The Biology of Balanus balanoides. IV. Relation to Environmental Factors

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Abstract
1. Vertical traverses down the shore were worked at four localities in the Isle of Man, with varying degrees of wave-exposure, for which factor a coefficient is given.2. The upper limit of distribution is high water neaps in a sheltered place, and up to high water of extreme spring tides at greater waveexposure. The lower limit similarly drops with increasing exposure.3. Barnacles are largest and most abundant in a wave-exposed locality. The effect of wave-exposure may be reproduced by a current.4. In sheltered localities the optimum level for growth, mean size, etc., is at low water for newly settled barnacles, but moves progressively up to high water as they grow older. In a very exposed situation, however, the optimum is always at low water.5. In an exposed situation the gonads mature in their first year below about half-tide level, and in their second year above this level. With decreased wave-exposure the age of maturation rises, especially at high water until in a very sheltered place few barnacles mature at all.