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BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



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thence into the common cloaca (fig. 3). On the ventral side of the 

 pharynx is the endostyle, extending nearly the whole length of the 

 branchial chamber. The endostyle in Pyrosoma does not differ 

 materially from that of other Tunicates. Peripharyngeal bands, 

 continuous with the ciliated ridges bordering the endostyle, pass 

 around the pharynx, immediately in front of the stigmata, uniting 



behind the ganglion. In the Py- 

 rosomata ambulata they come to- 

 gether at a broad angle imme- 

 diately under the ganglion (fig. 13, 

 pi. 22), but in the Pyrosomata 

 jixata they continue backward 

 nearly parallel to each other, one- 

 third to one-half of the distance 

 from the ganglion to the esopha- 

 geal aperture, where they come 

 together at a very sharp angle (fig. 

 5, pi. 17). At the point where 

 they unite the dorsal languets com- 

 mence, the latest formed of these 

 ,l r _ ' lying infront (fig. 7, pi. 18; fig. 17, 



i S.JT B i / f-V-v^V- pi. 23). The lateral ciliated cells 



of the endostyle are continued be- 

 hind onto the postero-ventral wall 

 of the pharynx as an indistinct 

 ciliated band which runs to the 

 opening of the esophagus. 



In each of the branchial lamellae 

 are a large number of stigmata 

 which lie in rows. These originate 

 from simple, elongated, trans- 

 verse gill slits such as are seen in 

 Doliolum. In Pyrosoma they are 

 divided very early by the growth, 

 across the inner surface of each 

 branchial lamella, of longitudinal 

 folds containing lymphatic liquid, 

 but apparently no corpuscles (Burghause, 1914). Thus the primi- 

 tive elongated slits are changed into a great number of secondary 

 stigmata which are oblong in shape. The stigmatal rows thus 

 formed do not always lie in a direction transverse (dorso-ventral) 

 to the zooid, but in the Pyrosomata Jixata they run obliquely from 

 the postero-dorsal to the antero-ventral part of the pharynx (fig. 8, 

 pi. 19). Each stigma is abundantly ciliated, as in other Tunicata. 

 Ordinarily the branchial lamellae are oval, elongated in the axis of 



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Fig. 3.— A diagrammatic frontal section 

 through a zoold, of the elongated type, 

 of Pyrosoma atlanticum. The actual 

 number of stigmata is much greater 

 than shown. after seeliger (1895). 



