MKPHJIIDIA OF THE AOTINOTROUl-l A LARVA. 117 



The large canals remain as the paired nephridia of 

 the adult." 



De Selys Longchamps is also of the opinion that the canal 

 of the larval nephridia persists as that of the adult organs, and 

 that " ces canaux acquierent secondairement chacun un oinfice 

 en entonnoir qui debouche dans la cavite posterieure du 

 corps." Menon likewise states that the larval " nephridia 

 become the nephridia of the adult Phoronis," and Ikeda 

 comes to much the same conclusion. 



In just-metamorphosed larvas from Faro I find the canal of 

 the larval nephridium occupying just the same position on 

 each side of the anus as the excretory ducts of the adult, and 

 showing no signs of degeneration (fig. o). The inner blind 

 end still lies in the pre-septal haemocoel (lophophoral ring- 

 vessel), but, as Caldwell observed, the solenocytes have dis- 

 appeared. Their remnants are possibly to be found in certain 

 small deeply-staining nuclei floating in the blood. No trace 

 whatever can be seen of an opening into the coelom at this 

 stage, and I am strongly of the opinion that the coelomic fun- 

 nels are later developed from the coelomic epithelium, as was 

 suggested by de Selys Longchamps, and become subsequently 

 grafted on to the nephridial canal. This is one of those im- 

 portant gaps in the history of these organs which still remains 

 to be filled up. 



If future observations show that the adult organ is made 

 up of the nephridial canal of the larva to which a coelomostome 

 becomes added after the metamorphosis, the structure of the 

 adult excretory organ of Phoronis would be wonderfully like 

 that of the compound " nephromixia " I have described in 

 certain Polychtete worms — more especially like those of the 

 Phyllodocida? (6). 



Summary and Conclusion. 



It has been shown above that in the Actinotrocha larva 

 there is one coinplete septum separating a closed posterior 

 trunk coelom from an anterior pre-septal heemocoel, which ex- 



