In anthropoids the lower segment of the lumbar vertebral column is deeply sunk between the high, wide, and flattened ilia, which converge closely towards the vertebral column. In man these bones are not so much higher than the base of the sacrum, and their crests diverge more widely from the vertebral column. In the large apes the lateral masses of the sacrum are comparatively deeply set below their anchylosis with the pelvic bones. In an aged male gorilla, for instance, the transverse processes of the two lower lumbar vertebræ often extend to the hinder borders of the ilia, although the second of the lower lumbar vertebræ is somewhat higher than the top of the crest of the ilium. This is still more remarkably the case in an old male chimpanzee, in which the lowest lumbar vertebra seems to be wedged in between the two ilia. In a young male chimpanzee, and in the adult female, both the lower lumbar vertebræ are almost compressed between the upper segments of the ilia. In the orang the lowest lumbar vertebra is placed between the ilia. Out of the five sacral vertebræ the first and second are articulated with these bones. In the gorilla the highest sacral vertebra, the twenty-fifth of the series, is the _fulcralis_. In this animal the first to the third sacral vertebræ form part of the connection with the crests of the ilia. In the chimpanzee the twenty-fifth is also the _vertebra fulcralis_, and from the first to the third are likewise connected with the ilia, but the third only to a limited extent; and in young males and in old females the connection is generally confined to the first and second sacral vertebræ. In the orang-utan the twenty-fourth vertebra is generally the _fulcralis_. In the gibbon the twenty-fifth vertebra is usually the _fulcralis_. In the siamang I found that the fifth of the five lumbar vertebræ was between the ilia. Out of the five sacral vertebræ the first and second were articulated with the said pelvic bones. In _Hylobates agilis_ the fifth and sixth of the six lumbar vertebræ were between the ilia, and the first and second of the five sacral bones were articulated with these. In the vertebral columns of the gorilla, the chimpanzee, and the orang we may observe an inconsiderable forward projection between the penultimate cervical and the second and third dorsal vertebræ. In the region below the second lumbar vertebra a similar forward projection may sometimes be observed. The so-called promontory at the entrance of the pelvis, that is, in the region developed between the lumbar and sacral vertebræ, which is remarkable in man, is only faintly apparent in anthropoids. The vertebral column is arched behind, since there is a dorsal curvature (see Figs. 17 and 23).