Fig. 186—Human ovum of twelve to thirteen days (?). (From Allen Thomson.) 1. Not opened. 2. Opened and magnified. Within the outer chorion the tiny curved fœtus lies on the large embryonic vesicle, to the left above.
Fig. 187—Human ovum of ten days. (From Allen Thomson.) Opened; the small fœtus in the right half, above.
Fig. 188—Human fœtus of ten days, taken from the preceding ovum, magnified, a yelk-sac, b neck (the medullary groove already closed), c head (with open medullary groove), d hind part (with open medullary groove), e a shred of the amnion.
Fig. 189—Human ovum of twenty to twenty-two days. (From Allen Thomson.) Opened. The chorion forms a spacious vesicle, to the inner wall of which the small fœtus (to the right above) is attached by a short umbilical cord.
Fig. 190—Human fœtus of twenty to twenty-two days, taken from the preceding ovum, magnified. a amnion, b yelk-sac, c lower-jaw process of the first gill-arch, d upper-jaw process of same, e second gill-arch (two smaller ones behind). Three gill-clefts are clearly seen. f rudimentary fore-leg, g auditory vesicle, h eye, i heart.
In the opinion of some travellers and anthropologists, the atavistic tail-formation is hereditary in certain isolated tribes (especially in south-eastern Asia and the archipelago), so that we might speak of a special race or “species” of tailed men (Homo caudatus). Bartels has “no doubt that these tailed men will be discovered in the advance of our geographical and ethnographical knowledge of the lands in question” (Archiv für Anthropologie, Band XV, p. 129).