gonad morphology variant rachis morphology variant rachis morphology abnormal Any variation in the form, structure or composition of the nucleus-free core of germ line cytoplasm in the gonad compared to control animals. In the C. elegans germline, nuclei exiting mitosis and entering meiosis are arranged along the cortex of the germline, partially enclosed by cellular membrane, forming a nucleus-free core of germline cytoplasm, called the rachis. WBPhenotype:0001940 C_elegans_phenotype_ontology