如果是运动的，蛋壳形成条纹。
这种海绵状组织是形成蛋壳的钙质来源。
This spongy tissue serves as a source of calcium for eggshell formation.
研究人员发现，蛋壳只有在一种蛋白质的催化下才能形成，而这种物质只存在于鸡的卵巢内。
Researchers found that the formation of egg shells relies on a protein found only in a chicken’s ovaries, according to The Sun of London.
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