6 



PHYLUM TUNICATA (UROCHORDA) 



a/fine, the duct of the neural gland. The walls of the pit 

 are innervated by nerve fibres from the ganglion, and some of 

 its lining cells appear to be sensory. The subneural gland, the 



FIG. 4. Inner surface of buccal cavity and of the anterior part of the pharynx of dona, 

 a prebranchial zone ; b tentacular circlet ; c peripharyngeal band ; d epibranchial groove : 

 e union of endostyle with peripharyngeal band ; / endostyle ; g pharyngeal apertures ; h dorsal 

 lamina with languets ; i subneural gland ; i' dorsal tubercle ; k longitudinal muscle (after 

 Vogt and Yung). 



duct of which is lined by cubical non-ciliated cells, is in close 

 contact with the ganglion, generally on its ventral side, but it 

 sometimes lies dorsal to the ganglion (Cynthia, Molgula, Botryllus, 

 etc.). 



FIG." 5. Diagrammatic longitudinal section through the ganglion and subneural gland of 

 Clavelina (after Seeliger from Bronn). ec ectoderm ; en endoderm ; fb peripharyngeal 

 band (not grooved in this form) ; 1g ciliated pit (dorsal tubercle); g ganglion; n nerve; p 

 atrial cavity ; sd subneural gland. 



The prebranchial zone is in some forms covered with small papilliform 

 projections. The opening of the ciliated funnel varies much in form. 

 In a few cases it is circular. More often it is semicircular or horseshoe 

 shaped (Fig. 4). Sometimes the horns of the semicircle are spirally curved 



