JOUENAL OF THE COLLEGE OF SOENOE, TOKYO IMPERIAL UNIVERSITY. 



VOL. XXXII., ABTICLE 12 



On Cyathocormus mirabilis nov. gen., nov. sp., 



the Type of a New Family of Compound 



Ascidians from Japan. 



By 

 Dr. Asajiro Oka. 



With 3 Plates and 6 Text-figures. 



Although the Ascidiae Salpaeformes or Luciae have all along 

 been regarded as a subdivision of the Order Ascidiacea, the 

 difference between the free swimming Pyrosoma and an ordinary- 

 fixed compound ascidian is certainly very striking. No form has 

 as yet been made known which might be considered intermediate 

 between these two groups. Even the curious unattached colony, 

 Coelocormus huxleiji, which w^as believed by Prof. Herdman to be 

 a transition form between them, has in reality nothing in common 

 with Pyrosoma beyond the tubular shape of the colony. On the 

 other hand, there are some recent investigators who regard 

 Pyrosoma as more closely related to Salpa and Doliolum than to the 

 ascidians. Neumann ('09), for instance, in Beonn' s Klassen und 

 Ordnungen des Tierreichs, has transferred the family Pyrosomidae 

 to the Thaliacea in which it constitutes the group Synthaliacea ; 

 and Paeker and Haswell ('97 & '10), in their excellent text- 

 book, have also adopted a similar view. 



The new genus of compound ascidians described in the 

 present paper is quite unique in combining the characters of the 

 compound ascidians and the Ascidiae Salpaeformes. In shape and 

 general appearance of the colony it very much resembles the 

 latter, while it agrees with some of the former in the possession of 



