408 
EDWIN S. GOODRICH. 
between the large bands above the ventral groove (fig. 36). 
From the extreme anterior end of the oesophagus muscles 
extend to the base of the median tentacle over the brain; 
similar muscle-fibres pass through the brain to the lateral 
tentacles. The dorsal longitudinal muscles are attached 
to the ventral wall of the pygidium behind. Some muscles 
run obliquely through the coelom from near the nerve-cords 
to the body-wall, where they are attached chiefly in the 
neighbourhood of the parapodia (fig. 30). Special muscles 
are fastened to the pharynx, and others run from the body- 
wall to the chaeta-sacs, whereby these can be to some extent 
drawn in and out (fig. 8). No distinct layer of muscles can 
be made out in the wall of the stomach or intestine, nor can 
circular muscles be seen in the body-wall. 
The Nephridia. 
Nephridia were first seen in Nerilla by Claparede, who, 
however, misunderstood their structure ( 3 ). He believed 
them to have no internal opening, and to open forwards 
to the exterior in the centre of the ciliated lateral patch. 
Miss Pereyaslawzewa denied the existence of nephridia, mis- 
taking them for parasites. De Beauchamp has given a 
very brief, but correct, account of their disposition and 
structure (2). 
There is a marked difference between the sexes in the 
number and distribution of the nephridia. While in the 
female there are four pairs of nephridia, in the male there 
are only three pairs. Those of the male are situated in the 
second, fifth and ninth segments (fig. 10), those of the female 
in the second, fifth, sixth and eighth segments (fig. 9). The 
first and second pairs of nephridia are the same in the two 
sexes; but the last pair differs not only in position but also 
to a slight extent in structure. De Beauchamp seems to have 
missed the nephridia in the ninth segment of the male. All 
the nephridia are simple, and built on essentially the same 
plan. The nephridiopore is placed on the ventral surface 
about halfway between the base of the parapodium and the 
