138 E. S. Goodrich. 



out to a mere film of protoplasm; this finally breaks down allowing 

 a free passage to the genital products, as appears in flg. 12. Since 

 such thin partitions are sometimes found in fully grown specimens, 

 I am inclined to believe that they can be reformed after the genital 

 cells have passed through. 



The full-grown coelomostome of the female Asterope Candida 

 opens into the nephridial canal about half-way down its course; 

 bnt in the male the calomostome becomes immensely lenghtened, 

 Fig. 9, shows the nephromixium of a male: the coelomostome forms 

 a long tube or coelomoduct running parallel to the nephridial canal 

 and only opening into it near the nephridiopore. A small portion 

 of the two tubes is drown on a large scale in Fig. 10. 



Now this at once suggests a clue to the mode of origin of the 

 nephromixium in the Alciopids, and indeed in the Polychaeta in 

 general. 1 ) We may suppose that originally nephridium and coelo- 

 mostome opened independently to the exterior (Textfig. B 1), as is 

 still the case in the Capitellids. Then the two openings grew close 

 together, and finally joined. The two ducts now fused to a common 

 tube close to the pore (Fig. B3). Lastly the coelomostome opened 

 farther and farther up the nephridial canal until it came to open 

 almost directly into the anterior end of the nephridium, as in Alciope 

 cantrainii and in most Phyllodocds. A sort of economy of growth 

 appears to have taken place, where by the short coelomostome has 

 made increasing use of the nephridial canal to lead the genital 

 products to the exterior. 



Alciope also throws light on the origin of the type of nephro- 

 mixium found in Nephthys and Glycera.-) 



It will be remembered that in both these genera the closed 

 solenocyte-bearing nephridium is closely associated with a somewhat 

 funnel-shaped 'ciliated organ', the modified and reduced coelomostome. 

 The genital cells appear no longer to escape to the exterior by 

 their natural path, the coelomic duct, but by bursting through the 

 body-wall. This is almost certainly the case in Nephthys, and most 

 probably also in Glycerids. But the coelomostome has taken on 

 another function, that of accumulating excretory products (mostly 

 collected by floating amoebocytes) in the neighbourhood of the 



1) Goodrich, 1. c. 



2) Goodrich, Od the Nephridia of the Polychaeta, Parts 1 and 2, 

 in: Quart. Journ. Micr. Sc, Vol. 40, 1897; Vol. 41, 1898. 



