2 ESSENTIALS OF ZOOLOGY 



Metaphyta. Many of the groups of Protozoa and Protophyta 

 are undoubted animals and plants respectively, but there are 

 other simple organisms which, whether we view them from 

 the standpoint of locomotion or method of feeding, or life 

 history, or the nature of the cyst, if any, in which they are 

 enclosed, cannot be satisfactorily relegated to either kingdom. 

 The student will find that such are claimed both by Botanists 

 and Zoologists. It is convenient therefore to think of a third 

 division of these simple organisms, the Protista, for the recep- 

 tion of the primitive and lowly types which are not definitely 

 animals or plants. 



The cell is defined as consisting of protoplasm with a nucleus, 

 and the nature of a free individual cell may be conveniently 

 studied in one of the Protozoa, the Amoeba. 



Amoeba. In the warm months Amoeba may be procured 

 from ponds with the help of a dipping tube or a fine net made 

 of silk, from water tubs, from soil, and they may also be got 

 at the shore. A drop of the water is placed on a microscope 

 slide and covered with a covering glass. Examined with a 

 low power at first, numbers of diatoms, desmids, and other 

 Protophytes will be found with Metazoa as Eotif era, Crustacea, 

 insect larvae and different kinds of Protozoa, many of them in 

 active movement; but search should be made for a small, 

 transparent, jelly-like creature, slowly moving in a peculiar and 

 characteristic manner, during which the shape is being con- 

 stantly changed. A close study of such a form will show that 

 the Amoeba consists of a jelly-like substance in the midst of 

 which is a small nucleus. The protoplasm of the nucleus has 

 been called nucleoplasm, and the extra-nuclear plasm the 

 cytoplasm. The distinction between the nucleus and cytoplasm 

 becomes more apparent when the animal is killed with certain 

 reagents, and especially if stained. The nucleus becomes plain ; 

 it stains readily and the cytoplasm does not. 



In the living Amoeba the cytoplasm is clear and denser 

 peripherally and is more fluid and granular internally, and may 

 therefore be resolved into ectoplasm and endoplasm. But 

 there appears to be little difference between the envelope of 

 ectoplasm and the inner endoplasm except that the former is 

 a surface film intervening between the plasm and the water. 



