597. This #kanjipuzzle is about evolution. Start with one character, add a few strokes, and get another, then repeat. 一 -> ? -> ? -> ? -> ? -> ? -> ? -> ? -> 韻

Answer:

一  ICHI, ITSU, hito(tsu) - one

二  NI, futa(tsu), futa - two

コ  Katakana "Ko"

口  KOU, kuchi - mouth

日  NICHI, JITSU, hi, ka - sun, day

目  MOKU, me - eye

貝  KAI - shellfish

員  IN - member

韻  IN - rhyme