I can't find a detailed illustrative discussion on Gastrulation of frog in any of the highly recommended books like Gilbert and Wolpert. All I've found is a book called Simplified Course In Bsc Zoology Chordate Embryology And Histology that though has a detailed explanation on this topic but after reading it I'm left with several questions like-
1. What happens to the inner cell mass of blastula? What's its fate?
2. Are the presumptive mesodermal cells present as a part of blastoderm?
3. What decides the anterior-posterior axis of frog embryo?
I've thoroughly searched the google.books and google.com with no luck, where can I find a good book or a paper explaining the mentioned topic. It would be great if the explanation does deep into the molecular level.