Whitman the entire nephridial system (in the leech Clepsine) is formed by the differentiation of a continuous epiblastic band on each side.
Bergh (for Lumbricus and Criodrilus), whose figures show a derivation of the entire nephridium from mesoblast, and an absence of any connexion between successive nephridia by any continuous band, epiblastic or mesoblastic. A midway position is taken up by Wilson, who asserts the mesoblastic formation of the funnel, but also asserts the presence of a continuous band of epiblast from which certainly the terminal vesicle of the nephridium, and doubtfully the glandular part of the tube is derived.
The rhynchocoel is formed by a split which appears in the mesoblast surrounding the epiblastic pit which is the forerunner of the proboscis.
The excretory system is epiblastic in its origin.
The origin of the lateral organs has already been noticed; that of the nerve system is essentially epiblastic.