. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SPAWNING IN HYDRACTINIA AND PENNARIA 335 Eggs from each different batch were funneled into a standing column in a burette to measure their volume, and a rough estimate of their num- ber was calculated from counts of samples of known volume. Each batch produced well over 6,000 eggs on each day. Batch B was slightly more productive than batch A in the sum of its two sheddings the first day, but there was no significant difference the second day. It is clear that from 12 to 80 seconds of strong daylight is sufficient stimulus t
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SPAWNING IN HYDRACTINIA AND PENNARIA 335 Eggs from each different batch were funneled into a standing column in a burette to measure their volume, and a rough estimate of their num- ber was calculated from counts of samples of known volume. Each batch produced well over 6,000 eggs on each day. Batch B was slightly more productive than batch A in the sum of its two sheddings the first day, but there was no significant difference the second day. It is clear that from 12 to 80 seconds of strong daylight is sufficient stimulus to bring about a heavy shedding of dark-prepared eggs, and that illumination in excess of this is able to bring about the discharge of only a scattering few more eggs. It is not at all essential that the colonies remain in the light during the period from their re-illumination until the time they are shed. However, a very brief period of illumination depends for its effective- ness on an ample period of previous darkness. On July 18, 50 female colonies which had been continuously illuminated for over 24 hours were stored in the dark for one hour, exposed then to ten seconds of light from a 100-watt bulb two feet away, and then kept in the dark for 2% hours. No eggs whatever were shed, but after standing for an hour longer under the light bulb, a heavy spawn resulted. On the fol- lowing day, 34 of these same colonies, after 13 hours of illumination, were given an hour in the dark, ten seconds of daylight (north window, midday), and 1% hours in the dark. On removal to daylight again, a moderate shedding of eggs was found, but within the hour twice as many more eggs were shed as a result of the new illumination. No explana- tion can be offered why a procedure closely similar to that which failed to cause shedding the first day should succeed the following day. But in both cases it is clear that ten seconds of light, which would have been sufficient to precipitate a near-maximum she
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
