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> dss INTRODUCTION Gametes are haploid structures, Fusion of a male and a female gamete is called fertilisation. It leads to format; zygote which is a diploid structure. In mammals, the process of fertilisation takes place in oviduct. After the fory of zygote, it starts to move from oviduct towards the uterus. With the movement, zygote also begins to divide by mitotic division. As a result of successive divisions, different stages of embryonic development are formed. Mo which is the first Stage in embryonic development, consists of 8-16 embryonic cells (blastomeres). As morula mo further into the uterus, the blastomeres continue to divide and form around 64 embryonic cells. These cells get a in a layer and froma hollow ball-like structure. This stage of embryo is referred to as a blastula. Further differentiation in blastula leads to development of a inner group of cells called inner cell mass and a fluid-filled space called the blastocoel. This represents advanced Stage of blastula (also called blastocyst). At this stage, embryo gets embedded into the wall of uterus, Uterus Oviduct Zygote Ovulation AIM To study T.S. of blastula through permane MATERIALS REQUIRED Permanent slide of T.S. of blastula and compound microscope. PRINCIPLE The zygote undergoes a few cycles of mitotic divisions to form a spherical cluster of cells. This ball-like stage morula is the first stage in embryonic development. In morula, the embryonic cells continue to divide and d of a cavity, which is filled with a fluid, takes place. Now this stage of embryonic development is called bl internal structural features of blastula can be observed in its transverse section. 
