CONTRIBUTIONS TO JAPANESE ASCIDIAN FAUNA -IX.RE-DESCRIPTIONS OF OKA'S SPECIES FOUND IN "FIGURARO DE JAPANAJ BESTOJ"-

A. OKA (1927) gave brief descriptions of a number of ascidian species in "Figuraro de Japanaj Bestoj" under new names, each with an explanatory note "(仮)" at the end. This note indicates that the name is given provisionally without full description nor sufficient consideration on the identification. Some of these species were redescribed or some names were replaced with known ones by 0KA himself, but eight species remain still untouched in the revised edition of the "Illustrated Encyclopedia of the Fauna of Japan" (1947); they are each marked with (MS) at the end of the name. I had chances to re-examine some type specimens or specimens identified by OKA himself and by this date I could give redescriptions of three species and found out that two are synonyms of the species already known to us. Here, the last three provisional species are redescribed each on the type specimen kept in the Zoological Institute of the Tokyo University of Education

ASCIDIANS COLLECTED BY MESSRS. RENZI WADA AND SEIZI WADA FROM THE PEARL-OYSTER BED IN THE ARAFURA SEA IN 1940

The present material consists of 27 species collected by Mr. RENZI WADA of the former Nan'yo Pearl Company and Mr. SEIZI WADA, an associate of the former Palao Tropical Biological Station, from the pearl-oyster bed off Melville in the Arafura Sea during the period from September to November of 1940. I express here my hearty thanks to Messrs. R. W ADA and S. W ADA for their kindness in offerring me the present precious material. I am also very grateful to Prof. T. KOMAI for his kind guidance and incessant encouragement. The present work is a part of the study progressed by the financial aid from the Ministry of Education

"Dynamic Optimality of Yield Curve Strategies"

This paper formulates and analyzes a dynamic optimization problem of bond portfolios within Markovian Heath-Jarrow-Morton term structure models. In particular, we investigate optimal yield curve strategies analytically and numerically, and provide theoretical justification for a typical strategy which is recommended in practice for an expected change in the shape of the yield curve. In the numerical analysis, we utilize a new technique based on the asymptotic expansion approach in order to increase efficiency in computation.