Correct option is A
Explanation:
A is correct: Transplantation of the Xenopus dorsal lip induces formation of two embryonic axes with the same anterior-posterior polarity, as the host and graft axes align.
C is correct: The older dorsal lip in newts induces formation of a secondary tail, a classic developmental outcome.
B is incorrect: The anterior archenteron roof does not induce ectopic head structures but contributes to early mesoderm formation.
D is incorrect: Zebrafish dorsal shield transplantation results typically in two axes with same, not opposite, anterior-posterior polarity.
Information Booster:
The Spemann-Mangold organizer in amphibians (dorsal lip) is a key structure inducing embryonic axis formation.
Different stages of the dorsal lip have distinct inductive capacities; older dorsal lips induce tail structures.
Zebrafish embryonic shield is functionally analogous to the amphibian organizer but experiments show polarity conservation.
These experiments illustrate fundamental principles of embryonic induction and pattern formation.
