PT. ii. CH. i AMCEBA 231 



C, Amoeba proteus, 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. 



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

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



E, Amoeba protens, a living specimen, showing several large pseudopods (psd), 

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

 embedded in the granular endoplasm ( 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 TOIO). 



G, Amoeba 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, Amoeba 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 after 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-cor- 

 puscle 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 surround- 

 ing this inner mass is a border of perfectly transparent and 

 colourless substance the ectoplasm. 



One very noticeable thing about the Amoeba 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 occur- 

 rence 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, mi) containing chromatin 

 and rendered more apparent by staining. The Amoeba 

 is therefore a cell (compare pp. 106 and no). 



A very important difference is thus at once seen between 

 the Amoeba and the frog : the Amoeba is unicellular, i.e. it 

 consists of a single cell, while the frog is, as we have seen, 



