| Research Abstract |
The purpose of this research is to appraise the morphological variation of microfossils, including foraminifers, ostracodes and diatoms, in time and space, as well as to clarify the vicissitudes of microfossils through Cenozoic time. In 1988, we installed an image processor recently improved, and then have been engaged in selecting parameters suitable for measuring and setting off the morphological variations of microfossils among and within species in each of the above groups. Among pieces of our work accomplished since the second year are the following, although recent progress in our research will be contained in the collected papers, running into 60 pages, annexed to "the report on the results of our research" : Diatoms- Denticulopsis, a biostratigraphically important genus, includes several species which are difficult to be assigned to one or the others. This calls for biometrically laying foundations valid for their classification. In consequence, the length and width were measured, together with counting chambers, of each of the bands. The results show that with respect to D. lauta, the majority of bands have odd numbers of chambers, with a maximum number of 3 or 5 ; the existence of three types as to the arrangement of apical pseudosepta appearing at the ends of a band ; greater importance of chamber numbers and apical pseudosepta in analyzing their life cycles ; positive correlations between the length of and chamber numbers on bands, which indicate the possibility that the cell division gives rise not only to a reduction in the length of bands, but also to the modifications of their structures. Ostracodes- The regional extinction of stracode species due to a vicariance event caused by sea level fluctuations during the Pleistocene might involve ecological constraints which seem to be reflected on their dwarf carapaces, as exemplified by Sinocytheridea latiovata.
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