... feeding, the flagella are positioned around specialised areas of the cell (a gullet) and push food towards or into this gullet (fig 2.7, Ridge 2001) Although most cells have one nucleus (fig 1), many have more. This can range from two, as in Giardia lamblia (fig 3), to several hundred. Polystomella sp. have one large somatic nucleus for everyday use by the cell and 3 smaller nuclei used only in reproduction (fig 2.8, Ridge 2001). Pelomyxa palustris, another non-flagellate, has nearly 2000 nuclei and is one of the largest protoctists; it may exceed 5mm in diameter (Guide to Living Organisms) (fig 2.2, Ridge 2001). Polyploidy is seen in some organisms, e.g. Heliospherea inermis (fig 4). Many organisms strengthen the cell, allowing for increased size by having a cytoskeleton. Actionopods such as Heliospherea inermis (fig 4) further strengthen this cytoskeleton with silica in a lattice formation. Endoskeletons may be simple strips of ...

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