This lab will introduce students to a simple bioassay that will allow them to explore the effects that a chemical's concentration has on the level of toxicity. By relying on morphological examination of sponges hatching from gemmules that are smaller than a millimeter in diameter, this module will help students develop their microscopy skills. Our major aim, however, is to have students strengthen their ability to design and test their own hypotheses. We recently reported that several potential endocrine disrupters cause gross morphological defects in developing sponges (Hill et al. 2001). As can be.
