W. A. HASWLIIJ.. 
21t) 
approximately straight, and run in all cases from before back^ 
wards to open on the ventral surface. 
In the occurrence of a pair of nephridia in the liead region 
in the adult condition, Stratiodrilus differs not only from 
H istriobdella, but from every other group with which it 
might be supposed to have affinities. The extension of each 
of these head-nephridia in a loop across the middle line is alsa 
a very special feature. Perhaps this may be explained by the 
very intimate relationship that appears to exist between these 
loops and the structures which I havm called the cervical 
glands, and which, as I have already suggested, may belong-' 
to the nephridial system. 
Both Foettinger and Shearer describe the nephridia as 
intra-cellular tubes, and the former definitely states (p. 471) 
that the section has the appearance of a rounded nucleated 
cell presenting an aperture in its cytoplasm. But such a 
description does not convey an accurate impression of the- 
actual nature o£ these oi-gans — at all events as they occur in 
Stratiodrilus. The tissue through which they run is not 
cellular in the strict sense of the term. It consists of a 
differentiated part of the nucleated coelenchymatous tissue 
not divided into cells, the outer portion of which has the 
function of the mvoblastic tissue for the muscular fibres of 
the body, while the inner forms a thin layer investing the 
gut and having the relations, though not the structure, of a 
splanchnic epithelium. Throughout a whole series of sectious^ 
of the caudal region there are no nuclei that have any special 
and intimate relationships with the walls of the nephridial 
tubes. Further forwards in the same pair of nephridia, where 
the walls have assumed greater definiteness, and where, at 
long intervals, nuclei appear in this wall, there is still no 
question of cells, but simply of a greater condensation of the 
tissue around the lumen of the nephridia. 
Foettinger describes the vibratile structures in the interior 
of the nephridia as cilia. But, as Shearer has pointed out, 
they have much more the appearance of elongated flagell;i. 
The relationships of these are very difficult of determination. 
