167 
last pair of nephridia is affected. In a large specimen 
(250 mim. long) the sixth nephridium of the right side is 
normal, but the corresponding one of the left side consists 
of a tunnel only. Another specimen, 100 mm. long, has 
only five pairs of nephridia opening on the fourth to the 
eighth chetigerous annul, the sixth pair beimg totally 
absent. These cases seem to show that the funnel and 
the rest of the nephridium are, to some extent, inde- 
pendently formed, as in the examples mentioned above 
there are four cases in which the funnel is absent, and 
three in which a funnel only is present. 
In worms about 17 mm. long the nephridia, which are 
about “5 mim. long, have already assumed the adult form. 
The funnel is of considerable size and has well-marked 
lips, the dorsal one bearing from three to five short, blunt, 
conical elevations which later become the large spatulate 
processes of the older nephridium. The secreting portion 
of the first nephridium is a rather wide, almost S-shaped 
tube; that of the following nephridia is much wider and 
g ney 
sac-like. There is a rich vascular supply to all parts of 
the nephridium. In a specimen 44 mm. long the 
nephridia are about a millimetre in length (fig. 295). 
There is little change from the condition described above 
except that all the parts are larger; the dorsal lp of the 
nephrostome bears from four to seven small, blunt, conical 
processes. Nephridia of large specimens may attain a 
length of ‘8 mm. The funnel of such nephridia is large 
and its dorsal lip bears as many as thirty-two spatulate 
processes sub-divided distally into twelve to fifteen lobes. 
The lips of the nephrostome are lined by a single 
layer of ciliated columnar or cubical cells, supported by 
a thin film of connective tissue. here is a fairly sharp 
line of demarcation between the cells of the funnel which 
have no concretions, and the cubical, columnar, or pear- 
