122 DR. THOMAS ALCOCK ON THE 



had attained a considerable size, and had each the form of 

 a sacculated tube, bluntly pointed at their free end. 

 During this period the liver increases much in size, and 

 additional lobes are formed. 



Fifth Period. — The last period of the aquatic life of the 

 frog extends, according to the present observations, from 

 the seventy-fourth to the eighty-third day, at which time 

 the animal has left the water and attained the perfect form 

 of the adult. At the commencement of this period it is a 

 tadpole, with a large powerful tail, a pair of large hind 

 legs with webbed feet, and a pair of equally developed fore 

 legs still retained beneath the opercular fold which forms 

 the gill-chamber. The gills are still in action ; and the 

 opening at the left side remains for the discharge of 

 water. 



Now, however, the animal ceases entirely to feed, and 

 the alimentary canal soon becomes empty; the large white 

 frilled lips shrink, and the sets of small teeth upon them 

 degenerate and drop off ; the horny beaks disappear ; the 

 mouth widens ; the new lips consist of ordinary skin ; and 

 the large fleshy bifurcated tongue of the frog is formed. 

 At the same time the intestine shrinks both in length and 

 diameter, especially at the part which forms the centre of 

 the coil ; soon afterwards its upper part begins to be dilated 

 to form the stomach ; and the remainder becomes rapidly 

 smaller and shorter as the stomach enlarges, until it con- 

 sists of a small and slender gut, making only two or three 

 short turns below the stomach at the left side. The liver 

 at the same time enlarges ; and the gall-bladder is seen, 

 very large and filled with dark green bile. 



When these changes in the alimentary apparatus have 

 been partly accomplished, the fore legs are pushed out, 

 the action being instantaneous for each limb. Sometimes 

 the right, sometimes the left comes out first ; and the left 



