THE EFFECT OF SALINITY UPON THE GROWTH OF EGGS OF FUCUS FURCATUS

¹ From the School of Biological Sciences, Stanford University

1. Fertilized eggs of Fucus furcatus f. luxurians have been reared in the dark at 15° C. in diluted and concentrated sea water.

2. When the salinity of the medium is between 60 per cent and 150 per cent that of normal sea water (sp. gr. 1.027), practically all of the eggs in a population form rhizoids and develop. The rate of elongation of the embryos, as measured at 4 days, is the same when the salinity is 90 per centor 100 per cent. When the salinity is greater or less, the growth rate is retarded as shown in the curve in Fig. 1.

3. As the salinity is reduced below 60 per cent or is increased above 150 per cent, the percentage of eggs which form rhizoids declines rapidly as shown in the blocks in Fig. 1. In 10 per cent and 20 per cent sea water the eggs burst and cytolyze. In concentrated sea water which inhibits development the eggs do not cytolyze and the developmental inhibition may be reversible.