ON THE DEVELOPMENT OF THE SEA-STAR, ASTROPECTEN LATESPINOSUS MEISSNER

¹ Department of Biology, Toyama University, Toyama 930, Japan

1. The entire process of development in the sea-star, Astropecten latespinosus, is reported, especially with regard here to the external morphology and the skeletal system.

2. The eggs are medium-sized, about 300 µ in diameter. They develop into free-swimming larvae through a wrinkled blastula stage by holoblastic, radial cleavage.

3. The free-swimming larva has a peculiar barrel shape, being neither bipinnaria nor brachiolaria. Such a larva has not previously been reported.

4. Metamorphosis takes place while the larva is pelagic, and there is no feeding at this stage. Five days after insemination, metamorphosis is completed and the resulting juveniles bear 2 pairs of tube-feet and a terminal tentacle in each arm.

5. The present observations are compared with those studied by other workers, and are discussed, with special reference to the type of development of sea-stars.

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