The figures on Plate I are designed to show diagrammatically the relations of the caudal end of the spinal cord and the vertebral 

 column in a series of human erahryos varying from 4 mm. to 67 mm. long, and are so arranged that the segmental levels, as 

 indicated at the left, correspond throughout, the thirty-fourth segment being emphasized by a heavy line. In the two younger 

 stages the segments were detennined by the myotomes; the remainder were determined by the sclerotomes, or the bodies of the 

 vertebrte. In making the diagram it was found necessary to make all the segments of the same width; in reality the more 

 caudal ones are relatively much narrower. Also, the individual segments become wider in the older stages, whereas in the 

 diagram they are kept at the same width. There is thus introduced an axial distortion which should be kept in mind in 

 studying the figures. In figures 1 to 15 the surface profile of the caudal region is indicated and the cloacal membrane is 

 shown by a wider Hue. In figures 1 to 5 the caudal gut is shown by a broken Une. In figures 4 and 5 it will be noted that a 

 remnant of the gut is still present, though its communication with the cloaca is interrupted. Early stages in the formation of 

 the filum t«rminale are shown in figures 25 to 30. The figures in this plate are all based upon profile reconstructions made 

 from the following embryos: 



