24 



ZOOLOGY. 



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

 vision, as seen in Amoeba sjrficerococcus Haeckel (Fig. 11). 

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

 (B}, 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 CoIIospJiop- 

 ra. An example may be 

 seen in the European Pelo- 

 myxa palusfris 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. la. Pelomyxa pali/^tris. A, a, clear ,,,, , .., ,, . -. ,, 



cortical portion; />. diatoms enclosed in the filled With a 11111(1, together 

 body-mass. B, amoeba-like bodies originating -,i i rn 



from the nuclei, which after leaving the body With SplCUlCS. J lie yOUllg 

 pass into monad-like forms, C ' ; it. nucleus; j. fl j. ,-,,, pi IjVp / R\ 



4, contractile vesicle. After Greef. 1Kt \ n )> 



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 Amcebse, 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 bulloidex (Fig. la), found 

 floating on the surface of the ocean, with its psendopodia 

 * See Leidy's Fresh water Rhizopods of North America, 1879. 



