VII 



ANNELIDA 



159 



to a chain of cells, and this cell chain becomes hollowed out and 

 forms a tube. Its most internal cell projects into the coelomic 

 cavity between the coelomic cells forming one side of the septum, and 

 forms the greater part of the coelomic funnel of the nephridium. 

 The lower lip of the funnel is constituted by one huge cell belonging 

 to the coelomic wall. This cell (f.c, Fig. 118) only divides once and, 

 as is well known, the ventral lip of the nephridial funnel in the adult 



coe 



FIG. 118. Two longitudinal sections through the ventral portion of an embryo of 

 Criodrilus Incuum. (After Staff.) 



A, section through a younger embryo in which the nephridial string is not yet broken into cell- 

 gronps destined to give rise to the nephridia. B, section through an older embryo in which the 

 nephridial string is broken into groups. Letters as before. In addition, bleph, blepharoblasts, i.e. 

 basal granules of cilia in the funnel of nephridium ; ch, rudiment of chaeta ; eft.s, group of ectoderm 

 cells destined to form the chaeta sac ; /, funnel of nephridium ; f.c, funnel cell, i.e. the large meso- 

 dermic cell which, according to Staff, forms the ventral lips of the nephridial funnel ; Af.T, teloblast 

 of mesodennic band the two dotted lines indicate the hinder part of this band which curves outwards 

 so that it does not lie in the plane of the section ; neph.st, nephridial string of cells. 



worm is quite different from the dorsal lip, and consists of only two 

 cells. The result of this investigation is therefore to uphold Goodrich's 



view. 



HIRUDINEA 



The development of Hirudinea is interesting for two reasons, first, 

 because it establishes the Annelidan affinities of this group, which 



