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Thyroid gland in bat, Taphozous longimanus consists of two lateral lobes on the either side of trachea and are connected by isthmus. During the pre-breeding period large and medium sized follicles are predominant and small sized follicles are few while during the breeding period small and medium sized follicles are much more and large sized follicles are a few. Thyroid gland is composed of two different kinds of parenchymal cells, follicular epithelial cells and parafollicular cells (‘C’ cells or Calcitonin secreting cells or basal granular cell). ‘A’ type of follicular cells is lined by tall columnar epithelial cells which are highly secretory in nature, ‘B’ type of follicular cells is lined by low columnar epithelial cells and are secretory in nature while ‘C’ type of follicular cells is lined by low cuboidal epithelial cells. Parafollicular cells during the breeding period are more in number and larger in size than the pre-breeding period. During the breeding period, weight of thyroid gland, the mean diameter of follicles, colloid and height of epithelial cells of small, medium and large sized follicles are more, but not significantly different from that of the pre-breeding period.