胚囊,普通具有8个遗传上相同的单倍体核.Embryo has most commonly eitht genetically identical haploid nuclei.植入之后不久,胚囊的壁, 即滋养细胞含有两层细胞.Shortly after implantation the blastocyst wall, the trophoblast, consists of two layers of cells.存在于胚囊和胎座中的...
"Robinson Crusoe" is one of the most famous books in the world.《鲁宾逊漂流记》是一本世界名著。Defoe skilfully narrated the adventures of Robinson Crusoe on his desert island.笛福生动地叙述了鲁滨逊·克鲁索在荒岛上的冒险故事.Friday learned English so that Cruso...