Whether in this case also the disease germs are transmitted through the male sex-cells is not proved, as far as I am aware, but that this can happen is shown by the transmission of syphilis from father to child. That in this case, also, the exciting cause of the disease is a micro-organism cannot be doubted, although it has not yet been proved. Thus even the minute spermatozoon of Man can contain microbes, and transmit them to the germ of a new individual. This discussion of scientific questions ought not to be brought down to the level of a play upon words, by bringing forward cases like the above as evidence for the inheritance of 'acquired characters,' as was done, for instance, by M. Nussbaum, who cited as a proof of this the migration of the alga-cells which live in the endoderm of the green freshwater Hydra into the ovum, which is originally colourless, and originates in the ectoderm of the animal (Fig. 35_B_, p. 169, vol. i). It seems to me better to make a precise distinction between the transmission of extraneous micro-organisms through the germ-cells and the handing on of the germ-plasm with the characters inherent in its structure. Only the latter is inheritance in the strict scientific sense, the former is infection of the germ. Still less than the cases of inherited traumatic epilepsy can the morbid constitution of the children of drunkards be regarded as a proof of the inheritance of somatogenic characters, though this has often been maintained. I will not lay any stress on the fact that the allegation itself is, according to the most competent observers, such as Dr. Thomas Morton[12], far from being established. But even if it were quite certain that the numerous diseases of the nervous system, amounting sometimes to mania, which are frequently observed in the children of drunkards, were really _caused_ by the drinking of the parents, it ought not to be overlooked that we have here to do not with the hereditary transmission of somatic variations, but of variations _directly_ induced in the germ-plasm of the reproductive cells, for these are exposed to the influence of the alcohol circulating in the blood, just as any other part of the body is. That by this means variations in the germ-plasm can be brought about, and that these may lead to morbid conditions in the children cannot be denied, and ought not on _a priori_ grounds to be called in question. For we are acquainted with many other influences--climatic, for instance--which directly affect and cause variation in the germ-plasm. Whether this is so in the case of drunkenness, and in what manner it comes about, whether through direct action of the alcohol, or through infection of the germ with some microbe, we must leave to the future to decide; the whole question is out of place here; it can in no way help us to clear up the problem with which we are now occupied.