V] 



OF FLUTED OR PLEATED CELLS 



421 



tends to fold or wrinkle, longitudinally in its wider part and trans- 

 versely or annularly in its narrow neck, is thus completely explained. 

 An identical phenomenon is apt to occur in the little flask-shaped 

 gonangia, or reproductive capsules, of some of the hydroid zoophytes. 

 In the annexed drawings of these gonangia in two species of Cam- 

 panularia, we see that in one case the httle vesicle 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. In the other Campanularian the 

 vesicles are long, narrow and tubular, and here a transverse folding 



Fig. 134. Nodosaria scalaria 

 Batsch. 



135. Gonangia of Canjpanularians. 

 (a) C. gracilis; [b) C. grandis. 

 After AUman. 



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. 



An everted rim, or short neck, may arise in various ways apart 

 from the phenomenon of the hanging drop. To make a "thistle- 

 head" the glassblower blows a bubble, and from that another one; 

 after blowing the latter up large and thin he crushes it to pieces, 

 and melting down what is left of it he forms the rim. I take it that 

 the neck or rim of the shell in Diffiugia is formed in an analogous 

 way, in connection with the growth of a new individual at the mouth 



