230 TORREY 



chyme. Finally, in the adult, the secondary body-cavity is 

 represented only by the gonad cavity. 



Although far from proven, the gonococle theory, toward the 

 development of which Meyer has done so much, seems to have 

 more points in its favor than any of the other theories dealing 

 with the origin of the mesoblast, and by it many apparent in- 

 consistencies in the origin and development of mesoblastic 

 organs may be explained. This is especially true, I think, if we 

 agree with Kleinenberg ('8i), Meyer ('90) and Eisig ('98) that 

 the sex cells — the foundation of the later coelomesoblast — 

 arose primitively (in a phylogenetic sense) before the somatic 

 cells had become resolved into the two primary germ layers, 

 as is the case at present in Volvox. 



