Mucous Membrane in the Human Embryo. 559 
11. Duodenal glands originate as outgrowths from the intes- 
tinal glands. They branch repeatedly and the branches of each 
become arranged in groups. They were first observed in an em- 
bryo of 78 mm. 
12. Circular folds of the mucous membrane make their ap- 
pearance in the mid region of the small intestine at 73-78 mm. 
They become more numerous, more regularly placed, and taller 
in the older stages. 
