. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 448 J. A. ADAMS. >SKhWER KNOT FIGURE 2. Diagram showing an animal that has been transected at the positions 1/H border and the positions Br/4 border followed by reversal of the gastric and budding regions (gbr-reversal) and threading of the graft pieces on a skewer of human hair. Two knots of human hair have been placed at either end of the graft pieces to insure apposition during healing. (artificial pond water, Loomis and Lenhoff, 1956) was changed approximately one hour after feeding to remove uningested nauplii. Exper
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 448 J. A. ADAMS. >SKhWER KNOT FIGURE 2. Diagram showing an animal that has been transected at the positions 1/H border and the positions Br/4 border followed by reversal of the gastric and budding regions (gbr-reversal) and threading of the graft pieces on a skewer of human hair. Two knots of human hair have been placed at either end of the graft pieces to insure apposition during healing. (artificial pond water, Loomis and Lenhoff, 1956) was changed approximately one hour after feeding to remove uningested nauplii. Experimental animals were kept in 15 mm X 60 mm Petri dishes, one animal per dish, to allow for individual observations of each animal and to prevent any chance of confusing 2° heads with retained buds. All animals used in this study had a single stage I bud (bud staging methods of Shostak et ai, 1968 were used). Grafting was performed by first making the appropriate transections and placing the graft pieces on straight skewers of human hair (Shostak, 1972). Pre-tied knots of human hair were loosened with watchmaker's forceps and placed on each end of the skewer. The knots were then tightened and slid along the skewer until all cut surfaces were touching (Fig. 2). Grafts were allowed to heal for two and one-half hours and were then removed from the skewer. Secondary head regeneration was monitored at 24 hour intervals for a period of four days. Any differences between the frequencies of 2° head regeneration in the groups of animals were tested using Chi square at a 95% confidence level. RESULTS AND DISCUSSION Regeneration of 2° heads at the distal end of position 1 is observed at 24, 48, 72, and 96 hours post-grafting. The resulting observations are shown in Table I. No 2° head regeneration is seen at 24 hours for either group of animals, thus 24 hour data are not shown. At 48 hours 18% of the animals in the g-reversal group have TABLE I Head regeneration in Hydra oligactis foll
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