dieitely in front of the clcacal cavity, and snows 

 the extensions of tne peribranchial cavity on both 

 sides. The section passes through the extreme 

 posterior end of the dorsal tube. Fig. 16, line 



d, passes through the anterior ena of the cloacal 

 cavity, '/nich is seen to con?;oct the lateral por- 

 tions of the peribrancnial cavity. Fi^:. l^, line 



e, is taken from the posterior end of the bud, and 

 shows the connection of the left peribranchial cav- 

 ity v^ith the stolonic partition. The pericardial- 

 sac is also shown in this region. Fig. lo, line 



f, snows the undivided extreme posterior end of the 

 branchial sac. The section passes througn tno ai- 

 lated portion of the digestivF tract, the stomach, 

 and behind the connection '-rith the stolonic parti- 

 tion. All are drawn with D, 2. 



Figs. 19-21. Series of transverse sections of a bud of 



about the same age as the one represented in Fig. 

 5. Fig. 19, is a section through the anterior re- 

 gion, and shov/s the extensions of the peribranchial 

 cavity. Fig. 20, is dravm from a section .vhich is 

 taken from the middle region of the bud, and shows 

 the median portion or cloaca connecting the lateral 

 sacs of the peribranchial cavity, which is nov/ en- 

 tirely cut off from, the branchial sac. Fig. 21, 

 sho\'/s the posterior extensions (epicardial sacs?) 

 of the peribranchial cavity, and the remnant of the 



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