528 FRANK E. BEDDARD. 
Lumbricus; the converse supposition is incredible, although 
the development appears to be so different. In Lumbricus 
the pronephridia become the persistent nephridia after but 
little change; there is no “‘ flame-cell,”’ as in Rhynchelmis 
(Vejdovsky); in Acanthodrilus multiporus the pro- 
nephridia are converted into the nephridia by the degeneration 
of the funnel and by the multiplication of the external pores ; 
it is after this has occurred that the genital ducts are split off. 
I can only reconcile this mode of development with that shown 
in Lumbricus by the supposition that the persistent nephridia 
in that type are not the exact equivalents of the paired 
nephridia of the young Acanthodrilus, but that the break- 
ing up of the nephridium is slurred over, only showing traces 
of its former existence in the funnels and the proximal portion 
of the genital ducts. In this case the apparent simplicity of 
the nephridia in Lumbricus, and their apparent corre- 
spondence with an early stage in the development of the 
nephridia of Acanthodrilus will be delusive. If, on the 
other hand, it be proved that the nephridia of Lumbricus 
have never advanced beyond the stage which characterises the 
embryo Acanthodrilus, some explanation will have to be 
offered of the different modes of development of the genital 
ducts in the two types. 
The whole matter is evidently not ripe for solution at present, 
and the problems involved grow more difficult as fresh facts 
are accumulated. 
§ Remarks upon the Nephridia in the Oligocheta. 
The facts recorded in this paper have an obvious bearing 
upon the question of the evolution of the excretory organs in 
the Oligocheta. But before discussing how far these facts 
affect current theories upon the matter, it will be useful to 
clear the ground by briefly describing the structure and 
development of the nephridia in other Oligocheta. 
Lumbricus and Allolobophora.—We owe our know- 
ledge of the development of the excretory system in these types 
principally to Kleinenberg (24), Vejdovsky (1, 2), Bergh (12), 
