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 ( Vorticetta.) 



CLASS I. MotfERA (Moners). 



General Characters of Moners. This group comprises 

 the simplest forms of Protozoans, whence the name Monera 

 (novTfpe?, simple). The lowest forms are almost identical 

 in appearance with the lowest plants, and they can only 



Fig. 8. Protomonas amyli, greatly magnified. A, when encysted; a*, germs or zo- 

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

 adult encysted ; y, food ; , 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 Amceba, 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 



