22 



Invertebrate. 



Fig. 10. 



Class 2. Protoplasta. In the slowly running 

 waters of ditches, or in bog pools, are found curious 

 creatures in many respects reminding us of the naked 

 Rhizopods. These amoebae as they are called, are 

 little masses of protoplasm, moving and taking food 

 by means of pseudopodia. On close inspection many 

 particulars will be noticed, in which they differ from 

 those simple creatures which we have already ex- 

 amined. Thus their pseudopodia are blunt, and do 

 not freely coalesce, on touching each other ; the 

 granules and vacuoles are not uniformly distributed 

 through the protoplasm, but are for the most part in 

 the central region, while the outer protoplasm is 

 fir.ner. We also notice a denser central spot in the 



body, to which the 

 name nucleus is given, 

 as can be seen in each 

 component mass of 

 Magosphsera (fig. 9) ; 

 and one or more 

 little clear spaces may 

 be seen occasionally 

 to contract and ex- 

 pand alternately. 

 Thus in the group of 

 organisms of which 

 the" pseudopodia, amoeba is the type, 

 protoplasm has be- 

 come partly differentiated, that is, some parts have 

 assumed characters which the simple protoplasm 

 did not possess. On account of this first trace 

 of the development of tissue we call this group of 



One of the Sun 



anima _ 



nuclei, vacuoles, &c. 



