Which new characters are inherited?--Examples of somatic modifications--Use and disuse--The problem stated--Special conditions in mammals--Three fundamental questions--External influences may directly affect the germ-cells--Such effects improbable in warm-blooded animals--Poisons may affect the germ-plasm--How can somatic modifications be registered in germ-cells?--Persistence of Mendelian factors argues against such a mode of inheritance--Experiments on insects--On plants--On vertebrates--Epilepsy in guinea-pigs--Effects of mutilations not inherited--Transplantation of gonads--Effects of body on germ, general not specific--Certain characters inexplicable as inherited somatic acquirements--Neuter insects--Origin of new characters in germinal variation--Sexual reproduction in relation to new characters--Many features of an organism characterized by utility--Germinal variation a simpler and more inclusive explanation--Analysis of cases--Effects of training--Instincts-- Disease--Reappearance not necessarily inheritance--Prenatal infection not inheritance--Inheritance of a predisposition not inheritance of a disease--Tuberculosis--Two individuals of tubercular stock should not marry--Special susceptibility less of a factor in many diseases--Deaf-mutism--Gout--Nervous and mental diseases--Other disorders which have hereditary aspects--Induced immunity not inherited--Social, ethical and educational significance of non-inheritance of somatic modifications--No cause for discouragement--Improved environment will help conserve superior strains when they do appear. VI PRENATAL INFLUENCES 151 All that a child possesses at birth not necessarily hereditary-- The myth of maternal impressions--Injurious prenatal influences-- Lead poisoning--The expectant mother should have rest--Too short intervals between children--Expectant mothers neglected-- Alcoholism--Unreliability of most data--Alcohol a germinal and fetal poison--Various views of specialists on the effects of alcoholism on progeny--The affinity of alcohol for germinal tissue--Innate degeneracy versus the effects of alcohol-- Experimental alcoholism in lower animals--Further remarks on the situation in man--Much inebriety in man due to defective nervous constitution--Factors to be reckoned with in the study of alcoholism--Venereal diseases--The seriousness of the situation-- Infantile blindness--Syphilis--Some of the effects--A blood test-- Many syphilitics married--Why permit existing conditions to continue?--Ante-nuptial medical inspection--The perils of venereal disease must be prevented at any cost--Bad environment can wreck good germ-plasm. VII RESPONSIBILITY FOR CONDUCT 195