We must first endeavour to make clear _what heredity is_. As a matter of fact we do not know; we are familiar only with a series of phenomena which we call heredity, just as we have a series of phenomena which we ascribe to the force of gravity, without knowing what gravity or its force actually is. If we consider only the phenomena of heredity, which are nowhere so completely and clearly put together as in Darwin’s works, we find that he presents so-called laws of heredity, that is, he has noted the most frequent phenomena of heredity, and thence deduced a law. If the phenomena in the conveyance of a disease to one’s descendants are to be called heredity, they must correspond with the rest of the phenomena of heredity. And looked at thus, we know of no specific disease which can be called hereditary. The conditions which are hereditary are all anatomical and physiological peculiarities of the organism. A bacillus which is living in the organism cannot be regarded as one of its anatomical or physiological peculiarities; it is a parasite. Now it is beyond doubt that parasites may be conveyed from parents to children. Such are the _Achorion Schönleini_, and the _Acarus Scabiei_. But this is no hereditary communication, it is simply a present from the parent to his child. But, it is objected, if the parasite is conveyed through the organs of generation during copulation, then it is no longer a present or an inoculation, it becomes hereditary. This appears to us a remarkable argument, that conveyance by means of the organs of generation can change the nature of the parasite and convert it into an anatomical constituent of the organism of parent or child. A parasite remains always a parasite, and since its conveyance from one adult to another is called infection, we cannot comprehend why its conveyance to an ovum or a fœtus should be indicated by another name. Were Baumgarten’s hypothesis correct, it should certainly be called a hypothesis of latent infection, and not a hypothesis of heredity. We said above that we knew of no specific disease which was hereditary. To this it will naturally be objected that syphilis is a typically hereditary disease. But we reply that syphilis is a disease communicable to children, but that it is not hereditary, and in order to maintain this statement we only need to place in parallel the phenomena of the conveyance of hereditary peculiarities and those of the communication of syphilis to children, in order to make it perfectly clear how different the two methods are. CONVEYANCE OF HEREDITARY CONVEYANCE OF SYPHILIS PECULIARITIES. TO CHILDREN. 1.--The hereditary peculiarity is usually limited to one sex, so that the male communicates Not the case in syphilitic his peculiarities to children. his male descendants, and the female hers to the female.