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distributed; at points, they are in clusters, Fig. 1 A and B. These 
observations regarding the form of the villi and their number shows 
that both old and young villi exist side by side, which proves that 
after the villi have once appeared in the intestine, their further growth 
in number is by the formation of new villi between the ones already 
existing. 
I now return to the formation of the villi in the human intestine. 
I will first describe the mucous membrane in each of the embryos 
given in the Table. 
Embryo IX. The lumen of the intestine is perfectly smooth, 
there being no indication of folds or villi in any part of it. There 
is present throughout the entire intestine a thickening of the epithelial 
covering as shown in Fig. 2, which is taken from the jejunum of this 
embryo. 
Fig. 2. Fig. 3. 
Fig. 2. Section of the intestine of a human embryo (IX) 17 mm long, multiplied 
85 times. 
Fig. 3. Section of the intestine of a human embryo (VI) 24 mm long, multiplied 
85 times. 
Embryo VI. Fig. 3 is from the upper part of the intestine of 
this embryo. There are small folds of the epithelial lining present, 
into which the underlying mesodermal tissue projects. It may be well 
to state that unless there is a projection of the subepithelial tissue 
