292 Origin of the Malpighian Tubules in the Arthropoda. 
are at first tubular in character and are lined by an epithe- 
lium identical with that of the intestine; as they get further 
away from their point of opening into the intestine these tubes 
lose their tubular character and become continuous with un- 
doubted nephridial tubules, with a duct excavated in the sub- 
stance of cells; the lumen, at first zntercellular, becomes 
afterwards zntracellular ; these tubules were absolutely undis- 
tinguishable from the nephridia, and, indeed, appeared to join 
the general nephridial network of their segment. Their lumen, 
which was here and there much swollen, contained a granular 
detritus identical with that occupying the tubes of the general 
nephridial network. These nephridial appendages of the proc- 
todeum are branched and anastomose one with another; they 
may certainly be compared to the anal nephridia of the 
Gephyrea. All that is necessary to convert these structures 
into Malpighian tubules is to limit their number and arrange 
them in aregular fashion; the branching and anastomosis even 
may be retained, as these conditions are met with among the 
Malpighian tubules of the Tracheata. 
If these inferences do not commend themselves to mor- 
phologists, I may at least point out that the above facts, of 
which I give here only a preliminary account, have some 
bearing upon the origin of the nephridia in Oligocheta. I 
have put forward an opinion that the original state of the 
nephridia in this group was a continuous network with nume- 
rous irregularly-disposed external pores and ccelomic funnels, 
such as is now largely persistent in certain species of Pert- 
cheta; and that Zumbricus, with its paired metameric 
nephridia, is the last term in the series which is partially 
filled up by intermediate conditions. ‘The connexion of the 
nephridia with the gut is probably secondary, as the orifices 
were originally external and were carried in by the involu- 
tion of epiblast to form the proctodeeum ; hence the polystomial 
condition of the nephridia is probably in ontogeny, as in phy- 
logeny, archaic. An analogous series of facts have been 
lately brought forward by Spencer, who found (“ The Ana- 
tomy of Megascolides australis &c.,” Trans. Roy. Soc. Vic- 
toria, vol. i. pt. 1) numerous nephridial openings into the 
anterior, probably stomodeal, part of the gut. I should 
refer these facts to the same category as my own, as evidence 
of the archaic nature of the diffuse condition of the nephridia, 
