cloacal and the lateral divisions of the peribranchial cavi- 

 ty. This is essentially the same process as that which Pi- 

 zon (22) and Hjort (8) have described for Botryllus . 



In Perophora the folds which separate the peribran- 

 chial cavity from the inner vesicle, do not involve the en- 

 tire length of the latter, but leave nearly the whole of the 

 anterior half undivided, as well as a short region at the 

 posterior end of the vesicle. And further, the whole peri- 

 branchial cavity is not constricted off at the same tir.e, but 

 as stated above, the furrows begin anteriorly and extend 

 gradually back, so that at any given stage the opening of the 

 median vesicle into the peribranchial cavity is much wider in 

 a posterior section than in one further forward. 



V^hen the right peribranchial cavities are being 

 separated off, as just described, a broad pouch or divesti- 

 culum grov/s out from the anterior margin of each, and by de- 

 grees spreads over the undivided portion of the inner vesi- 

 cle. These pouches are direct continuations of the lateral 

 Cavities, and later completely cover the sides of the ante- 

 rior region of the peribranchial sac, but they never fuse 

 dorsally. 



Similar extensions are carried out from the poste- 

 rior margin of the lateral cavities, and though not promi- 

 nent at first, still, as the bud gets older and increases in 

 length, they attain a considerable size and surround a part 

 of the digestive tract. 



The peribranchial cavity nov/ consists of two deep 



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