PROTISTS AND DISEASE 



examples of two modes of origin of new nuclei, and we 

 see a great contrast. In Fig. 1 are seen three stages of 

 regular mitosis in a protist : chromosomes, centrosomes, 

 spindle, etc. In Fig. 2 new nuclei are being formed from a 

 chromidium, a segregated mass of akaryote germ-plasm that 

 has been extruded from the nucleus of its parent protist 



FIG. 1. STAGES OF MITOSIS IN ACANTHOCYSTIS ACULEATA, A HELIOZOON : 

 a, metaphase ; b and c, anaphases. (From Doflein, after Schaudinn.) 

 From Part III. 



and lies in the cytoplasm, equivalent to a metazoan ovotestis. 

 In the vegetative part of its life Mastigella undergoes mitosis 

 quite like that of Acanthocystis, Fig. 1. 



Chromidia. An akaryote structure destined to produce 

 gametes illustrates one kind of chromidium, the generative ; 

 the other kind is the vegetative. Generative chromidia have 

 been recognised (H. Wager) as of two kinds ; firstly, those 

 that replace nuclei, and secondly, those that are capable of 

 being re-formed into nuclei. Of the latter the garnet o- 

 genetic chromidium of Mastigella is an example ; in this 



