THESAURUS
basal
ab ovo, aboriginal, basic, basilar, beginning, bottom, bottommost, central, constituent, constitutive, crucial, elemental, elementary, embryonic, essential, foundational, fundamental, generative, genetic, germinal, gut, in embryo, in ovo, lowermost, lowest, material, nethermost, of the essence, original, pregnant, primal, primary, primeval, primitive, primordial, pristine, protogenic, radical, rudimental, rudimentary, seminal, substantial, substantive, underlying, undermost