embryonic

adj. of or pertaining to an embryo; undeveloped

An embryo (Greek: , plural ) is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination. In humans, it is called an embryo from the moment of fertilisation until the end of the 8th week of gestational age, whereafter it is instead called a fetus.
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Adjective
1. of or relating to an embryo; "the embryonic membrane"
(synonym) embryonal
(pertainym) embryo, conceptus, fertilized egg
2. of an organism prior to birth or hatching; "in the embryonic stage"; "embryologic development"
(synonym) embryologic, embryonal
(similar) immature
3. in an early stage of development; "the embryo government staffed by survivors of the massacre"; "an embryonic nation, not yet self-governing"
(synonym) embryotic
(similar) early

(a.)
Of or pertaining to an embryo; embryonal; rudimentary.
  

Having to do with an embryo, which is an early stage in the development of a plant or animal.