(86) 



Jlerhridia :-,,,,^ Calciwell (5), Ikeda (9), Loi'it,charr.p3 (12) anu 

 Merion (17) have all observed the chaise in podition of x.ue lar- 

 val nephridial canals whicn id due to the chaises taicini^ place 

 during the critical periou o '' the me tamo rp ho sis ana it ij b.. 



Mite well eotablishea fact that the exten.al enas of the larval 

 .^ephridial canald ccmo to be situated near the anal openiiit.. 

 (7i;:.59) 



Just after the critical period, a cross section t.hroutrn the 

 aiiterior end of the youni Phoronis ci-its the transverse septum 

 ( "diaphraj^m" , "collar tnuiK mesentery") which runs oblini'^ely ana 

 passes throuj/n the ST'praseptal and infraseptal cavities. It 

 shows a transverse section tiirough the nephridial canals //hich 

 ,u,re still attached to the mesente»-y as in the Acti no t rocha. ^''cl- 

 lo-."Jni_, tho sections anteriorly, the canals are seen to open into 

 tne uupraseptal cavity ("larval collar cavities", "ring ves; sgI 

 cl tne aault") ax^a tn'^v j^r^ totill -f'ound in possession o ^' their 

 excretory cells. Posteriori:^ t.he sections shjov; th.at the ne- 

 phridial canals leave the septum and pass between tl;o wall and 

 the mesodermal lininj.; of the infraseptal cavity. (Fiji. 59) At 

 this time, their exten.al openings are situated on the lateral 



;:iaf^rr-:al wall in a trars verse plane which is somewhat below the 

 transverse plane of the anus and they are by no means as near to 

 liie latter as they are in the adult Phoronis. It is seen from 



