152 MOVEMENTS OF THE SLIME MOULDS 



of the soft plastic body or more commonly the body may possess 

 a delicate thread or cilium (plu. cilia) (Fig. 89, C). These 

 ciliated bodies are called zoospores. The cilium is a highly 

 sensitive organ which by rapid and rhythmical movements, 

 somewhat like the movements of the arms in swimming, beats the 

 water and thus drives the body along. While in this condition 

 the zoospores are rapidly multiplied owing to the repeated split- 

 ting of the little bodies into two similar parts. Finally this 

 greatly increased number of individuals begins to come together 

 in small groups (Fig. 89, D) which in turn merge and so form 

 large slimy masses termed plasmodia (sing, plasmodium) which 

 are quite destitute of all walls and consist of a great number of 

 nuclei surrounded by a watery cytoplasm (Fig. 89, E). You will 

 often find this plasmodial stage of the slime mould on the under 

 side of rotting limbs or bits of wood in the forest as a sticky mass 

 resembling in consistency the white of an egg. The mucilaginous 

 character of the plasmodium accounts for the name slime mould 

 popularly applied to these plants, also for the term myxomycetes, 

 from myxos, slime, and myces, mould or fungus. 



The plasmodium possesses a sensitiveness or capability of 

 responding to external stimuli to a degree that is remarkable 

 when we consider the extreme simplicity of these plants. For 

 example, it avoids too strong a light and slowly moves toward 

 moisture and food. This accounts for your failure ordinarily 

 to notice it since it seeks the darkness and food in decaying 

 logs or the under surface of sticks and leaves. The motion is 

 brought about by little arm-like branches that flow from the 

 jelly-like plasmodium and finally the entire plasmodium will 

 slowly follow along these lines with a complicated streaming 

 movement (Fig. 89, E). If bits of wood containing some of 

 the plasmodium are placed in a damp chamber in the dark after 

 a time the plasmodium will be seen creeping up the sides of the 

 moist dish in a complex skein-like mass or if a glass slide, down 

 which a very meager amount of water is slowly allowed to trickle, 

 is brought in contact with the plasmodium it may be observed 

 creeping up the slide toward the source of the water supply. 

 The slime moulds do not contain chlorophyll and are therefore 



