Abstract
Sea urchin eggs, fish eggs, and adult copepods showed different sensitivity towards aromatic hydrocarbons of the naphthalene type. Methylated naphthalenes were, however, more toxic than naphthalene. The toxicity was apparently not dependent on the number of methyl groups, but rather on their position on the naphthalene molecule. Ultrastructural studies of exposed sea urchin embryos did not reveal specific effects at the cellular level.