(CO) 

 Huaiaieiit of tho "AcJulA ,CQ-lXar-Jlg:Vil^-- (Ii<eaa) Ike da has 

 observoo a- nieso dermal cell mass on the ventral somatic wall just 

 under the second tentacle in rather yount^ speciuiens of all tt.e 

 Japanese Actinot ro chae. He has traced the developaient of ttiis 

 mass of cells and finds that a cavity arises in it which, before 

 metamorphosis, becomes .^ui t<^ spacious aiid extends into the ten- 

 tacles. 1 aia a^ble to confirm Ikeda's vjev; tnat this cavity is 

 the rudiment of the "adi?lt collLtr cavity" or "suprasei-tal cavity' 

 o "^ the o.dult as it is usually called. (Pigs, ■30-4L-ol(h)-'iu (b) - 

 46 ) 



Metamorpho sis, 



Several inves tij-ato rs have carefully describea the external 

 characteristics o "f^ the me taiiiD rphosis of the Actinotrocha so it 

 \ is unnecessary Tor me to enter into a aetailed description , 



V/il3on(24) studied the metamorphosis of Ac tinotroc r.ae Spe- 

 cies, A. and Species, E. , which are founa in ChesaiieaKo Bay but 

 he did not cut sections of his material. 



