ON A NEW ORGAN IN THE LYCOEIDEA. 393 



nephridial canal, owing to their size; but their nuclei alone 

 could not pass down its tortuous and narrow lumen. The 

 genital products must therefore escape either by dehiscence, 

 as held by Mr. Cunningham (4), or by means of genital ducts 

 (ducts such as we know to be formed at maturity in the 

 Nemertines) .^ The former method would be neither agreeable 

 nor advantageous to the parent ; the latter, on the contrary, 

 would seem to be the natural one. 



The fact that no dorsal organs were found in the two 

 Heteronereids I have examined, does not appear unnatural 

 when we consider that these forms are much modified for 

 the purpose of dispersing the ova, and are in many respects 

 degenerate and unfitted for a long life.^ Probably, in this 

 case, dehiscence takes place, followed by the death of the 

 individual. 



The Nephridia. 



Although many naturalists have examined the nephridia of 

 various members of the family Lycoridea, these organs are still 

 but incompletely known. 



One of the chief difficulties we meet with in studying the 

 nephridia of the Nereids, is owing to the small size of most of 

 these worms (except Alitta virens and Nereis pelagica, 

 which unfortunately 1 have not been able to obtain alive). 

 However, if a N. di versicolor be carefully dissected under a 

 powerful lens, the nephridia may sometimes be seen as small 

 yellowish or whitish bodies at the base of each parapodium. 

 On removing these with the septa, the whole organ, both body 

 and funnel, may occasionally be obtained. It is then seen to 

 consist, as described by Mr. Cunningham (4), of an opaque, 

 massive body, containing a convoluted tube, which leads to a 

 long canal terminating by a small funnel, the internal opening. 



' Should future observations establish the fact that the dorsal ciliated organ 

 is a genital duct, it might well be compared with the metameric genital canals 

 of the Nemertines. 



^ Not only is the alimentary canal much reduced (according to Claparede [2] 

 the Heteronereids take no food), but the nephridia also seem to be degenerate 

 and in some cases even absent. I have not, however, yet been able to examine 

 sufficient material to say anything definite on this latter point. 



VOL. XXXIV, PART IV. NEW SEE. D D 



