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peritoneal cavity. They extend between the proventriculus and 

 the lungs, as shown in Fig. i, G. D. On account of their 

 location, I shall speak of these sacs as the gastric diverticula. 1 

 From the one on the right side the lesser peritoneal cavity of 

 birds and mammals develops. 



A few hours later, eighty-eight hours, when the body is flexed 

 to its maximum, the gastric diverticula become more semicircu- 

 lar in transverse section, and also enclose the proventriculus 

 on either side. On the right side the diverticulum is larger, 

 markedly cup-shaped, and connects by means of a narrowed 

 opening with the right pleuro-peritoneal cavity (Fig. 2, F. IV.). 2 



P. P 



R.G.D. 



F. W. 



Fig. 2. Corrosion preparation of the right gastric diverticulum of a chick, 88 

 hours. Enlarged 44 diameters. P.P., pleuro-peritoneal cavity; R.G.D., right 

 gastric diverticulum; F. IV., foramen of Winslow; L., position of the right lung. 



In this embryo the liver lies between the heart and proventric- 

 ulus, the opening lying to the oral and dorsal side of the liver. 

 The cceliac axis is already formed, and the gastric and hepatic arte- 

 ries pass directly to the proventriculus and liver. On account 



1 Earlier stages are shown in Duval, PI. XXV, Figs. 404 and 405. His sections 

 are viewed from the aboral side. The communication with the pleuro-peritoneal cavity 

 of the stage which I represent in Fig. 1, he shows on PI. XXX, Figs. 473 to 476. 



2 Duval, PI. XXX, Figs. 375, 376, shows a section of the communication of this 

 opening with the ccelom. 



