lower cavity of the bladder. This, excepting a constriction near its fundus, had the usual shape; but inwardly the mucous membrane formed a partial partition between the upper and lower portions. The two sets of ureters opened, one just above and the other just below this partition.
"There were two pairs of testes, one resting on the kidneys or quite near them, and the other just at the en trance of the internal abdominal ring on the front of the foetus. Each testis had an epididymis and vas deferens, but in neither case was it traced to its connection with the bladder. There were, however, to be seen just below the septum of the bladder, mentioned above, three openings, which probably belonged to the vasa deferentia, one pair entering the bladder separately, while the other united and entered through a single opening.
"The descriptions of double monsters by many different observers all show that the tendency is to symmetrical de velopment, so that when an organ ordinarily single becomes double the two organs are always right and left. This is well seen in the specimen just described, in the existence of a right and left heart, right and left stomach, spleen, etc. In the cases where organs, commonly double, are increased in number, we may have either a third organ, or two entire ones. In the first case the law of symmetry is manifest in a most striking manner. For all such third organs, if not compound in structure, are divisible into right and left halves, and half from a different foetus, and repeating each other oppositely. If, however, they are made up of many parts, as a limb, then the individual parts repeat each other in a similar way. In the arm al ready described, the muscles repeat and balance each other exactly throughout, and the same is mostly true of the legs.
"The force, whatever it be, which regulates the distri bution of matter in a normal or abnormal embryo, always acts symmetrically, and if we look for anything among known forces, analogous to it, it is to be found, if any where, in those known as polar forces. The essential fea tures of polarity, as in symmetry, are antagonism, either
