247 
into the folds of the epithelium, I have not considered it because in 
many of the sections the epithelium is separated from the underlying 
tissue. Folds of this part are produced by the hardening reagent 
used. To determine whether the appearance shown in Fig. 3 is due 
to the sections passing through longitudinal folds or to villi, a recon- 
struction in wax was made of a portion of the intestine, which showed 
definitely that there were slight longitudinal folds but no villi present. 
Embryo XLV. The sections of the intestine show that the folds 
already present in VI are greatly increased. The section, Fig. 4, also 
shows that the cone of the folds 
is markedly increased. A recon- 
struction of a block of this in- 
testine is shown in Fig. 5. The 
longitudinal folds are much more 
marked than those found in em- 
bryo VI. These folds are now 
irregular, showing indications of 
transverse furrows, as if the longi- 
tudinal folds were about to break 
up into blocks or villi. 
Embryo XXXIV. The appear- 
ance of a section through the 
jejunum of this embryo shows the 
presence of villi, which are very 
pronounced in the reconstruction, 
Fig. 6. In this reconstruction only 
Fig. 4, Section of the intestine of a human embryo (XLV) 28 mm long, multi- 
plied 85 times, 
Fig. 5. Reconstruction of a piece of the intestine of a human embryo (XLV) 28 mm 
long, multiplied 85 times, 
