REPRODUCTION IN ZONARIA FARLOWII. I. GAMETOGENESIS, SPOROGENESIS, AND EMBRYOLOGY1

Abstract

The brown alga Zonaria farlowii which exhibits an alternation of isomorphic generations has been found to be a particularly suitable organism for a comparative study of game to gene sis, sporogenesis, and embryonic development. The germinations of the zygote and spore have been compared and found to be similar. The development of the oogonium and sporangium has been studied with the light and electron microscopes, in an attempt to discern ontogcnetical similarities or differences. The timing and periodicity of oogenesis and sporogenesis were found to differ: oogonial development requires a lunar month from the time of its initiation to the time of egg release which occurs around the first quarter of the moon, whereas the sporangium does not follow this periodicity. The development of the spore embryos and zygotic embryos is essentially the same. It appears that the difference between the 2 phases of the life cycle exists only in the later stages of oogenesis and sporogenesis. These differences continue in the egg until fertilization, after which the zygote has the same cytoplasmic configuration as the spore. It is also notable that during release of the spore it must increase in size considerably since before germination begins it has attained the size of the egg.