22 ZOOLOGY 



appear, and bhat 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.— 3I0>rEKA Haeckel. 



Beings consisting of transparent protoplasm, containing granvles, some- 

 times forming a net-work, but with no nucleus* or contractile racuole ~ 

 capable of automatically throwing out pseudopodia, and reproducing bif 

 simple sdf-dixision of the body-ma^ into two individuals, or by division 

 into a number of germ-like or spore-like young, which increase in size bjf- 

 absorplion of tlie protoplasm of oUier organisms. 



Group 1. Gymrwmonei-a, comprising the genera Protamceba, Protogenes, 



and Myxodictyum, which do not become encysted. 

 Gi-oup 2. Lepomonera, which become encysted and protected by a- 



case, as in the genera Protomonas, Protomyxa, Vampy- 



rella, and Myxastrum. 



Class II. — Ehizopoda {Root Animalcules). 



General Characters of Ehizopods. — An idea of the form, 

 and internal structure of tins 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 bv 

 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 Bhizopoda, and placed next to 

 Amceba. 



