THE NEPHRIDIA OF THE POLYCHJJTA. 709 



over various genera and species (Haplosyllis spongicola, 

 Gr., Autolytus, Myriauida^ Trypanosyllis^ Pionosyllis, Syllis, 

 etc.), were made on fresh and preserved material chiefly 

 obtained at Naples and Plymouth. 



Since much has already been written on the nephridia of 

 these worms by Ehlers (6), Saint Joseph (23), Claparede (2), 

 Malaquin (21), and others, it will only be necessary to dwell 

 in detail on certain points which seem to me not to have been 

 thoroughly elucidated. 



In the immature Syllids the nephridium consists of a 

 slender tube opening externally on the ventral surface, and 

 internally into the coclom of the next segment in front by 

 means of a simple nephrostome. It is generally stated that, 

 at the time of sexual maturity, the nephridium becomes much 

 enlarged, and serves as a genital duct. Ehlers, in his im- 

 portant work on the Polychgeta (6), says that " diese Organe 

 (segmental organsj sind in zustande der Ruhe ausserst feine, 

 innen wimpernde Rohren mit einer unter der Basis der Fiiss- 

 hocker gelegenen ausseren, und einer in Mitte des Segmentes 

 miiudenden inuerer Oifnung. Zur Brunstzeit entwickeln sich 

 die Oi'gane zu sackartigen Behalten, welche durch aufnahme 

 der Geschlechtsproducte durch die innere Oft'nung bis zur 

 ganzlichen Anfiilluug des Segmentalraumes ausgedehnt 

 werden. Die Eutleerung der Eier und des Samens erfolgt 

 durch die aussere Offnung des Segmentalorganes " (p. 215). 

 Malaquin, in his 'Monograph of the Syllids' (21), goes a 

 little further into detail : — " La nephridie reduite pendant une 

 grande partie de la vie du Syllidien a un canal etroit, simple- 

 ment courbe en arc et a trajet horizontal presente, a Fap- 

 proche de la maturite sexuelle, c'est a dire au moment oii les 

 produits des glandes genitales commencent a remplir la 

 cavite geuerale, un accroissement secondaire qui se manifeste 

 tout d'abord par une dilatation du canal nephridien ; puis par 

 une croissance longitudinale ce qui necessite un reploiement 

 de la nephridie sur elle-meme. . . . L'entonnoir vibratile lui- 

 meme s'elai-git de fa9on a laisser peuetrer facilement les 

 spermatozoides " (p. 280). 



