3: Invertebrate Model Organisms Last updated Jan 4, 2021 Save as PDF 2.4: Regeneration 3.1: Planaria Page ID42909 ( \newcommand{\kernel}{\mathrm{null}\,}\) 3.1: Planaria3.2: C. elegans3.3: Fruit flies3.3.1: Segmentation - Organizing the Embryo3.3.2: Homeobox Genes3.4: Sea urchin