By our guides in this matter, we are assured that the most important difference observed between man and the lower animals is the conscience; hence, if we would understand how it has been possible for man to rise to his present position, we must know something of the processes involved in the development of the social instincts, through which have originated conscience and a desire for the welfare of others outside of self. The importance of these instincts in the development of conscience is thus set forth by Mr. Darwin: Any animal whatever, endowed with well-marked social instincts, the parental and filial affections being here included, would inevitably acquire a moral sense or conscience, as soon as its intellectual faculties had become as well, or nearly as well, developed as in man. Sympathy, we are told, is the foundation-stone of the social instincts. From facts which are everywhere presented among the forms of life below man, it is evident that sympathy was developed at an early stage of animal life. It is doubtless strongly manifested in our ape-like progenitors, and it was probably this instinct which subsequently led to a community of interest and the coherence of the tribe. In a consideration, therefore, of this question of sex development and the origin of the progressive principle, if, as we are assured, sympathy constitutes the foundation-stone of the social instincts, and if it is to these instincts that we are to look for the origin of the moral sense, or conscience— a faculty which constitutes the fundamental difference between the human species and the lower orders of life—the question naturally arises: In which of the two diverging lines of sexual demarcation has arisen sympathy, or an interest in the well-being of others? For an answer to our question we must look carefully to the facts connected with the development of the sexes within one of which have been acquired characters tending toward the welfare of society, or of individuals outside of self; within the other, characters looking only toward selfish gratification. Within the former, the maternal instinct predominates; within the latter, passion. Mr. Darwin admits that “parental and filial affection lies at the base of the social instincts,” and gives as his opinion that this quality is the result of Natural Selection—that those individuals which bestowed upon their offspring the greatest care and attention, would survive and multiply at the expense of others in which this instinct was less developed. Therefore, in pursuing the inquiry of sex-function and sex-development, a question of considerable significance is at this point suggested: Within which parent is observed the greater tendency to bestow care and attention upon offspring?