英语翻译However,in its absence the overall number of placodes is diminished and they do not progress past the hair germ stage,although a small number of terminally differentiated hair cells can still be detected.主要是progress past the germ stage 这句past是什么情况.its好象是SHH
问题描述：
英语翻译
However,in its absence the overall number of placodes is diminished and they do not progress past the hair germ stage,although a small number of terminally differentiated hair cells can still be detected.
主要是progress past the germ stage 这句past是什么情况.
its好象是SHH
答
然而,在它的总体数量仍placodes没有减少,他们不进步的头发生殖阶段过去,尽管少量的垂死的分化细胞仍能发现头发。
答
germ应该指起源萌发的意思.
进化到有毛发阶段.past:超越,超过.
因为脊椎动物的进化过程是由水生的鱼,到两栖动物,再到哺乳动物和鸟类,而两栖动物是没有毛发的,就如青蛙,鳄鱼那样.哺乳动物和鸟类才有毛发,属于进化的高级阶段.
无论如何,在缺少水的情况下总的基板数目减少了并且他们还没有进化到有毛发萌生的阶段.虽然人们已经在化石中发现了少量的末期分化出的毛发细胞.