CHAP. I AMCEBA 231 



C, Aiiucba ^7-oiciis, a living specimen, showing large irregukir pseudopods, 

 nucleu.-, {nu), contractile vacuolt: {c. vac^, and two food vacuoles ij'.vac'), each 

 containing a small iiifusor (see p. 261) which has been ingested as food. The 

 letter a to the right of the figure indicates the place where two pseiidopods 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 the 

 succeeding figures (D, E, and G) it is seen in ojjtical section, and therefore 

 appears clear. 



D, an encysted Anitc-ba, showing cell-wall or cyst (tr), nucleus {tut), clear con- 

 tiMLtile \-acuole, and three microscopic plants (diatoln~^) ingested as food. 



E, AiiKcba protcui^ a living specimen, showing several large pseudopods {psd), 

 single luicleus {mi) and contractile vacuole {c. vac), and numerous food-particles 

 embedded in the granular endoplasm (x 330). 



F, nucleus of the same after staining, showmg a ground substance of achromatin, 

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

 membrane (x loio). 



G, Aiitixba verrucosa^ living specimen, showing wrinkled surface, nucleus (««), 

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



H, nucleus of the same, stained, showing the chromatin aggregated in the centre 



(X IGIO). 



I, AiiiLrba J>rotcus, in the act of multiplying by binary fission (x 500). (From 

 Parker's Biology : A, li, E, F, G, and H after Gruber ; C and I after Leidy ; D 

 after Howes.) 



Examined under the high power (P'ig. 67), the Amoeba 

 appears like a Uttle 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 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 crt-cps along slowly. The occur- 

 rence of anicedoid nioveuients 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 contains a nucleus (C — -H, ////), which is rendered more 

 apparent by staining and consists of chromatin and achro- 

 matin. I'he Amoeba is therefore a cell (compare p. 106). 



A very important difference is thus at once seen between 

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

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



