24 ZOOLOGY. 
its body. The Amoba reproduces its kind by simple di- 
vision, as seen in Ameba spherococeus Haeckel (Fig. 11). 
This species, unlike others, so far as known, becomes encysted. 
(5), then breaks the cell-wall and becomes free as at A. 
Self-division then begins as at C, the nucleus doubling it- 
self, until at Da and Db we have as the result two individ- 
uals. 
Order 1. Foraminifera.—Besides Ame@ba, several other 
forms, either naked or shelled, produce, by division of an in-. 
ner portion of the body, numbers of ciliated young, as in 
the naked Pelomyza, in certain many-chambered Fora- 
mintfera, and in Collosphe- 
ra. An example may be 
seen in the European Pelo-. 
myxa palustris Greef (Fig. 
12). This creature lives in 
the mud at the bottom of 
fresh-water pools, and when 
first seen resembles little. 
dark balls of mud a milli- 
metre in diameter. Instead 
of one nucleus, there are 
numbers of them, and nu- 
Hip 1 Hpeadete, aca teat contractile vacuoles. 
cortical portion; . diatoms enclosed dn the filled with a fluid, together: 
body-mass. B, ameeba-like bodies originating __ + . 
from the nuclei, which after leaving the body With spicules. The young” 
Breontractle vesicie.—arter Greet? """** are at first amoeba-like (B), 
originating as “shining 
bodies,’? which have resulted from the self-division of the 
nuclei. These ameeba-like bodies finally assume an active, 
monad-like stage C, and move about by means of a cilium. 
or lash. 
We now come to the shelled Ameeba, or genuine Foramt- 
nifera. A common type is Arcella, which secretes a one- 
chambered silicious shell, found in fresh water, and a. 
representative of the monothalamous, or one-chambered, 
Foraminifera* ; while the many-chambered forms are 
marine, of which Globigerina bulloides (Fig. 18), found 
floating on the surface of the ocean, with its psendopodia 
* See Leidy’s Fresh-water Rhizopods of North America, 1879. 
