18 zooLoar. 



duetive nucleus, and several contractile vesicles, rudejy an- 

 ticipating the heart of higher animals. Protozoans repro- 

 duce by self-division and the formation of motile germs 

 (zoospores), and in the Infusoria of ciliated young. There 

 is thus a great range of forms leading from the most primi- 

 tive type (Protamwba) to the most specialized forms, such 

 as the bell animalcule {Vorticella.) 



Class I. — Monera [Moners). 



General Characters of Moners. — This group comprises 

 the simplest forms of Protozoans, whence the name Monera 

 (/Aovi^fjsi, simple). The lowest forms are almost identical 

 in appearance with the lowest plants, and they can only 



Fig. 8. — Proiomonas amyli, greatly magnified. A, when encysted; x, germs or zo- 

 ospores ; y, food-mass. B, germ freed from the parent-cyst. C, D, older germs. S, 

 adult encysted ;j^, food ; e, projection inward of the cell-wall ; x, wall of the cyst ; t, 

 germs. — After Cienkowski. 



be claimed to be animals from their resemblance to higher 

 forms leading to Amoeba, which, in turn, is connected by a 

 series of forms leading to undoubted animals, such as the 

 shelled Rhizopods (Pig. 14). 



The Monera differ from the Rhizopods {Amoeba, etc.) in 

 wanting a nucleus and contractile vesicles. Their body- 

 substance is homogeneous throughout, not divided into a 

 tenacious outer and softer inner mass, as in Amoeba. They 

 move by the contraction of the body, and the irregular pro- 

 trusion of portions of the body forming either simple pro- 

 cesses (pseudopodia) or a network of gelatinous threads. 

 The food, as some diatom, desmid, or protozoan, is swallowed 



