36 ON THE ANATOMY OF MEGASCOLIDES AUSTRALIS, 
quite independent of the adult ones, Wuirman states that they are not. Brpparp 
further points out that the larval nephridia of Oligochete discovered by Vuspovsky 
“occur at the anterior end of the body, where no permanent nephridia are 
developed. Furthermore, these organs lie in the ccelom, perforating the mesentery 
which separates the first from the second segment; hence Brereu’s objection to the 
homology between the larval and permanent nephridia, on the score that the former 
do not lie in the true coelom, is removed.” In the Platyheluunthes the excretory 
system has the form of a series of fine tubes formed of perforated cells, the terminal 
one of each branchlet being a flame cell. The latter may be wanting in the larval 
nephridia of other worms, though otherwise the structure of both sets is similar; and 
in others, again, where no free larval stage is present, the structures may still more 
lose their resemblance to one another. In Dinophilus also, which, according to 
Wetpon,* is “a form representing in its main features a stage in the evolution of 
Chetopods,” and possessing undoubted Turbellarian affinities, the excretory system 
resembles that of a Polychete larva. ‘The difficulties seem to lie in—(1) the presence 
of larval nephridia, which have, as Brrcu supposes, no connection with the adult 
nephridia ; (2) the structural resemblances between the adult nephridia of 
Platyhelmunthes, and the larval ones of Chetopods and Hirudinee. The question of 
connection with the cclom of the organs, supposed by Bzraxu to be homologous in 
the three latter groups, is not perhaps of such importance. In the first place, 
according to Brpparp, the larval nephridia of Oligochete, discovered by VEsDOVSKY, 
do open into the ecelom ; and beyond this it would scarcely be safe to conclude that 
structures present in Chetopods and Hirudinece, and evidently homologous in the 
adults of the two latter groups, were not homologous with structures in 
Platyhelminthes, simply because of the nature of the cavities into which they opened ; 
especially also taking into account the fact quoted by Bzpparp, that in Capitellidee 
the nephridia le within the mesoderm, and not in the ccelom, and that in Polygordius 
the greater part of the nephridium is similarly situated. As to the difficulties 
arising out of the fact that two sets of nephridia are present, it must be remembered, 
first of all, that, apart from Harscumr’s observations on Polygordius, WuitMaN states 
that there is a connection between the structures in Hirudinee. Further, it is a 
point of importance, as Brepparp points out, that these are always placed at the 
anterior end of the body, and so do not correspond in position with the nephridia of 
Platyhelmanthes. It is possible again that these simple larval nephridia are purely 
larval structures, not phylogenetically related to those of the adult forms of their 
ancestors; or that, again, they are portions of the adult nephridia precociously 
developed, just as portions of other structures are developed in the larve for use 
during larval stages, in either of which cases the great obstacles to comparing the 
adult nephridia of earth-worms and Platyhelminthes would be done away with. 
* Q.J.M.S. August 1886, p. 117, 
