THE GIANT EARTH-WORM OF GIPPSLAND. 45 
Benuay, in his valuable general summary* of the various organs of earth-worms, 
dealing with the question of the homology of the genital ducts and nephridia, says 
that the modification which the nephridium undergoes to form a genital duct consists 
either in— 
(a) A fusion of a series of nephridia, or 
(b) A disappearance of a part of the nephridium, or 
(c) A shifting of the position of the pore. 
Now, so far as our present information goes, we have no actual evidence of any 
one of these occurrences taking place to form a genital duct. Brnuam says, “In the 
case of the male duct, each of these modifications is exhibited. In the somites, in 
which le the ciliated rosettes, the external extremity of the nephridium has 
disappeared. In the somite carrying the male pore, the funnel region of the 
nephridium is absent, whilst in the intervening somites both these regions have 
aborted, and a fusion of these various parts has taken place to form the more or less 
elongated duct.” Now, as above stated, the whole of the male duct is inter-cellular 
in nature, whereas, according to this suggestion, the only parts of the nephridia 
which are inter-cellular have disappeared, save the ciliated rosettes at the 
commencement of each tube and the external openings at their terminations, leaving 
in the intermediate segments merely the typical intra-cellular parts of the nephridia 
to form a duct, the vas deferens which is characterised by its uniformly inter-cellular 
character ! 
Other difficulties again arise in connection with the male duct, as, for example, 
the presence of two perfectly distinct ducts running side by side in Megascolides, and 
of even “four separate sperm ducts, each with its external pore in Acanthodrilus and 
Monihigaster.”+ 
Sumilarly m the oviduct all intra-cellular portions of the duct must have 
disappeared, and the same again with the spermathece; in fact, the total 
disappearance of what forms the most characteristic portion of the nephridia is, even 
on the assumption that when converted into genital ducts the nephridia lost their 
primitive function, a very remarkable occurrence. If this difficulty stood alone it 
need not perhaps be regarded as an insuperable objection, but there is in addition the 
second class of evidence derived from an investigation of the respective development 
of the two sets of structures in various earth-worms. 
The latter we may, simply as far as their nephridia are concerned, divide into 
three sets :— 
(1) Those with very numerous small nephridia in each segment, with no internal 
but many or several external openings in each segment, which may or may not have 
a definite relationship to the sete. (Pericheta, Acanthodrilus, &c.) 
* Q.J.M.S., Feb. 1886, p. 265. + Benuam. Op. cit., p. 260. 
