78 THE OCEAN WORLD. 
It is believed that they are chiefly multiplied by parting with a 
portion of their body substance, which is enabled to take on an 
independent existence, and thus form a new individual. This is 
what naturalists term generation by division—ze, fission. The 
absence of a nutritive and reproductive system in the Ameba, and 
the want of stability in their forms, explain how nearly impossible 
it is to characterise as species the numerous individuals to be met 
with living in fresh or salt water. 
We shall be able to form some idea of the appearance of these 
Fig. 10.—Ameeba princeps (Ehrenberg), Fig. 11.— Various forms of Amoeba diffluens 
magnified roo times. (Muller), magnified. 
beings, rendered mysterious by their very simplicity, by throwing a 
glance upon the two accompanying figures (Figs. ro and 11), bor- 
rowed from the Atlas of Dujardin’s “Les Infusoires,” which we 
shall have occasion to quote more than once. 
We have said that the Amebe change their form every few 
moments under the very eyes of the observer. Fig. 1o represents 
some of the changes of form through which they pass when examined > 
under the microscope. 
Dujardin points out very clearly the identity of structure between 
organisms like Amada and such forms as Diffugia and Arcella. 
All these creatures are without a trace of mouth or true digestive 
