ANATOMY

Detailed explanation-1: -The fourth cleavage is meridional and unequal holoblastic. The micromeres which do not contain yolk now divide faster than macromeres which contain yolk. So, the correct answer is ‘Double meridional’.

Detailed explanation-2: -Fourth cleavage involves two synchronous meridional divisions resulting in the formation of 16 blastomeres. Fifth cleavage involves two simultaneous latitudinal divisions resulting in the formation of 32 blastomeres. The divisions after the fifth cleavage becomes very irregular and asynchronous.

Detailed explanation-3: -Cleavage in most frog and salamander embryos is radially symmetrical and holoblastic, just like echinoderm cleavage. The amphibian egg, however, contains much more yolk.

Detailed explanation-4: –The vertical cleavage occurs when a furrow does not pass through the median axis from the animal pole towards the opposite pole.-Horizontal plane cleavage, the furrow runs through the cytoplasm through the equatorial plane.

Detailed explanation-5: -The first cleavage occurs shortly after the zygote nucleus forms. A furrow appears that runs longitudinally through the poles of the egg, passing through the point at which the sperm entered and bisecting the gray crescent. This divides the egg into two halves forming the 2-cell stage.