6 PROTISTS AND DISEASE 



when first they appear in the matrix of the chromidium, 

 we can see in them no differentiation of structure ; each 

 gametoblast is a particle of apparently structureless 

 material. For such substance Haeckel used the term 

 " plasson." This totipotential form of living matter has 

 been defined in an article on the Proteomyxa by S. J. 

 Hickson : 



" It seems probable then that the protoplasm of the 

 Proteomyxa really represents the protoplasm of the higher 

 Protozoa and Metazoa plus the substance of the nuclei. 

 It is the substance which van Beneden, in 1871, proposed 

 to call the ' plasson,' that is, the formative substance which 

 is capable of becoming, either in ontogenetic course or in 

 phylogenetic course, monocellular elements, after that the 

 chemical elements of the plasson have been separated to 

 constitute a nucleus and a protoplasmic body. '' 



Haeckel was right in that non-nucleated organisms 

 exist, but those we know have also phases in which they 

 have nuclei ; therefore he was mistaken in assuming that 

 his cytodes were of necessity devoid of nuclei at all stages 

 of their life-history ; indeed, many of them have been found 

 to have nuclei at all stages. 



In estimating Haeckel' s work we should remember that 

 he was the first to note the inception of foreign particles by 

 leucocytes ; the bearing of this function on immunity was 

 first indicated by Carl Roser in 1881, and later named 

 phagocytosis by Metchnikoff. 



