CHAP. I AMCEBA 231 



C, Amoeba prottus, a living specimen, showing large irregular pseudopods, 

 nucleus (nu), contractile vacuole (c. vac), and two food-vacuoles (f. vac], each 

 containing a small infusor (see Chapter III) which has been ingested as food. 

 The letter a to the right of the figure indicates the place where two pseudopods 

 have united to enclose the food-vacuole. The contractile vacuole in this figure 

 is supposed to be seen through a layer of granular protoplasm, whereas in D, E, 

 and G it is seen in optical section, and therefore appears clear, (x about 300.) 



D, an encysted Amceba, showing cell-wall or cyst (cy), nucleus (nu), clear con- 

 tractile vacuole, and three microscopic plants (diatoms) ingested as food. 



E, Amceba proteus, a living specimen, showing several large pseudopods (psd), 

 single nucleus (nu) and contractile vacuole (c. vac), and numerous food-particles 

 embedded in the granular endopiasm. (x 330.) 



F, nucleus of the same after staining, showing a ground substance containing 

 deeply-stained granules of chromatin, and surrounded by a distinct membrane. 

 (x 1010.) 



G, Am&ba verrucosa, living specimen, showing wrinkled surface, nucleus (nu), 

 large contractile vacuole (c. vac), and several ingested organisms, (x 330.) 



H, nucleus of the same, the chromatin aggregated in the centre, (x 1010.) 

 I, Amceba proteus, in the act of multiplying by binary fission. ( x 500.) 

 (From Parker's Biology : A, B, E, F, G, and H after Gruber ; C and I after Leidy ; 

 D afier Howes.) 



Examined under the high power (Fig. 67), the 

 Amoeba appears like a little shapeless blob of jelly, 

 nearly or quite colourless, and closely resembling a 

 colourless blood-corpuscle or leucocyte of one of the 

 higher animals (p. 105). The central part of it, or 

 endoplasm, is granular and semi-transparent something 

 like ground-glass while surrounding this inner mass 

 is a border of perfectly transparent and colourless sub- 

 stance the ectoplasm. 



One very noticeable thing about the Amceba is that, 

 like the leucocyte, it is never of quite the same form for 

 long together, owing to the protrusion of pseudopods 

 (psd), by means of which it creeps along slowly. The 

 occurrence of amoeboid movements is alone sufficient to 

 show that it is an organism, or living thing, and no 

 mere mass of dead matter. Moreover, it consists of 

 protoplasm, and encloses a nucleus (C H, nu} contain- 

 ing chromatin and rendered more apparent by staining. 

 The Amceba is therefore a cell (compare pp. 106 and 

 no). 



A very important difference is thus at once seen 

 between the -Amreba and the frog : the Amceba is 

 unicellular, i.e., it consists of a single cell, while the 



