Abstract
Some new knowledges concerned with reproduction and reproductive cells of a freshwater alga, Chaetonaarpha Okamurai Ueda are summarized as follows:1) The structure of fertile filaments of the present alga is described.2) Developmental processes of liberation pore formation are observed. Inner layer of cellwall firstly opens and later opens outer layer. Shedding out processes of swarmers are also described.3) Shapes and structure of gametes and zoospores are described and their dimensions are measured too.4) Sexual fusion takes its place not only among those gametes which are ejected from different filaments as commonly encountered as in most of algae, but also among those gametes ejected from a single filament. Moreoverr sometimes even among those gametes which are produced in a same game-tangium of a single filament sexual fusions are observed.5) Several types concerned with gamete fusions are enumerated: i. Anterior with anterior, ii. Anterior with ventral, iii. Posterior with pos-terior, iv. Posterior with anterior and v. Random-touching.6) Zygotes always become planozygotes and their motility never be weakened for a comparatively long time.7) In early autumn gametes often stand still and grow to become sporings parthenogenetically.8) The present alga is perennial and her method of reproduction is mainly by means of gamete formation through a year only excepting for by means of zoospores in early May and in early September.9) Phototaxis of swarmers of the present alga is differently characterized by each swarmer, namely positive by gametes and negative by zoospores, planozygotes and parthenogametes.10) Zygotes, zoospores and parthenogametes were cultured. The germination type of these three sorts of reproductive cells all belong to Inoh's “Immediate Filamentous Type” After 54 days' culture of zygotes and zoospores, their sporings grew to reach up to 665μ in length being composed of two to five much elongated cells.
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