The following account of the development of the gonophores and the formation of the egg in Myriothela harrisoni is based on a single female and several male specimens collected on the undersides of rocks below low-water mark at Bulli. forty miles south of Sydney. Although M. harrisoni is a dioecious form, it bears a distinct resemblance in its gross morphology to M. cocksi, which occurs under similar conditions on the coasts of Great Britain and western Europe. Both species have a chitinous investment by perisarc covering the hydrorhiza and forming a firm basis of attachment to the surface of the sub-stratum. This likeness is further emphasized by a study of the development of the gonophores and the formation of the egg, which follows through a series of stages very similar in their general details to those I have already described for M. australis.