The hollow collection of undifferentiated cells that occurs after fertilization and initial mitosis is called a

Blastula

Explanation:

This mass of cell – called blastomere- surrounds a fluid-filled cavity-blastocoele- formed in the very early stages of development of an embryo in animals, after fertilization and the formation of a zygote. Blastomere cells have high potency and can differentiate into any type of cell.

as the gila monster consumes the eggs or young of the desert cottontail and gambel's quail, thus its main food supply is only accessible for a restricted time duration every year. however, for this, the gila monsters exhibit three adaptations, which elevate their survival rate in the desert condition.  

first, is that they possess huge bodies, and can consume greater concentrations of food during a small period. secondly, they require to feed infrequently as they can accumulate fat in their tails. ultimately, their rate of metabolism is very low, so that they can burn their reservoirs of fat gradually.