22 ON THE ANATOMY OF MEGASCOLIDES AUSTRALIS, 
investment for the body walls. (Fig. 1 and fig. 22.) They are absent in the very 
median dorsal and ventral lines, though they extend very closely on to these. On 
the ventral surface, the nerve cord separates the nephridia of the two sides. In Fig. 
22 is represented a portion of the dorsal body wall, cut away from the hinder clitellar 
region, where the septa are thinner than in front. Three segments are shown, and 
in the median line is seen a distinct groove, which separates the nephridia of the two 
sides, and out of the roof of which open the dorsal pores. 
Passing backwards, the nephridia lessen in number, and after about the 25th 
seoment, form simply a ring round the posterior region of the segment (Fig. 21) 
between the two posterior and the anterior pairs of nerve branches. ‘They are more 
or less irregularly scattered in the ring, which in the middle and posterior parts of 
the body seem to be continuous across the mid-dorsal line, to be only broken 
ventrally where the nerve cord runs. 
It is quite impossible to count the number of these small nephridia, of which 
certainly more than a hundred are present in each clitellar segment. 
None of them have any trace whatever of an imternal opening, though I have 
searched for such most carefully, both by means of examining numerous whole 
nephridia, and large series of sections. 
2.—A series of much larger nephridia, which are only present in the posterior 
region of the body, and occur in the same segments with the smaller nephridia 
(Fig. 21), from which there is no difficulty in distinguishing them—(1) On account 
of their position ; (2) on account of their size, and (3) on account of their possessing 
internal openings. 
There is only one pair of these larger nephridia in each segment, and each lies 
close to the ventral nerve cord, occupying the anterior part of the segment, whereas 
the smaller nephridia are placed in the posterior. Each is attached to the body wall 
in front of the anterior nerve branch, and not very far behind the septum. There is 
no difficulty in recognising on the anterior wall of every septum, close to the median 
ventral line, a small ciliated funnel, which has the appearance during life of a minute 
white speck, attached by a short stalk to the septum. (Fig. 21, neph. 7. 0.) With 
care, it can be dissected away, and under the microscope is recognisable at once as a 
ciliated trumpet-shaped opening, the lower lip of the trumpet being somewhat shorter 
than the upper. (Fig. 26.) The opening leads back into a tubular duct, in which 
cilia may be seen working, and which is evidently continuous with the anterior 
prolongation of the large nephridium. The latter consists of two parts—(1) A 
smaller straight one (7.), and (2) a larger coiled portion, which seems to vary 
somewhat in shape and size, and to consist of a large number of smaller coiled tubules 
aggregated together, and enclosed in a common surrounding of connective tissue. 
As above said, these large nephridia are only found in the posterior region of 
the body, and are quite wanting anteriorly, where the smaller ones are alone 
present. 
