18 ZOOLOGY. 



ductive nucleus, and several contractile vesicles, rudely 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 (Protamceba) 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 

 (/^ovjy/js?, simple). The lowest forms are almost identical 

 in appearance with the lowest plants, and they can only 



Pig. 8. Pi-otomonas amyli, greatly magnified. A, when encysted; x. germs or zo- 

 ospores ; y, food-mass. J5, germ freed from the parent-cyst. 6', D, older germs. E, 

 adult, encysted ; y, food ; s, projection inward of the cell-wall ; x, wall of the cyst ; t. 

 germs. After Cionkowski. 



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 (Fig. 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 (pseudopodid) or a network of gelatinous threads. 

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



