16 



PHYSIOLOGY 



CHAP. 



are little naked protoplasmic bodies with no enclosing membrane, 

 having often a distinct nucleus. These put out in all directions 

 projections of their body- substance, or pseudopodia, which are 

 continually changing in shape. The majority of cells, however, 

 possess a constant form, whether the protoplasm be enclosed in 



FIG. 5. Chondrioderma di/orme, life phases. (Strasbtirger.) a, dry spore ; b, turgid spore ; c, d, 

 dehiscence of spore-membrane and escape' of cell-contents ; e,f, g, transformation of primitive 

 spore into piriform and flagellate zoospore ; h, zoospore passing into state of myxamoeba ; 

 i, i, young myxamoebae ; k, k, adult myxamoebae ; ^adherent myxamoebae ready to fuse ; m, 

 young plasmodium ; n, portion of adult reticulated plasmodium. 



a membrane or not. Many permanent forms repeat the temporary 

 shapes assumed by the amoeboid cells. 



The size of the cells, again, varies greatly, though they are 

 almost always of microscopic dimensions. The smallest Bacteria 

 measure only a few thousandths of a millimetre, while the largest 

 Amoebae exceed a tenth of a millimetre. The cells of the higher 

 organisms, Man included, are rarely more than eight hundredths 



