162 THE KIDDLE OF THE UNIVERSE. 



way in both cases — the cells of the tissue (the regular, 

 orderly structure of cells) transmit the stimuli they 

 have received in one part, and thus provoke move- 

 ments of other parts, or of the whole organ. This 

 transmission of stimuli has as much title to be called 

 " psychic activity " as its more complete form in the 

 higher animals with nerves ; the anatomic explanation 

 of it is that the social cells of the tissue, or cell-com- 

 munity, are not isolated from each other (as was 

 formerly supposed), but are connected throughout by 

 fine threads or bridges of protoplasm. When the 

 sensitive mimosa closes its graceful leaves and droops 

 its stalk at contact, or on being shaken ; when the 

 irritable fly-trap (the dionsea) swiftly clasps its leaves 

 together at a touch, and captures the fly ; the sensa- 

 tion seems to be keener, the transmission of the 

 stimulus more rapid, and the movement more energetic, 

 than in the reflex action of the stimulated bath-sponge 

 and many other sponges. 



B. The soul of the nerveless metazoa. — Of very 

 special interest for comparative psychology in general, 

 and for the phylogeny of the animal soul in particular, 

 is the psychic activity of those lower metazoa which 

 have tissues, and sometimes differentiated organs, but 

 no nerves or specific organs of sense. To this category 

 belong four different groups of the earliest coelen- 

 terates : (a) the gastrseads, (b) the platodaria, (c) the 

 sponges, and {d) the hydropolyps, the lowest forms of 

 cnidaria. 



The gastrceads (or animals with a primitive gut) 

 form a small group of the lowest coelenterates, which 

 is of great importance as the common ancestral group 

 of all the metazoa. The body of these little swimming 

 animals looks like a tiny (generally oval) vesicle, 



