Professor Penta has for many years been occupied in studying criminals in the prisons of Naples, one of the most favourable regions in Europe for such studies. In the present paper he sets down some of the latest of his general conclusions on the subject of the nature of criminality. These conclusions differ widely in many respects from those of Lombroso. He notices in the first place that he finds a very great difference between those prisoners who are confined in establishments reserved for minor offenders and those, convicted of more serious offences, who are confined in the convict prisons; the first are a much more dangerous class than the second, much more incorrigible, and much more often lacking in moral sense. He finds also that while the first group—the more dangerous persons who only commit slight offences,—come mainly from the cities, the others come from the country. The individuals of the first group also belong in much larger proportion to the class considered by Lombroso to be merely insane. So that the offence and its punishment, taken by themselves, furnish a very fallacious criterion for diagnosis and treatment.