Observations with the microscope may furnish a good basis for the diagnosis and classification of tumors, when such observations furnish the most positive, characteristic and definite evidence that is obtainable. When the gross appearances, symptoms and clinical course of the case are more definite and distinct, they furnish a better basis for diagnosis than do the appearances revealed by the microscope. The best possible basis includes both microscopic and clinical evidence. A recent writer has pointed out that a need of our day is men who are both clinicians and pathologists, not mere clinicians on the one hand, or mere workers in the mortuary and laboratory on the other. The specializing process which leaves the pathologist ignorant of clinical medicine and the clinician ignorant of pathology has been harmful in many instances, but in none more harmful than in the case of malignant tumors arising in the retina.