424 WILSON. [Vot. III. 
with these cords. In the short preliminary paper already 
referred to I stated that the entire nephridium, excepting the 
funnel, was derived as an outgrowth from the nephric cord, and 
was therefore of ectoblastic origin—a result in accordance 
(except as regards the funnel) with Whitman’s conclusions in 
respect to C/epsine, though this author did not follow the 
development far enough to determine the origin of the inner- 
most portion of the organ. This statement was based upon the 
following facts, all of which have been repeatedly verified in a 
number of species of Lumbricus, and are illustrated by Figs. 83- 
88, Pl. XXI. The funnel arises by the division of a large 
cell (f), which is differentiated at an early stage just at the 
anterior angle between the dissepiment and the somatic mesoblast 
(Figs. 83, 84), and manifestly arises from the mesoblast. Below 
and behind this cell a group of cells is formed out of which arises 
the body of the nephridium (zp.). In all its stages this group 
of cells can be traced directly into continuity with the cells of 
the nephric cord. The cells are disc-shaped and are arranged in 
a single row which ultimately becomes perforated through its 
centre to form the excretory canal. Almost from the very start 
these cells can be clearly distinguished from an investing layer 
of more or less flattened mesoblastic cells which are contin- 
uous with those forming the dissepiments and ultimately give 
rise to the peritoneal investment of the nephridium (Figs. 83, 
85, 88). 
In longitudinal sections the nephric cords present posteriorly 
exactly the same appearance as the neural cords and are sep- 
arated by a perfectly clear line from the mesoblast. Passing 
forward, however, this line fades away in the region of the 
youngest nephridia, so that it becomes extremely difficult to 
determine the relation of the nephric cord to the mesoblast. 
In this region the whole body-wall appears considerably thick- 
ened, and the only parts of the nephridia that can be positively 
identified, are the funnel-cells which form a regular series and 
are easily recognizable by their enormous nuclei. A little further 
forward, however, the relations can clearly be made out, and the 
cells are seen to be arranged in the manner already described. 
Whatever be its significance, there cannot be the slightest 
doubt that the nephridia, in their earliest recognizable form are 
connected in the manner described with the nephric cord, 
