Ranging from 100 to 200 microns across , the width of several human hairs , these microscopic fossils are surprisingly complex and constitute almost a textbook example of a bilaterian , including the three major tissue layers ( the endoderm , mesoderm and ectoderm familiar from high school biology texts ) , the presence of a gut with a mouth and anus , and paired coeloms ( body cavities ) surrounding the gut 這些微化石的大小為100 ~ 200微米,相當于幾根頭發的寬度, ?們看起來出奇復雜,而且簡直就像兩側對稱動物的教科書般,展示了各種特徵:包括三個主要的組織層(內胚層、中胚層及外胚層,都是中學生物課本中熟悉的名詞) ,前后連接口部與肛門的腸腔,腸腔外還圍繞著成對的體腔。
英文解釋
the outer germ layer that develops into skin and nervous tissue 同義詞:exoderm, ectoblast,
百科解釋
Ectoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the mesoderm (middle layer) and endoderm (most proximal layer), with the ectoderm as the most exterior (or distal) layer.