In this article we will discuss about the gastrulation and formation of primary organ rudiments in fishes. In fishes the yolk formed in the oocytes during oogenesis initially does not differ substantially from the yolk in amphibian oocytes and eggs. It consists of yolk platelets lying in the cytoplasm and intermingled with other cytoplasmic components (mitochondria and the like). The [...]
In this article we will discuss about:- 1. Introduction to Metamorphosis in Amphibians 2. Causation of Metamorphosis in Amphibians 3. Tissue Reactivity 4. Induction. Introduction to Metamorphosis in Amphibians: In amphibians, metamorphosis is associated in typical cases with a transition from an aquatic to a terrestrial mode of life. Super-imposed on this change in environment, there is in the anurans [...]
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 [...]