渦虫の1種Dendrocoelopsis lacteusの再生, とくに頭, 尾および咽頭の形成頻度

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The Present paper deals with the regenerative capacities of transverse pieces cut at 6 levels of the planarian, Dendrocoelopsis lacteus. The results obtained are summarized as follows: 1) In this species, there are two pairs of principal eyes. In many individuals, however, additional or supernumerary eyes are seen in the neighborhood of the principal eyes, as already pointed out by Ichikawa and Okugawa (1958). The number of supernumerary eyes is quite variable (Table 1). 2) A transverse section from any level of the body develops a normal head or abnormal head at the anterior cut end. The capacity for head formation decreases from anterior levels posteriorly, decreasing remarkably at levels posterior to the pharyngeal base (Fig. 1). 3) There are two types of eye-formation. In one type, during the early stages of regeneration a pair or eyes is formed with one eyespot each on the right and left sides of the anterior blastema. Then, slightly later the eyesports gradually are divided into two or more parts. In the other, a pair of eyes is formed as in the first type, and the other eyespots appear later separately by themselves. 4) The frequency of tail formation at the posterior cut end is nearly equal for each level, since tails were regenerated in more than 99 percent of the pieces. That is, no gradient in the frequency of tail formation was observed along the body axis. 5) The speed of pharynx-formation increases going from anterior levels towards the pharyngeal region. Sections from the postpharyngeal region regenerated a pharynx only when a head was also regenerated from the anterior surface of the section. In the latter case the speed of pharynx-formation is slower than that in pieces from the preoral region. The frequency curve for pharynx-formation exhibits a single peak which coincides with sections originating from the pharyngeal region, as is indicated in Fig. 1. 6) In section taken from the prepharyngeal region, pharynx-formation occurs within the old tissue situated medianly in tne posterior cut surface. While, in the case of piece from postpharyngeal region, it occurs medianly in the anterior end. The regenerated pharynx is located more posteriorly in more anterior pieces, and it becomes increasingly posterior in position the more time has elapsed since cutting the sections. In more posterior sections, the tissue regenerated from the anterior surfaces increases in length. The length of the tissue at the posterior surface gets shorter and shorter in the more posterior pieces. Finally, the regenerates attain the same length, and the sections from each level do not differ in their regenerated form, no matter what the level of their origin.
社団法人日本動物学会の論文
1964-09-15

渦虫の1種Dendrocoelopsis lacteusの再生, とくに頭, 尾および咽頭の形成頻度

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