tion in its destiny and consequently a change in its 

 habits and in its very form. That factor arose: it 

 was the finding of the floor of the sea. 



This was a momentous event in the history of 

 the echinoderms as well as in the life of Dipleur- 

 ula; for such is the name that science has given to 

 our more than hypothetical creature. Now ensued 

 those changes in the structure of the latter which 

 inaugurated the former as a phylum. As the sea- 

 bottom could be apprehended only by the sensory 

 end, the foremost, it was by that end that Dipleur- 

 ula affixed itself, eventually becoming perma- 

 nently attached; not at the tip, however, precisely 

 where the sensory organ was, as that would inter- 

 fere with its functioning; but slightly to one side. 

 Thus, with Dipleurula literally standing on its 

 head, begins the first echinoderm. 



But see what now happens. The mouth travels 

 upward — the inevitable result always to be ob- 

 served in such instances — toward the vent, pro- 

 ducing as a consequence a coiled gut. As a further 

 consequence of this upward migration of the mouth 

 and the concentration of the intestinal tract and 

 other major organs in the uppermost portion of the 

 body, the animal becomes pear-shaped. Then the 



[93] 



