58 



ZOOLOGY 



SECT. 



complex. The protoplasm is distinctly divided into a central mass, 

 the medulla or endosarc (B, med.), in which the vacuoles are small, 



2. Nude aria 



3.ClaHiru.lma 



FIG. 41. Various forms of Helicrzoa. 3a, the entire animal; 8b, the flagellula ; c. rac. 

 contractile vacuole ; g. gelatinous investment ; nu. nucleus psd. pseudopods ; si: siliceous 

 skeleton ; sp. spicules. (From Biitschli's Protozoa, after Schulze and Greeff.) 



and an outer layer, the cortex or ectosarc (cort.), in which they are 

 very large. There are numerous nuclei (nu.) and chromatophores 

 (chr.), the latter coloured green by chlorophyll, the characteristic 

 pigment of green plants. 



