dorsal connecting piece or cloaca; this condition appears in 

 Pig, 20. Beyond the cloaca, the posterior pouches of the 

 lateral sacs, which like the anterior pouches are not united 

 dorsally, are seen in Fig. 21; the connection of the left 

 sac witn the stolonic partition in tnis figure has already 

 been referred to. By this time the process of displacement 

 is completed, and the definitive syminetrical arrangement of 

 the pharynx and peribranchial cavity is reached. The con- 

 nection between the left peribranchial sac and tae partition 

 of the stolon is nearly severed; it is found in only two 

 sections of this series, one of which is seen in Fig. 21. 

 A total preparation of a bud at about this stage is shown in 

 Pig. 5. 



Epicardiam. This structure was first described 

 by Van Beneden and Julin (33) in the buds and larvae of 

 Clav elina, and was shown by these authors to be closely con- 

 nected with the development of the pericardimi. It arises 

 as an evagination of the posterior wall of the branchial sac, 

 and a little further back divides into two blind pouches, 

 which remain separate in the buds, but in the embryo unite to 

 form the "cul de sac epicardique" of Van Beneden and Julin; 

 the latter is continued into the stolon to form the double- 

 walled partition. The development of the epicardium will be 

 again referred to in connection with the pericardimn, with 

 which it stands in very close relation in some Ascidians. 



In Dis taplia Salensky (27) has described the epi- 

 cardial sacs as arising in the buds at an early stage by eva- 



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