METAMORPHOSIS. 



97 



of the alimentary canal, the oesophagus and the hind-gut, now lie 

 almost horizontally. 



While the intestine has shifted in the way just described, the 

 vestibule has considerably lengthened (Fig. 46 B). At a later stage 

 only a part of this cavity is retained, the lower part, lying in the 

 peduncle, disintegrating through histolysis of its walls. Further 

 disintegration and histolysis take place also in other parts of the 



Fig. 46.— Three stages in the metamorphosis of Pedicellina (after Harmer). J, larva just 

 attached. B, commencement of the rotation of the alimentary canal, and partial disintegra- 

 tion of the organs. C, the breaking through of the vestibular aperture and the development 

 of the tentacles (t). a, anal aperture ; d, dorsal organ ; m, oral aperture ; p, pedal gland ; 

 (, rudiments of tentacles ; lu, ciliated disc (sucker of Harmer). 



vestibule and of the intestinal wall. These broken down cell-masses 

 are found in numbers in the lumen of the vestibule and in the 

 stomach. These processes, however, do not here lead to the 

 destruction of the whole organ, but only affect the portion nearest 

 the peduncle. The two larval organs, the dorsal organ (d) and the 

 ciliated disc (w), on the contrary, are completely destroyed. 



After the rotation of the intestinal canal round its transverse axis, 



