Bouin’s fixative is a particularly good choice for worms because it penetrates dense tissues well and is extremely good for fixing antigens. Like all strong fixatives, however, it is unsuitable for some antibody-antigen pairs. In such cases, the length of time in the Bouin’s fixative can be shortened, or paraformaldehyde fixation can be used instead. - [Read Fixing Caenorhabditis elegans in Bouin’s Fixative Protocol]
Common method for fixing worms is to use paraformaldehyde. This method provides a gentler fixation than the Bouin’s method, but often requires the use of collagenase. This method is particularly good for examining adult worms. - [Read Fixing Caenorhabditis elegans in Paraformaldehyde Protocol]