58 



ZOOLOGY 



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

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



1.R aphid lofjhrys 



2.Nuclearia 



B.CIarhrulina 



Fig. 41. — Various forms of Heliozoa. 3a, the entire animal; 3b, the flagellula ; e. vac. 

 contractile vacuole ; g. gelatinous investment ; nu. nucleus pad. pseudopods ; tie. siliceous 

 skeleton ; ap. spicules. (From Btitschli'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. 



