524, FRANK E. BEDDARD. 
deferentia (p. 332: “‘ Hier finden sich beim jungen Tiere 
in den Genitalsegmenten aufangs nur Segmentalorgane, die 
mit der Entwickelung der Geschlechtsorgane degenerieren ”’). 
This is a matter that requires confirmation, since Bergh dis- 
tinctly states that there is no such degeneration. Jiehmann 
gives no figures of the development of these organs. The 
paper concludes with a brief summary of the arguments for 
and against the view that the genital ducts and nephridia are 
corresponding structures. The arguments against lose some 
of their weight by reason of the statement that no instance is 
known of the presence of numerous nephridia in a single 
segment in the Oligocheta (!). This paper was published two 
years after I found that Acanthodrilus multiporus is 
furnished with multiple nephridia, and communicated the dis- 
covery to the Royal Society. 
Dr. Benham, in discussing this question (5), also admits 
the probable homology, which he regards as fairly evident in 
the case of the oviduct. As to the sperm-duct, it is suggested 
that the modification which the nephridium has undergone 
is—(qa) a fusion of a series of nephridia, (d) a disappearance of 
a part of nephridia, (c) a shifting of the position of the pore. 
** In the somites in which the ciliated rosettes are, the external 
extremity of the nephridium has disappeared; in the somites 
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.” 
Professor W. B. Spencer (22) writes decidedly against any 
homology between genital ducts and nephridia. The first 
objection which he puts forward is the inter-cellular duct of 
the vasa deferentia and oviducts, and the intra-cellular duct 
of the nephridia. This objection would of course apply equally 
well to the homology between the nephridia of Oligocheta 
and those of many Polycheta; and, as a matter of fact, I show 
in this paper that an intra-cellular duct is, in the case of ovi- 
duct and vas deferens, actually converted into an intercellular 
duct. Another difficulty is “the presence of the perfectly 
