(35) 



form of the "ectoaermal pit" a^^rees q^uto clooely -.vitii Ikeaa's 



descrii tion, 



_ "Medullary Plate", J Ro u le ) 



When the youii;,^ larva of Pnoronis a^chitecta nas reaciied 

 the tvv'o tentacle stae,e, cro^y sectiono csiio-: ti.at 'Ci.ere io a aef- 

 inite ve..tral ciliatea bam extenaiUf^ from the moutti to the cil- 

 iatea tentacular band. ("Pigs . 29 ( b) - (c ) - (a) - ( e) ) Tiii^^ ven- 

 tral ciliatea bana has been observed by Roule (20) in the larva 

 of P. Sabs.tieri but it has not been aescrihed for any other spe- 

 cies. Roule has hcmolot;izea it with the i;ieaullai"y plate or 

 medullary i^roove of the annoliu larva, 



Lon;,:c]-;amps has drav/n attention to a -^i^^ure of an Actino- 



trcchia published in Hatschek's "Lehrbuch ae r ZoolOi.ie". In 



this fit^;u.re are represented two coelomic sacs surroundinf: the 



intestine, Katschck docs not dose: be the orij^in of these su.cs 



but Lon^champs (pa^-e 555) proposes the question, "si les canaux 



a 

 ne deriy^ient pas des expansions lat o'^-i.j.:^ av dive-^ticulc ccto- 



blastique, chacun dcs canaux restant en rapport avec I'exteV- 



ieur par un orifice re'sultant du dedoubloment ae l»orifice ^Hm- 



itif et median, tandis que le restant au aiverticule ectcblas- 



tique deviendrait la cavite posteVieure du corps," 



Suchaii origin for this posterior cavity would seeiL to be 



a possible one and^woula t.;ive an easy explanation for the ori.in 



