Abstract
WHILE occupied with field-work on Siphonophora, I placed six small Pleurobrachia sp. measuring about 2.5 mm. in length in a watch-glass at 1100 hr. on April 29. An hour later I noticed that eggs were being extruded through the ectoderm over the gastrovascular canals. Since the fertilization membrane was present as the eggs were being extruded, it would appear that fertilization took place inside the meridional canals. By 1430 hr. the first and second cleavages of the majority of the eggs were taking place as in Beroe. By 1830 hr. the numerous micromeres were covering the macromeres by epiboly and many of the larvæ had reached the stage of gastrulation. Within twenty-four hours of extrusion the larval ctene-plates could be seen beating within the egg envelope. The same phenomenon was witnessed with another batch of Pleurobrachia on May 7, when less than half the eggs segmented.
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TOTTON, A. Egg-laying in Ctenophora. Nature 174, 360 (1954). https://doi.org/10.1038/174360a0
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DOI: https://doi.org/10.1038/174360a0
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