(9^) 



As Ikeda has pointed out, the efferent vessel of the adult 

 corresponds to the ventral vessel which. Mastenrian (15) and Roule 

 (20) have found in the Acti no trochae before raetano rphosis. 



In all the completely metarno rp hosed Ac tino trochae that 1 

 have sectioned there is but one rinc vessel, but th.e younc Pho- 

 ronis wiien it is twelve hours old, posses both the recipient 

 and distributing vessels; these vessels, 1 believe, arise from 

 the single ring vessel of the atetacio rphosin^ Actinotrocha by the 

 ■^usion of its walls aiid by the subsequent separation o f the tv/o 

 parts alonj^ tn^ line of fusion. 



Masterman in his description of the blood system of the 

 Actinotrocha speaks of a "rinc sinus" at the anterior end of the 

 intestine wliich connects the dorsal and ventral vessels. He also 

 says that there are two lateral branches of the dorsal vessel 

 in the rej;ion of the pharynx which pass dov/nwara arouna the oe- 

 sopha^'us ("post-oral rJn{,- sinus") and become continuous with the 

 ventral vessel. 



The former undoubtedly represents the sinus surroundiu^ th.e 

 loop of the alimentary caaial in the younj^ Phoronis, \\hile the 

 latter, 1 believe, represents the branches of the efferent ves- 

 sel v/hich become part of ti:e recipient vessel of the adult. 

 Masterman says that these branches open into the uorsal clood 



