. Animal growth and development. Embryology; Growth; Biology; Growth; Embryology; Animals -- growth & development. The Life Cycle of the Single Cell 19 For example, if a growing culture of Gonyanlax is exposed alter- nately to 12-hour periods of light and dark (, a regular day-night cycle), cell division is confined to a very short time just before the end of the dark period. Thus the population increases like a staircase rather than steadily and continuously with time as do most microbial cultures. If now the culture is placed in constant dim light or total darkness, the population co
. Animal growth and development. Embryology; Growth; Biology; Growth; Embryology; Animals -- growth & development. The Life Cycle of the Single Cell 19 For example, if a growing culture of Gonyanlax is exposed alter- nately to 12-hour periods of light and dark (, a regular day-night cycle), cell division is confined to a very short time just before the end of the dark period. Thus the population increases like a staircase rather than steadily and continuously with time as do most microbial cultures. If now the culture is placed in constant dim light or total darkness, the population continues to mark off 24-hour cycles of rhythmic cell division. Thus the rhythm is persistent even though light, temperature, and other environmental conditions may be constant. (See Fig. 8.) The same was found to be true of its luminescence. A culture of Gonyaulax was incubated during alternating 12-hour periods of light and dark. At frequent intervals, measurements were made of the intensity at which the cells luminesced, with an instrument somewhat like an ordinary Fig. 8. Rhythmic cell division in Gonyau- lax. The upper graph shows the growth curve of Gonyaulax as a staircase rather than as a continuous line, because the cells do not divide at all times of the day and night but only during a short period just before "; The lower graph shows that even when the organisms are removed from the ordinary day- night cycle and placed in constant dim light, the 24- hour rhythm of cell division persists. 2, 3000 Period of cell growth Period of cell growth. ^ Light Constont dim light ne in hours. 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 Sussman, Maurice. Englewood Cliffs, N. J. , Prentice-Hall
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