ii DIMORPHISM 35 



We see the very first step towards a division of labour in 

 the minute organism now under consideration. If we could 

 cut off a pseudopod of Amoeba the creature would be little 

 or none the worse, since every part would be capable of 

 sending off similar processes, and so movement would be in 

 no way hindered. But if we could amputate the flagella of 

 Haematococcus its movements would be absolutely stopped. 



Haematococcus multiplies only in the resting condition 

 (p. 28, and Fig. 3, B) ; as in Amoeba its protoplasm undergoes 

 simple or binary fission, but with the peculiarity that the 

 process is immediately repeated, so that four daughter-cells 

 are produced within the single mother-cell-wall (Fig. 3 c). 

 By the rupture of the latter the daughter-cells are set 

 free as the ordinary motile form ; sometimes they acquire 

 their flagella and detached cell-wall before making their 

 escape (D). 



Under certain circumstances the resting form divides into 

 eight instead of four daughter-cells, and these when liberated 

 are found to be smaller than the ordinary motile form, and 

 to have no cell-wall. Haematococcus is therefore dimorphic, 

 i.e., occurs, in the motile condition, under two distinct 

 forms : the larger or ordinary form with detached cell-wall 

 is called a megazooid, the smaller form without a cell-wall a 

 microzooid. 



D 2 



