66 



ADAM SEDGWICK. 



The tubules of the Wolffian body do not develop ^rom 

 serial involutions of the peritoneal epithelium, hut from the 

 cells of the intermediate cell mass. The intermediate cell 

 mass is so familiar to all students of Avian embryology that 



Fig. 1.^ — Section from a chick of the second day, showing the inter- 

 mediate cell-mass, M. c. Medullary canal. P. v. Protovertebra. 

 W. d. Wolffian duct. p. p. Body-cavity, c. h. Notochord. a. o. aorta. 



* For the woodcuts, figs. 1 and 2, I have to thank Mr. Balfour. Fig. 1 

 is from the ' Elements of Embryology.' 



