The first centres of ossification appear about the seventh week on the clavicle and lower jaw. At this time the kidneys and renal capsules begin to appear. The only trace of muscular fibre is in the diaphragm. The vertebral arches are not yet closed in, and the ribs appear like little streaks; the liver is very large and granular. The stomach is assuming somewhat of its normal form; the urinary bladder is enclosed, but the anus is imperforate. At this time the embryo is about an inch in length. At two months the rudimentary organs of generation may be distinguished, but their development does not clearly show the sex. The embryo is from one and a half to two inches long and weighs near half an ounce, the head forming two-thirds of the whole. After this period the different parts are developed with tolerable rapidity. At _ten weeks_ the embryo is about two and a half inches in length. At the end of the _third month_ it is from five to six inches long and weighs from three to four ounces. The thorax is closed at all points but is only slightly developed; the cord contains no intestines, and its spiral turns are evident; the nails are beginning to appear; the sex is distinct, and the skin acquires some consistence. At the fourth month the fœtus is six to eight inches in length, and weighs from seven to eight ounces. A fœtus born at this period might live for an hour or two. At _five months_ the length of the body, including head and feet, is from eight to ten inches, and weighs from eight to eleven ounces; at _six months_ the weight is about one pound, and the length is eleven to twelve and a half inches. At _seven months_ the fœtus is from twelve and a half to fourteen inches long and weighs from three to five pounds. The hands and feet, including the nails, are developed; all its parts are tolerably firm, and their respective dimensions better proportioned than formerly. The scrotum usually contains one or both testicles, they having descended through the inguinal ring, from their original place near the vertebral column; the eyelids are partly open; the skin is very red and covered with down. Many children live and are reared that are born at seven months. The length of a fœtus born at term is eighteen or nineteen inches, though the utmost limit is more than two feet. The usual weight is from six to seven pounds; children have been born, however, that were as much as eighteen pounds in weight. I suspect that this will never occur unless the term has been extended beyond the usual period.