例句與造句

1. 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(fā)的寬度， ?們看起來出奇復雜，而且簡直就像兩側(cè)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(nèi)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。
2. It's difficult to find ectoderm in a sentence. 用ectoderm造句挺難的