RELATION TO ONTOGENY AND PHYLOGENY IN ASTEROID, WITH PATICULAR REFERENCE OF THE MOST LIVING PRIMITIVE GENUS, LUIDIA

(1)本研究观察了斑Luidia maculata Muller et Troschel通过变态发育的过程。卵直径为173毫米。受精一个半小时后，卵裂为全卵裂，呈放射状。胚胎通过皱褶囊胚期发育成双胞体。受精后40天，双足后部逐渐发生蜕变。在这个阶段，出现了9个针状体，与成人骨骼的终板相对应。一周后，双羽蕨的长度达到2.5毫米。受精后64天，蜕变完成，产生的幼体直径约为700毫米。它们有9条手臂，每条手臂上有2对管脚。(2)本研究表明，本种的个体发育可能与鲁迪亚种的系统发育关系具有以下特征。1.本种发育为非腕肢动物类型，与以前报道的本属所有种相同。2. 目前的观察证实了Mortensen（1938）的观点，即双翅虫的形式和在属中的系统位置之间的相似性。因为本种属二进生生伞属（Doderlein 1920）的双翅足比属三进生生伞属的L. quinaria少一对双翅足。3. 多臂类小行星中，由于刚蜕变的幼星与成星一样有9条臂，其臂的形成时间与陆底亚种的分类学有关。

(1) In this study, the development of Luidia maculata Muller et Troschel, through metamorphosis was observed. The eggs are 173 mum in diameter. One and half hours after fertilization, cleavage is total and radial. Embryos develop into a bipinnaria through the wrinkled blastula stage. Metamorphosis takes place gradually at the posterior portion of the bipinnaria, 40 days after fertilization. At this stage 9 spicules, corresponding to the terminal plates of adult skeleton, appear. One week later, bipinnariae reach a length of 2.5 mm. Sixty-four days after fertilization, metamorphosis is completed and resulting juveniles are about 700 mum in diameter. They have 9 arms and bear 2 pairs of tube-feet in each arm.(2) This study shows the ontogeny of the present species may be correlated to the phylogenetic relationships of the species of Luidia in the following features. 1.Development of the present species is the non-brachiolarian types as all species of this genus previously reported. 2. The present observations comfirm Mortensen's view (1938) on the parallelism between the form of the bipinnaria, and the systematic position in the genus. Because bipinnaria of the present species belonging to the 2ndly advanced Alternata group (Doderlein 1920) has less one pair of bipinnaria arms than those of L. quinaria, which is included to the 3rdly advanced Quinaria group. 3. Because of just metamorphosed juvenile bearing 9 arms like the adults, the time of arms formation in multiarmed species of asteroid is related to the systematics of Luidia species.