Abstract
A study has been made of the effect of near infra-red radiation on the subsequent fertilization of the eggs of some marine invertebrates. The species studied were 2 sea urchins (Strongylocentrotus purpuratus and S. franciscanus) and a worm (Urechis caupo). Light from a Mazda standard projection lamp (gas filled, 30 volts, 30 amperes, with the tungsten filament radiating at about 3200°K) was passed through a slit 1×18 mm., 10 cm. from the filament, and through a monochromator consisting of 2 glass collimating lenses having a maximum thickness of 6 mm. each, and two 60° quartz prisms. An adjustable outlet slit was so arranged as to pass that portion of the spectrum lying within the approximate limits 0.8–1.2μ as determined by calculation from the known dispersion. The wave length of maximum energy was determined by the use of a small vacuum thermocouple and found to lie at about 0.8–0.9μ, as would be expected from the nature of the source. Rough calculation suggests that the energy flux in this region was probably of the order of magnitude of 0.1 cal. cm.−2 min.−1
Unfertilized eggs in a single layer were irradiated for periods of 15 to 45 minutes in special thin glass cells, controls in similar cells being placed 2 cm. away on the top of the monochromator. The experiments were done in darkness, the source being in a separate room, so that the controls received only that small amount of infrared and scattered visible light which passed through the monochromator and was reflected by the walls of the dark room. After irradiation the eggs were fertilized and further development watched under ordinary artificial illumination. For purposes of this article the term fertilization is used to designate the formation of fertilization membranes. The eggs of Urechis showed quantitatively identical effects upon this process and upon the disappearance of the germinal vesicle and subsequent cleavage.
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