THE SHELL STRUCTUEE 



35 



septal face of a foraminifer, and they constitute 

 the external apertures of each chamber in succes- 



FiG. 'iO.— Mkdiax Sections of Foraminifera, showing Stolon 

 Passages through the Septa. 



A = Peneroplis, with imperforate shell-wall; B = Cristellaria, with perforate 



shell-wall. 



sion as the segmental buds are added to the growing 

 shell. 



The stolon passages are, as may be supposed, 



.' a 



Fig. 21. 



A, Apertures (a) on the septal face of Peneroplis pertnsuis. 

 )!, Single aperture in Anomalina ariminensis. 



more numerous in the imperforate group, which, 

 generally speaking, has a series of apertures, as in 



a 2 



