24 



ZOO LOG f. 



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

 vision, as seen in Amceha splioirococcus Haeckel (Fig. 11). 

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

 {B), then breaks tlie cell-wall and becomes free as at A. 

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

 self, until at i? a and Dl vie have as the result two individ- 

 uals. 



Order 1. Foraminifera. — Besides Amcela, 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 CollosphcB- 

 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 

 filled with a fluid, together 

 with spicules. The young 

 are at first amoeba-like [B), 

 originating as " shining 

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

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

 monad-like stage O, 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 GloMgerina iulloides (Fig. 13), found 

 floating on the surface of the ocean, with its pseud opodia 



Fig. 12,— Pelonwxa palmiiis. A, a, clear 

 cortical portion; o, diatoms enclosed in ttie 

 body-mass. 3, amceba-like bodies originating 

 from the nuclei, Avhich after leaving tlie body 

 pass into monad-like forms, C; n, nucleus; 

 c, contractile vesicle. — After Greef. 



