THE GIANT EARTH-WORM OF GIPPSLAND. Ze 
There is, however, a very curious, and, at the same time, instructive series of 
gradations to be seen if the nephridia be carefully studied in situ. Thus in worms 
containing some 500 segments, the large nephridia, with internal openings, can be 
recognised through some 220 segments, counting from the posterior end. In front 
of this no internal openings can be detected, but for some 15-20 segments anteriorly, 
a nephridium larger than the rest, but gradually decreasing in size, can be recognised. 
It does not, however, stand alone, but forms one of a group of nephridia, the large 
individual one, on passing anteriorly, gradually decreasing in size and predominance as 
the group increases until, after twenty segments or thereabouts, the group remains, 
but no one nephridium is larger than the rest. This ventral group, as the anterior 
end is reached, tends to merge more and more into the general ring of small nephridia 
(though generally detectable by careful examination), which at the same time becomes 
more widely spread over the body wall, until, in the clitellar region, the whole body 
wall becomes covered with the smaller nephridia. 
THE SPECIALIZATION IN NEPHRIDIA APPEARS THUS TO CoMMENCE AT THE PosTERIOR 
Ewp, and To Pass Grapuatty Forwarps, tHe Anterior Brine 1n 4 Muce More 
Primitive Conpition THAN THE Posrmrior Eyp or tHE Bopy. 
Structure of the Nephridia. 
1.—Small nephridia.—These, when cut in section, are seen to have the structure 
typical of the nephridia of earth-worms. Lach consists of a coiled tube with an 
intra-cellular duct (Fig. 18). The tube is surrounded with an investment of a large 
number of connective tissue cells, the boundaries of which cannot be detected, though 
their nuclei are clearly seen scattered about irregularly. The effect is produced of a 
somewhat homogeneous mass surrounding the tubules and continuous with the body 
wall. This agrees closely with the structure, described by Bennamas existing in the part 
of the nephridia of Microcheta rappt, farthest away from the vesicular end. There is 
also a thin definite layer of tissue surrounding closely the tubules, consisting of fibres 
with nuceli (ct. neph.) In the connective tissue, ramify and branch a great number 
of minute blood-vessels (bv.), which, as usual in earth-worms, are seen when the 
nephridium is viewed as a whole, to form an investing network over the nephridial 
tubules. 
The latter have the usual form of a series of large cells, placed end on, and 
pierced by an intra-cellular duct. Their nature makes them at once easily distinguish- 
able from other structures in the body. The cell consists of a homogeneous ground 
work, in which are scattered minute granules, so set as to produce in section the 
effect of lines radially arranged with regard to the duct. The bounding line of the 
latter is very clear and distinct. This structure again resembles exactly that figured 
by Breyuam in Microcheta rappi and others, and by Bepparp in Pericheta aspergillum 
and Acanthodrilus multiporus. Where the nephridium joins the body wall the duct passes 
into the latter (Fig. 18) sometimes directly, sometimes after running along for some 
