[
1979]
Recombinant DNA methods have been used to characterize the genome of Caenorhabditis elegans. To determine if DNA rearrangements occur during somatic differentiation, fifteen randomly cloned Bam H1 fragments of somatic DNA were hybridized to Bam H1 digests of germ and somatic DNA's on Southern filters. In this way, 50 fragments representing 0.3% of the genome were compared and no size differences were detected. The DNA's of two interbreeding strains of C. elegans were also compared to determine the degree of evolutionary divergence. Fifteen percent of the fragments differed between the two strains. However, no differences could be found between the rDNA's. The DNA's of C. elegans and C. briggsae were compared and very little homology could be detected even though these species are morphologically very similar. The fragments that differ in size between the two interbreeding strains are being genetically mapped. These experiments suggest that non-random segregation of chromosomes might be occurring in