(32) 



is ccr'-ect. As ytatca abov3, I consiuer tne pit to be of ec- 

 todennal origiu. (Fij:.24) Further stuay of the stn.ct'jre 

 leads me to agree with Ikeda that it divides into two lateral 

 branches each of which becomes a nephridial cai.al o^ the Ac- 

 tinotrocha. (Fit^a. 26-27-26-2.)) In Fig. 25, v;hich is a draw- 

 ing made from a living larva, the canals whicii in a little 

 younger stage were practically tr.e same aiameter throu^^hout 

 their length have becoruC tippea at tn ei r aistal ends wi tli a 

 bunch 0-^ cells v/hich, I believe, are later to form the excre- 

 tory cells of the nephridium. 



I am unable to maKe aiiy positive statement concerning the 

 origin of tiiese cells, since it is difficult to obtain many 

 larvae o "^' P. architecta which are old ciiough to show ti.ose 

 bunches of cells in ti^e process of formation. From all the 

 sections that 1 have examined I have not had any evidence that 

 they are fonriod by free mesoaerm cells attaching-, tijomselves 

 to tne internal ends of t ne nephridial canals ana I am rather 

 inclined to consider them as arising from the cells of the 

 internal blina ends of tne nephridial canals. (Figs. 25-28) 

 Ikeda's description (9) o f the way the nephridial tubes arise 

 from the cctodem^al pit; i. e. by tr.e "recvagination of the 

 distal luipal'-v^u ^.crti^n of the nephridial pit%b-ee.Tfc> 'lo me to 

 be correct. Lon^champs* ( 12) interpretation of ti;e chaiige in 



