| Summary: | P(論文) The results of the investigation on the variation of the 10 taxon of the diatoms are reported in the sections 2-11 in detail. This is the summary. Form of shells is classified into 3 taxon such as those which vary strongly, those which do not vary so strongly, and those which scarcely vary. The taxon which strongly varied were Achnanthes brevipes var. arctica, Achnanthes lanceolata var. lanceolata f. dubia, Cymbella cistula, Hantzschia amphioxys var. recta, Navicula muticopsis var. muticopsis f. capitata, N. m. var. m. f. murrayi, etc. The taxon which were not so varied were Achnanthes brevipes var. intermedia, Pinnularia subcapitata var. subcapitata, etc. The taxon scarcely varied was Navicula cryptocephala and N. molesta. However, this Navicula cryptocephala was varied strongly at the central striae which were long and short alternately or not alternately, although not so strong variation was observed in the outer shape of shells. Thus, variation is sometimes very strong on a certain characteristic, but scarcely found on the other characteristics. And sometimes variation is not found on all the characteristics at a time. For example, Cymbella cistula which was collected from Oze situated in the central part of Japan was not so varied in shell shape, but the same species that was collected from South Georgia of the Antarctic strongly varied in shell shape. It seems from this fact that according to the difference of the growing circumstances or strains, even the same species strongly vary in some cases, and may not vary so strongly in other. Therefore, the writer thinks that it is not enough to examine the materials from only one place in order to study variation. However, in order to assertain the characteristics for standards of classification, like the purpose of this work or to re-arrange the taxon which are classified into many species on the basis of the variable materials at a place, the writer has found that the study of the materials collected from a particular place is fairly effective. The ...
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