. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 240 R. PHILLIPS DALES and preventing the sand from falling in around the anus while respiration is in progress. The general pattern of zonation is shown in Figure 6. The six stations were spaced at intervals of about 6 meters between high and low water marks. Samples were taken each month using a square frame with sides 25 cm. in length (enclosing an area of 625 or %<} ), the sample being passed through a sieve with round holes mm. in diameter. It will be seen (Fig. 6) that worms extend from low water mark to
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 240 R. PHILLIPS DALES and preventing the sand from falling in around the anus while respiration is in progress. The general pattern of zonation is shown in Figure 6. The six stations were spaced at intervals of about 6 meters between high and low water marks. Samples were taken each month using a square frame with sides 25 cm. in length (enclosing an area of 625 or %<} ), the sample being passed through a sieve with round holes mm. in diameter. It will be seen (Fig. 6) that worms extend from low water mark to almost high water mark of ordinary tides, and are not restricted to a relatively narrow belt as McConnaughy and Fox have stated. This belief was due to the restriction of the larger worms to the upper part of the shore, the popu- 10 u. 600 U o 04 500* 2001 100 U CD MHWM STATION NUMBERS MLWM FIGURE 6. Zonation of Thoracophclia mucronata at La Jolla. Filled circles = number; empty circles = length. lation being most dense just above mid-tide level, while the younger worms—which are usually overlooked in the sand owing to their transparency—are restricted al- most entirely to the lower part of the shore. A clear division is apparent between the size distribution of worms taken above the mid-tide level where a certain degree of drying out takes place at low tide, and below mid-tide level where the sand re- mains at or near saturation point (Fig. 7). Two explanations of this division are possible. The larvae may settle over the whole intertidal zone but those above mid- tide level either do not survive owing to the rise in temperature or drying out of the surface sand, or are carried down the beach by the surf. The larger worms are not washed out because of their greater size and weight and ability to burrow be-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these ill
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
