i) When Hydra is transversely sliced into annular segments.

Answer- It is also observed that if the hydra is transversely sliced into annular segments, then each segment gives rise to a hypostome distally (anteriorly ) and a basal part proximally (posteriorly).Sometimes however, it has been noticed that a short segment, cut just below the
hypostome, will regenerate a hypostome with mouth and ring of tentacles at both ends, giving rise to a 'bipolar hydra'.
Even in the normal course of life hydroid polyps are in a 'continuous state of
regeneration'. The cells comprising the tentacles and hypostome and the basal pedal disc get continuously worn out. discarded and replaced by cells shifting distally and proximally from an area called the growth zone, located below the ring of tentacles.

The growth zone is easily identified by the presence of large number of interstitial cells
In Hydra, thus there is a steady migration of cells from the middle of the body in both direction to the hypostome and tentacles and to the peduncle and foot.

Regeneration process begins with the closure of the wound by contraction of the epitheliomuscular cells of the epidermis. After this the damaged surface is covered by ectoderm which forms a sheet of epithelial cells. In the next few hours more than the usual number of cells are given off from the growth zone towards the cut surface of the damaged area. which may be towards the oral or the aboral side of the body. Regeneration of each piece will occur to form complete miniature hydras even in complete absence of cell division in either piece.

ii) The scientist McKinnel (1962) in his experiments transplanted the blastula nuclei into enucleated eggs.

Answer- In 1952 Robert Briggs and Thomas J. King published their article, “Transplantation of Living Nuclei from Blastula Cells into Enucleated Frogs’ Eggs,” in the Proceedings of the National Academy of Sciences, the culmination of a series of experiments conducted at the Institute for Cancer Research and Lankenau Hospital Research Institute in Philadelphia, Pennsylvania. In this paper Briggs and King examined whether nuclei of embryonic cells are differentiated, and by doing so, were the first to conduct a successful nuclear transplantation with amphibian embryos. Previously nuclear transplantation had only been performed using amoebae cells. Briggs and King believed that by removing the egg nucleus and replacing it with a differentiated cell, they could study nuclear differentiation. During the experiment, they used two different species of frogs, Rana pipiens and Rana catesbeiana, to study and test whether the nucleus is differentiated. The nuclear transplantation performed in the experiment would later be referred to as cloning.

Although nuclei are equivalent during the early phases of development, previous studies regarding whether nuclei in various blastomeres continue to be alike or become differentiated did not exist. Thomas Hunt Morgan hypothesized that nuclei might differentiate according to their location in the cytoplasm, and that nuclear changes might achieve different consequences in the cytoplasm during cell differentiation.