fig. 31, B), 

 .or like the segments of a Nautilus shell, or more or less 

 irregularly. In this way shells of great variety and beauty 



FIG. 32. Section of one of the more complicated Foraminifera 

 (Aveolina), showing the numerous chambers containing protoplasm 

 (dotted), separated by partitions of the shell (white). x 60. (From 

 Gegenbaur after Carpenter. ) 



of form are produced, often resembling the shells of Mol 

 lusca, and sometimes attaining a marvellous degree of com- 

 plexity (Fig. 32). The student should make a point of 

 examining mounted slides of some of the principal genera 

 and of consulting the plates in Carpenter's Introduction to 

 the Study of Foraminifera (Ray Society, 1862), or in Brady's 

 Report on the Foraminifera of the " Challenger" Expedition, 

 in order to get some notion of the great amount of dif- 

 ferentiation attained by the shells of these extremely simple 

 organisms. 



