PSYCHIATRY, during recent years, has found it to its advantage to turn to a number of related sciences and allied branches of study for the explanation of a number of the peculiar symptoms of abnormal mental states. Of these related studies, none have been of greater value than those which throw light on the mental development of either the individual or the race. In primitive races we discover a number of inherent motives which are of interest from the standpoint of mental development. These motives are expressed in a very interesting symbolism. It is the duty of the psychiatrist to see to what extent these primitive motives operate subconsciously in abnormal mental conditions, and also to learn whether an insight into the symbolism of mental diseases may be gained, through comparison, by a study of the symbolism of primitive races. In the following communication one particular motive with its accompanying symbolism is dealt with. The application of these findings must be left with the psychiatrist in his clinical studies. A great many of the institutions and usages of our present day civilization originated at a very early period in the history of the race. Many of these usages are carried on in modified form century after century, after they have lost the meaning which they originally possessed; it must be remembered, however, that in primitive races they were of importance, and they arose because they served a useful end. From the study of these remnants of former days, we are able to learn the trends of thought which activated and inspired the minds of primitive people. When we clearly understand these motives, we may then judge the extent of their influence on our present day thought and tendencies. Now, in our present communication, we wish to deal with a motive which we find expressed very generally in primitive religion; this is the worship of sex. We not only find evidences of this worship in the records and monuments of antiquity, but our knowledge of the customs and practices of certain tribes, studied in comparatively modern times, indicates the presence of this same primitive religion. We feel that in sex worship we are dealing with an important motive in racial development, and our object at present is to give an account of its various phases.