1 Introduction: Male Sexual Differentiation.- 1.1 Development of the Androgen-Dependent Structures of the Genitals.- 1.2 Testicular Descent.- 1.2.1 Significance.- 1.2.2 Morphological Principles.- 1.2.3 Processes.- 1.2.4 Regulatory Mechanism.- 1.2.5 Endocrinology of Cryptorchidism.- 1.2.6 Experimental Studies.- 2 Materials and Methods.- 3 Results.- 3.1 Controls.- 3.1.1 Qualitative Macroscopic Examination of the Adult Animals.- 3.1.2 Qualitative Microscopic Examination of the Adult Animals.- 3.1.3 Quantitative Microscopic and Macroscopic Examinations of the Adult Animals.- 3.1.4 Male Fetuses.- 3.2 Cyproterone Acetate.- 3.2.1 Qualitative Macroscopic Examination of the Adult Animals.- 3.2.2 Qualitative Microscopic Examination of the Testes of the Adult Animals.- 3.2.3 Quantitative Microscopic and Macroscopic Examinations of the Adult Animals.- 3.2.4 Male Fetuses.- 3.3 Ethinyl Estradiol.- 3.3.1 Qualitative Macroscopic Examination of the Adult Animals.- 3.3.2 Qualitative Microscopic Examination of the Adult Animals.- 3.3.3 Quantitative Microscopic and Macroscopic Examinations of the Adult Animals.- 3.3.4 Male Fetuses.- 3.4 Cyproterone Acetate and Ethinyl Estradiol.- 3.4.1 Qualitative Macroscopic Examination of the Adult Animals.- 3.4.2 Qualitative Microscopic Examination of the Adult Animals.- 3.4.3 Quantitative Microscopic and Macroscopic Examinations of the Adult Animals.- 3.4.4 Male Fetuses.- 4 Discussion.- 5 Summary.- References.