ANATOMY

Detailed explanation-1: -However, because of the vegetally placed yolk, this cleavage furrow in amphibian eggs is not actually at the equator, but is displaced toward the animal pole. It divides the frog embryo into four small animal blastomeres (micromeres) and four large blastomeres (macromeres) in the vegetal region.

Detailed explanation-2: -The pigmented cells (micromeres) are found in the anterior half while the yolky megameres are present in the posterior half. As has been already pointed out, the blastocoel lies entirely in the anterior half. The blastula of frog is hollow and has a very well developed blastocoel.

Detailed explanation-3: -Mesomeres, macromeres and micromeres originate at 4th cleavage, which includes an asymmetric cleavage in the vegetal half of the embryo.

Detailed explanation-4: -The micromeres contain no yolk and macromeres contain large amount of yolk. Fourth cleavage involves two synchronous meridional divisions resulting in the formation of 16 blastomeres.

Detailed explanation-5: -So, the correct option is ‘Coeloblastula’.