Avian taxonomy of 'Linnean species' category had nearly been finished by 1940, 'New systematics' was proposed in 1940 by leadership of J. Huxley, and great contributions have been made by Dobzhansky, '37, Mayr, '42 and many others. The species problem was now attacked genetically and biologically, and therefore the 'biological species' concept arose. In Japan, Yamashina advanced cytogenetic method of classification based on hybrid sterility and chromosome caryotype (by means of special technique devised in Japan) and gave definitions to each category of classification from this basis.
The recent concept of taxonomy and species problem developed in two ways: one towards more and more molecular, or biochemical, analysis, such as egg protein (Sibley) and blood serem (Irwin, Mainardi) and the other towards more comprehensive analysis. The latter comprises two categories; first the structural-functional analysis with special consideration on the adaptive radiatiod among related species, the second being eco-sociological analysis in population level, which Mayr calls the 'population systematics', and Tokuda names it the 'dynamic concept' of species.
It can be said that the more conservative and inner is the character, the older phylogenetic affinity could be suggested. But, if the more variable and outer characters with direct influence of environment were neglected, we fail to realize the history of adaptive differentiation of a bird as a whole, because such innermost characters as egg proteins, blood serum, or chromosomes, are conservative to such extent that they are invariable even in ontogeny, which reflects some historic pattern of speciation. It was also pointed out that in such cases as sibling or occulto (Yamashina) species, the slight internal or genetic change has not yet influenced the external characters which remain unchanged conservatively. The population level concept sees the birds' society as unit and classify their species-specific types of life in the ecological system taking in consideration every biological characters; therfore it is the most comprehensive concept of species.
The ornithology has now become very complex, comprising many fields and data from each field, morphological, physiological, ecological and ethological, can be some contributions to taxonomy, and the species is a 'mozaic whole' of characters. The author is of the opinion that the species concept should be comprehensive and biological. But, data from various fields, which are being accumulated, are still too fragmental for a definite complex definition of species. Everything, living organisms, science, and industry, etc., evolve through the 'complication' and 'intensification' into the final stage of complex totality.
As to subspecies, it was added among others, that 'subspecies-group' should be expressed in birds' latin names in parenthesis after the species name, and the need of bio-ecological study of subspecies is commented.
This paper is dedicated to Dr. Y. Yamashina, the Director, who has made a great contribution to this problem, for his year of the 60th birthday.
