82 
THE OCEAN WORLD. 
creatures the presence of a necessity gives the power to create fl® 
organ by the mere will of the creature, while man, with all h' s 
genius, cannot manufacture a hair. To the present clay, however, ' ve 
have not been able to discover any organ of nutrition in the For®' 
minifera ; they have no stomach, properly so called, but Nature b® 5 
gifted them with a peculiar tissue, at once gelatinous and contractile 
and essentially simulative, which probably serves the same purpose. 
We have already said that the shells of these minute zoophytes vary 
much in form. They are generally many-chambered, each chamber 
communicating by pores in the walls ; the different gelatinous part 5 
of the animalcules are, in this manner, placed in continual commur®' 
cation with each other. Alcide d’Orbigny, to whom we owe almost 
all that is known of the class, has distributed them into six family 
making the form of the shell the basis of their arrangement. The?® 
six families include sixty genera, and more than sixteen hundred 
species, the families being as follows : — • 
I. Monostega. — Animals consisting of a single segment. Shell of 
a single chamber. 
Fig. 12. Orbuliiia uulversa. 
II. Stichostega. — Animal in segments, arranged in a single li» e ' 
Fig. 13. Dentalina communis. 
Shell in chambers, superimposed linearly on a straight or curved » slS ' 
