RESUMEN
In a search for new vital stains to reveal the microanatomy of nudibranch mollusks, the slow or very low solubility of many dyes in sea water posed a serious problem. Preliminary dissolution in tap water proved impractical. Hydroxyethyl lactamide, an odorless liquid and dye solvent was found ideal since it permits immediate attainment of saturated solutions of dyes in sea water. Since hydroxyethyl lactamide passed the severe "eolid nudibranch test" and has been found nonirritating for the very sensitive rhinophorial structures, and furthermore since it has been used by the pharmaceutical industry as a vehicle in antibiotic preparations, it appears to be an ideal universal dye solvent for general use in vital staining. It has been used extensively in unpublished research by the writer on vital staining of nudibranchs. It has a low order of physiological activity and can be regarded an essentially inert when used in vital staining.