24 ZOOLOGY. 



its body. The Amoeba reproduces its kind by simple di- 

 vision, as seen in Amoeba splic&rococcus Haeckel (Fig. 11). 

 This species, unlike others, so far as known, becomes encysted 

 (H), then breaks the cell-wall and becomes free as at A. 

 Self-division then begins as at C, the nucleus doubling it- 

 self, until at D a and D b we have as the result two individ- 

 uals. 



Order 1. Foraminifera. Besides Amoeba, several other 

 forms, either naked or shelled, produce, by division of an in- 

 ner portion of the body, numbers of ciliated young, as in 

 the naked Pelomyxa, in certain many-chambered Fora- 

 minifera, and in Collosphce- 

 ra. An example may be 

 seen in the European Pelo- 

 myxa palustris Greef (Fig. 

 12). This creature lives in 

 the mud at the bottom of 

 fresh-water pools, and when 

 first seen resembles little 

 dark balls of mud a milli- 

 metre in diameter. Instead 

 of one nucleus, there are 

 numbers of them, and nu- 

 merous contractile vacuoles 



Fig. 12. Pelomyxa palustris. A, a, clear ,,,, , .,, a .-, , ,, 



cortical portion; b. diatoms enclosed in the tilled With a mild, together 

 body-mass. B, amcebu-like bodies originating ,-t i mi 



from the nuclei, which after leaving the body With SplCuleS. The JOUHg 



pass into monad-like forms, 0; n, nucleus; ., O j. fl-.-f om/^Ko lil / 7?^* 



c, contractile vesicle. -After Greef. &re at nrst amoeba-like (>), 



originating as " shining 



bodies," which have resulted from the self -division of the 

 nuclei. These amoeba-like bodies finally assume an active, 

 monad-like stage C, and move about by means of a cilium 

 or lash. 



We now come to the shelled Amoebae, or genuine Forami- 

 nifera. A common type is Arcella, which secretes a one- 

 chambered silicious shell, found in fresh water, and a 

 representative of the monothalamous, or one-chambered, 

 Foraminifera; while the many-chambered forms are 

 marine, of which Globigerina bulloides (Fig. 13), found 

 floating on the surface of the ocean, with its pseudopodia 



