XII] 



OF THE FORAMINIFERA 



603 



the coiled tubes which httle worms such as Serpula and Spirorbis 

 make^ under similar conditions) the spiral disc is itself asymmetrical, 

 its whorls being markedly flattened on their attached surfaces. 



Fiff. 31G. Discorhitia bertheloti, d'Orb. 



We may also conceive, among other conditions, the very 

 curious case in which the protoplasm may entirely overspread the 

 surface of the shell without reaching a position of equihbrium; 

 in which case a new shell will be formed enclosing the old one, 



