The present investigation was carried out on 60 camel embryos and foetuses of different CVR lengths ranging from 1.2-112 cm. Twenty-four foetuses were used for gross anatomical description of both thyroid gland and thymus. The specimens were fixed by injeThe histogenesis of the thyroid, parathyroid and thymus glands was performed on 107 samples from 36 camel embryos and foetuses. Serial sections of 4-6 micrometer thickness were obtained and stained with different histological stains.The obtained results were segregated into three parts as follow:Part I: Thyroid gland• Gl. thyroidea of camel foetuses was formed of two oval or elongated fusiform lobes which were connected caudally by a narrow isthmus.• Gl. thyroidea was arterially vascularized through A. thyroidea cranialis et caudalis.• Gl. thyroidea was drained into V. jugularis externa through V. thyroidea cranialis et caudalis.• At 1.2 cm CVR length camel fetus, the thyroid primordia appeared as a simple bilobed cell mass and the ultimobranchial body appeared as an elongated empty tube lined by stratified layers of closely arranged cells.• At 7cm CVR length, the thyroid primordia were surrounded by a thin layer of future capsule, and the future thyroid follicles began to appear in few numbers in the thyroid primordia but not present in the isthmus.• At 11cm CVR length, the ultimobranchial cysts increased in number with different sizes, the primitive follicles began to appear inbetween the cellular cords in the isthmus and at 17cm CVR length, the few primitive thyroid follicles showed an empty lumen• At 20 cm CVR length, the colloid began to appear inside few follicles, and the thyroid primordia divided into several demarcated lobules.• At 39 cm CVR length, some follicles contained lightly stained colloid, while others showed darkly stained colloid. The colloid material of some follicles might contain numerous vascules of various sizes.• from 50-112 cm CVR length, ultimobranchial follicles began to appear inside the ultimobranchial body, the latter showed degeneration as occurred complete loss of cytoplasm, pyknosis, karyolysis and became surrounded by thick layer of collagen fibers.Part II: Parathyroid gland• At 1.2 cm CVR length camel fetus, there were four primordia of parathyroids, one pair developed from 4th pharyngeal pouch (parathyroids IV or internal parathyroid glands), the other pair arose from 3rd pharyngeal pouch (parathyroids III or external para• At 2.5 cm CVR length, the parathyroid primordia were observed as short separated curved cords with mesenchymal cells inbetween.• At 4 cm CVR length the parathyroid primordia became surrounded by a thin capsule with flattened mesenchymal cells. Some cords showed internal proliferation (endoproliferation).• At 9.5 cm CVR length, the primordia of parathyroid IV showed branching anastomosing cellular cords. The parathyroid III was observed caudal to the level of parathyroid IV.• At 11cm CVR length, some of the parathyroid parenchymal cells were arranged in follicle-like manner and some cords enclosing blood sinusoids.• At 12.5 cm CVR length, some cells proliferated and aggregated in groups inbetween the cords (exoproliferation).• The parathyroid III primordia were embedded inside the thymus parenchyma, during the serial sections of Pars thoracalis thymi of camel fetuses at 17,25,55 and 58 cm CVR lengths.• At 20 cm CVR length, part of the parathyroid primordia was mostly embedded inside the thyroid parenchyma and other part on the surface of thyroid primordia.• At 65 cm CVR length, few cells with a lightly stained cytoplasm and containing small deeply stained pyknotic nucleus (future oxyphil cells) could be observed inbetween the chief cells.• At the late stage of parathyroid development, the gland was surrounded by a thin connective tissue capsule. The parenchymal cells were arranged into three types, light and dark chief cells in addition to oxyphil cells.Part III: Thymus• The left thymus consisted of 3 portions; Pars cranialis thymi, Pars cervicalis thymi and Pars thoracalis thymi. The right thymus consisted of 2 portions; Pars cranialis thymi and Pars cervicalis thymi.• The thymus was arterially vascularized via branches from A. carotis communis, A. thoracica interna sinistra and A. subclavia sinistra.• The thymus was drained via V. jugularis externa, V. cava cranialis and V. costocervicalis.• AT 1.2 cm CVR length camel fetus, the thymic primordia appeared to be originated from the ventral wing of the third pharyngeal pouch as a tubular structure. It extended in the neck but not reach the thorax.• At 2.5 cm CVR length, the right and left thymus extended on either side of the primitive oesophagus in the neck, then in the precardiac mediastinum, the two cords enlarged to from the thoracic part of the thymic primordia.• In the cervical region, the right thymic primordia gradually shifted ventral to the trachea to gain its left side where it accompanied the left thymic primordia till reach the thoracic inlet in camel fetus at 4 cm CVR length.• At 6 cm CVR length, the thymic primordia showed few lymphoblasts, at 9.5 cm CVR length the thymus showed infilteration of lymphocytes with less distinct cortex and medulla.• At 11 cm CVR length, Hassall’s corpuscles began to appear as acidophilic mass which was surrounded by a flattened degenerated epithelioreticular cell layer.• In camel fetuses from 30 to 36 cm CVR length, Hassall’s corpuscles showed degenerated cells with pyknotic nuclei and presence of some vacuoles.4- There was a significant difference (P:S0.05) in frequencies of heading,butting, mutual grooming between tethered (0.21±0.22, 0.0 and6.23±0.87 bout/12 hr respectively) and loose group (0.84±0.10,4.00±6.40 and 3.92±0.47 boutll2 hr respectively).