KHIZOPODA. 



CHAPTER 11. 



RHIZOPODA. 



I. Type of the group : Amoeba. — 2. Nature of Rhizopoda. — 3 

 Rhizopoda allied to Amoeba. — 4. Classification of Rhizopoda. — 5 

 Foraminifera. — 6. Classification of Foraminifera. — 7, Unilocular 

 Foraminifera. — 8. Polythalamia. — 9. Structure of the shell in 

 Foraminifera. — 10. Technical terms. — 11. Distribution of Fora- 

 minifera in Space. — 12. Distribution of Foraminifera in Time. — 

 If. Size of Rhizopoda. — 14. Development of Rhizopoda. 



I. Type of the group : Amveba. — In order 

 to understand the true nature of the Rhizopoda it 

 will be necessary, in the first place, to become 

 acquainted with those characters which are fur- 

 nished by the examination of some typical form. 

 The most easily procured of all Rhizopods is, 

 perhaps, the ATYioeha, a minute animal not un- 

 common in most ponds or infusions {fig* i). 



WTien first placed under the microscrope the 

 Ainoeba presents the appearance of a globular mass 

 of semitransparent jelly, destitute of any apparent 

 organisation. This seemingly helpless being soon, 

 however, commences to show signs of life by push- 

 ing out in various directions portions of the jelly- 

 like substa,nce of which its body is composed. By 

 expanding one of these prolongations, and then 

 drawing after it (or rather into it) the remainder 

 of its body, the Amoeba slowly advances, in a some- 

 what irregular manner. The gelatinous processes 

 thus protruded have received the name of ' pseu- 

 dopodia,' from their subservience to the function 

 of locomotion. But this is not the only pui'pose 

 which they serve. Should the Amoeba, in its pro- 

 gress through the water, come in contact with any 



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