. Carnegie Institution of Washington publication. . FIG. 17.— Ulothrix zonata.—(After Dodel-Port.) A, young plant. B, Zoosporangia, showing escape of swarm-spores. C, an asexual swarm-spore. D, gametangia, showing gametes and escape of same. E, two gametes. F, G, copulation of gametes. H, zygote. J, zygote after a period of rest. K, germinating zygote whose contents have divided into a number of swarm-spores. membranes. In the first division the granular plasma only is halved. The outer plasma membrane (Hautschicht) is undivided, and the membrane surrounding the vacuole remains unchanged. By f
. Carnegie Institution of Washington publication. . FIG. 17.— Ulothrix zonata.—(After Dodel-Port.) A, young plant. B, Zoosporangia, showing escape of swarm-spores. C, an asexual swarm-spore. D, gametangia, showing gametes and escape of same. E, two gametes. F, G, copulation of gametes. H, zygote. J, zygote after a period of rest. K, germinating zygote whose contents have divided into a number of swarm-spores. membranes. In the first division the granular plasma only is halved. The outer plasma membrane (Hautschicht) is undivided, and the membrane surrounding the vacuole remains unchanged. By further successive divisions these two protoplasts give rise ultimately to the gametes. The process of division is the same whether gametes or asexual swarm-spores result (Fig. 17, D). Strasburger has expressed the opinion that, in the development of the gametes, only one more cell-division is necessary above those required for the zoospores, and this division 1'enders the resulting cells or gametes incapable of further independent development. In what way this last division incapaci- tates the gametes for further independent development was not dis- cussed at the time. That view was probably prompted by Weismann's. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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