﻿PLANTS AND ANIMALS 



Aristotle and other ancient writers, it had 

 been observed that sponges grow attached 

 firinl}' to rocks by root-Hke extensions, yet 

 possess some feehng. that sea-cucumbers 

 {Holotburin) and sea-slugs (Ctenopbora), 

 although having 

 freedom of move- 

 ment, seem to lack 

 feeling, and in this 

 respect behave 

 like plants, that 

 sea-anemones are 

 fixed objects, yet 

 are sensitive like 

 animals, and that 

 many other living 

 things have char- 

 acteristics that 

 make them in like 

 manner uncertain 

 of classification. 

 Aristotle's conclu- 

 sion from these 

 facts, that "na- 

 ture passes grad- 

 ually from the insentient over to the sentient 

 through forms that truly live but are not 

 animals, " only ne°ds the substitution of 

 Mycetozoa and some Flagellata for the Po- 



FiG. 23 — A sea cticnnibcr with 

 extended branched ten t acles. 

 (After Glaus.) 



