(116) 

 of the mesodermal lininj-: of the stomach. The aorsal vessel be- 

 comes the afferent vessel of the adult while the efferent vessel 

 does not arise until just after metamorphosis, Tne collar cav- 

 ity, vvhicri is a part o ■f' tne blasto coel, becomes the ring vessels 

 and tentacular vessels of the adult. There is no connection 

 between the dorsal blood vessel and Masterman's "subneural sinus' 



The blood corpuscles arise from the somatic mesodenrial lin- 

 ing, of the ventro-lateral collar wall just in front of the sep- 

 tum. They make their ap-^earance as tv/o masses of cells bilat- 

 erally placed, one on each side of the median ventral line and 

 as ihe-j develop, they migrate across the collar cavity and be- 

 come applied to the naked walls of the stomach. 



The rudiment of the supraseptal or collar cavity of the 

 adult makes its appearance in about the same rej^ion as do the 

 blood corpuscles but a little later in the life history of the 

 Actinotrocha, 



During metamorphosis, the follomng organs are lost: the 

 preoral lobe, the gai^glion and the larval tentacles. The ec- 

 todermal wall o^ the collar cavity, the stomach diverticula, the 

 digestive areas and the perianal ciliated ring are not destroyed 

 but they lose their identity. The subepidermal nervous layer 

 of the trunk aiid ventral pouch becomes part o<^ the same tissue 

 in the adult but- the larger part of this tissue, as well as the 



