350 THÉEL, SKELETOK OF THE ECHINODERMS. 



whicli deposit unorganic substances, and probably they raay be 

 considered to have their origin in the latter. Like these they are 

 unprovided Avith a cell-wall, possess evidently a single nucleus 

 and present anioeboid movements though in a much higher and 

 more active degree than the calciferous ones. It almost conveys 



Changes of form of an amoeboid cell dissolving the posterior detached end of a calcareous 



rod of a mature pluteus. 1—8, different views of the operative cell up to the time when 



the calcareous piece has become parted in two and highly reduced by the solvent faculty of 



the cell. Drawn from a living pluteus. Highly magnified. 



1 was drawn at 10.30 a. m. 



5 12 noon. 



7 12.22 p. m. 



8 12.35 p. m. 



the impression • that the process of absorption demands a much 

 more intense labour on the part of the cell than that of deposi- 

 tion. If observed under a high power of the microscope, the 

 cell is seen gradually to protrude portions of its clear protoplasm 

 in one or more directions simultaneously. These pseudopodia 



