"When Huxley wrote, the embryological history of anthropoid apes was practically unknown. Darwin, Vogt, and Haeckel, in their attempts to support the theory of the animal origin of man, had not sufficient knowledge of the embryology of monkeys. It is only recently that important work on this subject has been published.... The placenta often gives information of great importance in the classification of mammals. It is sufficient to glance at the zonary placenta of dogs and seals to be convinced of the relationship of these two species which at first sight seem so different. Now, the placentas of all the anthropoid apes examined up to the present are of the same discoid type as that of man. The arrangement of the umbilical cord of man, which was formerly considered as quite peculiar to him, is found in anthropoid apes, as has been established by Deniker and Selenka. It is striking that the anthropoids resemble man rather than the lower monkeys in the relation of the foetus to the foetal membranes. With regard to the embryos themselves, the similarity between those of monkeys and man is very great.... The youngest stages of human development that have been obtained can hardly be distinguished from those of the lower monkeys either in position or shape. More advanced stages exhibit greater differentiation, and the later embryos of man resemble those of anthropoids much more closely than those of the lower monkeys. The resemblance between the nearly mature foetus of anthropoids and human embryos of about the sixth month is evident enough." [169]