22 ZOOLOGY 



appear, and that from forms resembling them all other organ- 

 isms have originated. We can conceive at least of no simpler 

 ancestral form; and if organized beings were originally pro- 

 duced from the chemical elements which form protoplasm, 

 one would be naturally led to suppose that the earliest form 

 was like Protamceba. It would follow from this fact that the 

 Monera are as low as any plants, and that animals appeared 

 contemporaneously with plants. 



Having studied a few typical forms of Monera, we are 

 prepared to briefly define the group and tabulate the sub- 

 divisions of the class. 



CLASS I. MONERA HAECKEL. 



Beings consisting of transparent protoplasm, containing granules, some- 

 times forming a net-work, but with no nucleus* or contractile vacuole ; 

 capable of automatically throwing out pseudopodia, and reproducing by 

 simple self-division of the body-mass into two individuals, or by division 

 into a number of germ-like or spore-like young, wliicli increase in size by 

 absorption of the protoplasm of other organisms. 



Group 1 . Gymnomonera, comprising the genera Protamceba, Protogenes, 



and Myxodictyum, which do not become encysted. 

 Group 2. Lepomonera, which become encysted and protected by a 



case, as in the genera Protornonas, Protomyxa, Vanipy- 



rella, and Myxastrum. 



CLASS II. EHIZOPODA (Root Animalcules}. 



General Characters of Rhizopods. An idea of the form 

 and internal structure of this group can be obtained by a 

 study of Amoeba, which may be found sliding over the sur- 

 face of the leaves of plants growing in pools or ponds of 

 fresh water. Our common Amoeba has been studied by 

 H. J. Clark. Fig. 10 represents this animal in the three 

 more usual forms which it assumes. From time to time 

 the sides of its body project either in the form of simple 

 bulgings, or suddenly it throws out foot-like projections 



* Should a nucleus be found hereafter to occur in the Monera, the 

 group should be merged into the Rhizopoda, and placed next to 



Amoeba. 



