. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 286 FRANK A. BROWN, JR. but with apparatus directed in each of eight compass directions. A single observer on any given day would arbitrarily select one of the compass directions. Otherwise the observations were made just as in the first experimental series. All observers contributed to data from each compass direction. The observers were now in- formed, however, as to the experimental conditions obtaining, but four of the five observers were uninformed of previous work, or even of the nature of the problem. The results of t
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 286 FRANK A. BROWN, JR. but with apparatus directed in each of eight compass directions. A single observer on any given day would arbitrarily select one of the compass directions. Otherwise the observations were made just as in the first experimental series. All observers contributed to data from each compass direction. The observers were now in- formed, however, as to the experimental conditions obtaining, but four of the five observers were uninformed of previous work, or even of the nature of the problem. The results of the four-month study are summarized in Table I, and the frequency distribution for each compass direction illustrated in Figure 3. There was reasonably good confirmation of the earlier South-directed "un- informed" experimental series. However, a clear compass-direction effect was now evident. When the apparatus was southerly directed, the increase in potential gradient turned the worms clockwise, when northerly directed, counterclockwise, with graded differences between these directions. More particularly (see Figure 4), the results suggested that the axis of the compass-direction effect was a S-SE to X-XW one instead of a magnetic X-S one. Relationship of response to time of day: While this last experimental study was under way data were being gathered from occasional comparable series run between 2 and 6 , commencing on September 15, 1961. These provided a strong •HO0 O O o _1 oo O o o ° cc Q h Z 0 o +5 o . • °% ' % • °. S°o°S °» . oo- o °^on °o °°° o o ° coo ° 0 o § ^ LJ cr o°0 ° °°°° !°° 0°oo°o° 0 00 0 ° 0 °00°0 00 o. o 0°° 0 o I 0 ° o o ° 00 00 H o < a -5° o o "o o z 0 < o u 2-,o° o -,5- 0 1 1 1 1 1 1 30 10 20 30 10 SEPT. OCT. 10 20 FREQ. FIGURE 2. The differences between path of worm samples (15 paths) in a 2-volt/cm. right-angle gradient and path in the same experimental series in an equipotential fi
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