Observations on the Development, Structure and 

 Metamorphosis of Actinotrocha. 



By 

 Iwaji Ikeda, Bigahishi. 



Wlfh Plates .YA'T'-.YA'X. 



Introductory. 



Since tlie discovcrv of ActlnotrocJia hy Johannes Mulleiî 

 in 184'.), tliir^ peculiar larval form and its mother animal, 

 Phoronis, have been made the subject of investigations by many 

 distinguished authors such as Wagener ('47), Gegenbaur ('54^ 

 Krohn ('54), Schneider ('62), ]\[ETScnNiKOEF ('72, '82), E. 

 B. Wilson ('81), and Foettinger ('82). Among more recent 

 writers Caldwell ('85), INFc'Intosh ('88), BENTL\:\r ('88), 

 Roule ('90, '96), Cori ('91), and E. Schultze ('97) may be 

 mentioued as having published impoi-tant contributions ; whiU- 

 Masterman ('97) has ]nade quite an elaborate study of the 

 animal with the view of establishing its relationship to Balano- 

 fj/o.<i<in.s and the Chordata in general. As, however, in spite of all 

 these works there still existed many gaps and unsatisfactory points 



