结果表明，单环刺消化道起源于原肠胚期内陷而成的原肠腔；

The results showed that, the digestive canal initiated from the gastrocoele, which was formed by invagination at gastrula stage.

除了观察正常细胞的原肠胚形成，科学家们还观察了突变细胞。

In addition to looking at normal gastrulation, the scientists also looked at what happens to gastrulation when mutations occur.

原肠胚形成过程中，由上胚层细胞增殖产生的一部分细胞在上、下胚层之间形成的第三层细胞。通常形成骨骼、肌肉、结缔组织、心脏、造血系统、肾脏和其它器官。

Mesoderm --- The middle germ layer in the early embryo; the source of cells that go on to make bones, muscles, connective tissue, heart, hematopoietic system, kidney, and other organs.