Introduction to Animal Morphology. 97 



manubrium, but retaining its veil. The cavity of the 

 bell (nectosac) is lined by a muscular lamina, and 

 the pedicle of the nectocalyx has in it a process of 

 the body cavity, branching into four or eight necto- 

 calycine canals (like the gastro-vascular canals of a 

 gonophore). Between the proximal nectocalyces is a 

 groove (hydroecium) for the proximal end of the 

 coenosarc, within which it can be wholly or partially 

 retracted. The coenosarc is flexible, unbranched, con- 

 tractile, filiform, never invested by a periderm. The 

 proximal end of the somatic cavity dilates in front of 

 the nectocalyces into a variously shaped cavity 

 (somatocyst), ciliated within, containing large, re- 

 fracting globules, often air bubbles, and a vacuolated 

 endoderm, often nearly closing the cavity. Each 

 polypite has a narrow peduncle (proximal part), and- 

 consists of a wide, gastric portion, ciliated and villous 

 within, at whose opening into the peduncle there is 

 an endodermal fold (pyloric valve). The distal end of 

 each polypite is the hypostome. Coloured hepatic 

 cells may line part of the gastric wall (Praya), and 

 cnidae exist among the villi of the endoderm. The 

 single so-called tentacle of each polypite arises from 

 the peduncle, and is a modified zooid consisting of a 

 slender basal " pedicle," a middle thick part or " sac- 

 culus," the equivalent of the manubrium, armed with 

 cnidae, and a terminal, often coiled, "filament." The 

 pedicle may expand where it joins the sacculus, and 

 when this dilatation encloses the base of the second 

 part it is called the involucre, and is a modified 

 medusa bell. A muscular angle-band {^Leitckart), 

 folded in zigzags, lies on the hinder wall of the sac- 

 culus ; its proximal end passes into the pedicle, its 



distal into the filament. The peduncle of the polypite 



H 



