[
1996]
In the nematode model organism Caenorhabditis elegans developmental processes can be anaylzed at various levels. The invariance of cell lineage allows a high-resolution morphological description of development and an experimental approach by ablation of individual cells. Isolation and characterization of genetic mutations reveal the basis of the genetic program underlying particular developmental processes. DNA-mediated transformation can be used to anaylze the function of cloned genes and thus finally generate also a molecular understanding of the process under investigation. Evolutionary approaches to development are rare and so far consist only of a subset of techniques used in the reference model system. By using the complete set of techniques from the model organism, including genetics, in related but morphologically distinct species, one can get a detailed comparison of a developmental process. Here we describe our attempt to establish the techniques known in the model organism Caenorhabditis of the Rhabditidae in other free-living nematodes, including Pristionchus pacificus of the