[2] The existence of sexual distinctions before puberty shows that the power of the internal secretions of the sexual glands does not account for everything. It is extremely interesting to recall in this connection that many times different investigators have observed in the testes of amphibia not only the different stages in the development of spermatozoa, but mature eggs. This interpretation of the observations was at first disputed, and it was suggested that the presence of unusually large cells in the tubes of the testes had given rise to the error, but the matter has now been fully confirmed. Moreover, in these Amphibia, sexually intermediate conditions are very common, and this should lead us to be careful in making statements as to the uniform presence of arrhenoplasm or thelyplasm in a body. The methods of assigning sex to a new-born infant seem most unsatisfactory in the light of these facts. If the child is observed to possess a male organ, even although there may be complete epi- or hypo-spadism, or a double failure of descent of the testes, it is at once described as a boy and is henceforth treated as one, although in other parts of the body, for instance in the brain, the sexual determinant may be much nearer thelyplasm than arrhenoplasm. The sooner a more exact method of sex discrimination is insisted upon the better. As a result of these long inductions and deductions we may rest assured that all the cells possess a definite primary sexual determinant which must not be assumed to be alike or nearly alike throughout the same body. Every cell, every cell-complex, and every organ have their distinctive indices on the scale between thelyplasm and arrhenoplasm. For the exact definition of the sex, an estimation of the indices over the whole body would be necessary. I should be content to bear the blame of all the theoretical and practical errors in this book did I believe myself to have made the working out of a single case possible. Differences in the primary sexual determinants, together with the varying internal secretions (which differ in quantity and quality in different individuals) produce the phenomena of sexually intermediate forms. Arrhenoplasm and thelyplasm, in their countless modifications, are the microscopic agencies which, in co-operation with the internal secretions, give rise to the macroscopic differences cited in the last chapter.