LIVING SUBSTANCE 



alga Euastrum (Fig. 19, a) represents such a cell with lobate 

 processes, and the ganglion-cells in the central nervous system 



Fig. 18.— a Egg-cell from the ovaiy of a sea-ui-chin. (After Hertwig.) 6, Epidermis-cells from 



the frog. 



of man, the brain and spinal cord, which give origin to the nerve- 

 fibres, possess constant processes which appear exactly like the 



Fig. 19. — ft, Euastmiii, a unicellular alga from the group of the Vrayaidictceai. 

 (After Haeckel.) 6, Ganglion-cell from the human spinal cord. (After 

 Gegenbaur.) :, Cell-body ; /i, nerve-process (axis-cylinder process). 



pseudopodia of many ihizopod cells (Fig. 19, V). 

 Other cells, the ciliated cells, have upon their sur- 



