. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RELATION BETWEEN SCATTERING LAYER AND EUPHAUSIACEA 203 perature but constant illumination changes over abruptly to one of constant tem- perature but increasing illumination. There is again a lag in the evening ascent, and here also the change at the commencement of ascent is more abrupt. The relation of these observations to what is known of zooplankton tropisms will not be discussed until more analyses have been made, but two points in particular may be referred to. The hysteresis between the curves for ascent and descent m
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. RELATION BETWEEN SCATTERING LAYER AND EUPHAUSIACEA 203 perature but constant illumination changes over abruptly to one of constant tem- perature but increasing illumination. There is again a lag in the evening ascent, and here also the change at the commencement of ascent is more abrupt. The relation of these observations to what is known of zooplankton tropisms will not be discussed until more analyses have been made, but two points in particular may be referred to. The hysteresis between the curves for ascent and descent means that the trace of the scattering layer movements will not be quite symmetrical about a midday axis. Also, the fact that the organisms are able to ascend and descend faster than to the iso-illumination curves means that the speed necessary to keep pace with changing illumination is well within the capacity of the animals concerned. Maximum recorded speeds are of the order of one to two fathoms per minute which does not seem excessive for as active an animal as a euphausid. Records from 18 <r 16 - 14 - 12- 10- 0540 DESCENT. 0430 1745 1200 — DAY FLATTENING - 18 o tc " 16- 15- 14 - '0550 ASCENT. 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woods Hole, Mass. : Marine Biological Laboratory
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
