292 Orngin of the MalpigMan 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 inferceWular, becomes 

 afterwards z'/?^racellular ; 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- 

 todaium 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 a regular fashion ; the branching and anastomosis even 

 may be retained, as these conditions are met with among the 

 Malpighian tubufes 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 Oligochaeta. 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 Peri- 

 chceta ; and that Lumbricus, 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 proctodeum ; 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 stomodajal, 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. 



