Each of the three layers of cells (ectoderm, mesoderm, and endoderm) that are formed in the early embryo.
- ‘During gastrulation, animals form a structure called the blastopore, which is where migrating tissues tuck themselves inward to establish the three germ layers of the embryo.’
- ‘Flatworms are unsegmented, bilaterally symmetrical worms that lack a coelom but that do have three germ layers.’
- ‘This process, called induction, culminates in the formation of a thickening in the ectoderm germ layer known as the neural plate.’
- ‘The third germ layer, the endoderm, which is located at either end of the embryo, and which we do not consider here, gives rise to the mid-gut.’
- ‘Muscle is one of the basic mesodermal tissues in bilaterians, and it is easy to see how this very efficient arrangement could lead to the formation of an entirely new germ layer.’
We take a look at several popular, though confusing, punctuation marks.