at 



tail 



Fig. 453. — Illustrating the metamorphosis of the tadpole of Qiona intestinalis. 

 (After Willey.) 



A, young tadpole just after fixation, seen from the right side — the mouth is still in the larval position 

 and the tail is just beginning to degenerate. B, young fixed dona, in which the mouth is rotated up- 

 wards and the tail is reduced to agranular mass. C, young fixed Cionaj in which the mouth has attained 

 the upper pole of the animal and inwhich the tail has disappeared, a, anus ; at, atrial canal ; b.v, 

 brain-vesicle ; endst, endostyle ; gatig.ad, adult ganglion ; gr.si-^, the first four gill-slits ; hyp, hypophysial 

 canal ; int, intestine ; m, mouth ; mn, chin (mental ;process) ; to.c, nerve cord ; n.t, nerve tube ; oes, 

 oesophagus ; pCy pericardial sac ; pph, peripharyngeal ciliatg4 band ; py.g, pyloric gland ; st, stomach. 



m 



