In this article we will discuss about the development of general body form of vertebrates. While the various organs are being formed, the shape of the embryo as a whole undergoes far-reaching changes. During the period of organogenesis, in the case of the vertebrate embryo, the main changes are: i. Elongation of the body. ii. Formation of the tail. iii. [...]
The changing appearance of the embryos, especially during organogenesis, invites the distinguishing of certain stages which can be referred to when it is desired to indicate how far an embryo has progressed in its development. Tables of "normal stages" have been worked out for a number of species of animals, especially those that are most often used for research. In [...]
The relation between the archenteron and the definitive alimentary canal is very different in vertebrates with complete cleavage from that in vertebrates with incomplete (meroblastic) cleavage. The Relation in Lower Vertebrates: The archenteron in Amphioxus is originally lined with presumptive endoderm, presumptive mesoderm, and presumptive notochordal cells. When the notochord and the mesoderm are segregated from the endoderm, the latter [...]