(64) 



..all of the collar to form the v/all o 1' tne oral end of tiie tjut 

 seems to cause a ciiaijjje in the position of trie xiephriaial canals, 

 (See section on nephriaia) 



_ C avity of the Preoral Lobe;- Since tne precral lobe ia 

 lost durin,: txie metamorpnosi s, its cavity does not take part in 

 the yti'ijcture of the adult. 



Mesentery B etween the Lobe and Collar;- This mesentery 

 do es no t p ers i s t . 



Lar V al Co 1 1 ar Ca vi ty ; - As has been stated by other in- 



vestii-;ators arxl as I have observed the larval collar cavity 

 -.-.'ith its rnesodenr'.al wall becomes the rinj^ vesoel of the adult. 

 I shall discuss this or^^an further in the section on the vascu- 

 lar system, 



"Aault Collar C avit:/;-" (Ikeda) This cavity, v/hich is 

 founa in the well developed Ac tino t ro eiia, uijdoubtedly becomes 

 the "adult collar cavity" or supraseptal cavity of the adult, 

 as Ikeda has described. In the younj^ Phoronis, it is seen as 

 a cavity v-tiich occupies all tne region anterior to the trans- 

 verse septum and v-hich is prclongca into the t entac les, (Fig. ob) 

 It is lined by a mesodenrial epithelium ana it contains the ring 

 vessel with its tentacular vessel, 



-i^i:ilIiiL,Cavi_t:/ and Cavi ty of the Ventral Pouch:- Those cav- 

 ities become the-^ infraseptal cavity of the aault 



