INFLAMMATION AND PHAGOCYTOSIS 133 



transparent and thus easily observed, have neither nervous 

 system nor vessels nor muscles : they react towards a pene- 

 trating foreign body by an accumulation of amoeboid meso- 

 dermic cells. In a larger larva, Bipinnaria asterigeria, the cells 

 of the mesoderm can be seen engulfing particles of carmine or 

 of indigo and surrounding a splinter or a drop of blood with 

 masses of cells equivalent to a plasmodium. They also engulf 

 bacteria introduced under their outer skin. 



In all these cases inflammation occurs without blood or 

 blood vessels. Among the Annelids which possess a closed 



monospotne 



FIG. 47. Daphnia infected by Monospora. FIG. 48. Different stages of 

 (Metchnikoff.) Monospora. (Metchnikoff.) 



vascular system, the reaction against foreign bodies takes place 

 in the same way without any intervention of the blood vessels. 



In LumbricuS) whose male sex-glands are infected by 

 gregarines, there is a struggle between the two organisms, the 

 gregarine encysting itself and becoming surrounded by an outer 

 covering of protective chitin, while the amoeboid cells sur- 

 rounding it join together and form a sort of armour-plating 

 which stifles it. The blood-vessels remain inactive. 



For an example of parasitism exactly parallel to an infectious 

 disease there is nothing better than to observe Daphnia magna 

 being invaded by a microscopic fungus, the Monospora bicuspi- 

 data. The motile cells engulf the spores of the mould and 



