Observations made on sickle cells with phase contrast and with the electron microscope lead to the following conclusions.
1. When the red cell sickles, its oscillatory movements cease.
2. Spherical red cells give rise to a special form of sickle cell.
3. Myelin forms, whether attached to the cell or free, become rigid when the tension of oxygen is reduced.
4. The electron microscope, combined with the technic of moulage, shows that the sickle cell contains striated rod-like structures, which give a characteristic appearance to the surface of the sickle cell.
5. Agglutination by appropriate antisera does not occur to any extent in sickled cells, because these rigid structures do not form myelin forms. This is additional evidence of the importance of the formation of viscous surface layers already described as part of the mechanism of agglutination.