V] 



OF THE SIMPLER FORAMINIFERA 



263 



has the flask-shaped or unduloid configuration of a Lagena ; and 

 here the walls of the flask are longitudinally fluted, just after the 

 manner we have witnessed in the latter genus. But in the other 

 Campanularian the vesicles are long, narrow and tubular, and here 

 a transverse folding or pleating takes the place of the longitudinally 

 fluted pattern. And the very form of the folds or pleats is 

 enough to suggest that we are not dealing here with a simple 

 phenomenon of surface-tension, but with a condition in which 

 surface-tension and stiffness are both present, and play their 

 parts in the resultant form. 



Passing from the solitary flask-shaped cell of Lagena, we have, 

 in another series of forms, a constricted cylinder, or succession 



a h c d e f g 



Fig. 89. Various Foraminifera (after Brady), a, Nodosaria simplex; b, N. 

 pygmaea; c, N. costulata; e, N. hispida; f, N. elata; d, Rheophax (Lituola) 

 distans; g, Sagrina virgata. 



of unduloids ; such as are represented in Fig. 89, illustrating 

 certain species of Nodosaria, Rheophax and Sagrina. In some of 

 these cases, and certainly in that of the arenaceous genus Rheophax, 

 we have to do with the ordinary phenomenon of a segmenting or 

 partially segmenting cylinder. But in others, the structure is 

 not developed out of a continuous protoplasmic cylinder, but as 

 we can see by examining the interior of the shell, it has been 

 formed in successive stages, beginning with a simple unduloid 

 "Lagena," about whose neck, after its solidification, another drop 

 of protoplasm accumulated, and in turn assumed the unduloid, 

 or lagenoid, form. The chains of interconnected bubbles which 



