DEVELOPMENT OF THE COMMON FROG. 95 



circulation in them was clearly seen. There was no ap- 

 pearance of eyes. 



19. The head appeared much more formed, and frog-like 

 in shape. The eyes were distinctly seen ; but they were 

 covered by the ordinary skin. The gills had shrunk a 

 little; and they were darker-coloured, with much black pig- 

 ment ; but the circulation could be seen. 



19 (2). A tadpole was taken from the basin and killed 

 in sherry and water. A drawing was made of the under 

 surface of the body, showing the large mouth with thick 

 fleshy lips, and a little behind it a pair of suckers. They 

 were comma-shaped, with raised walls, and were joined 

 behind by a slightly raised curved line, the remains of the 

 posterior wall of the original single sucker. The opercular 

 fold closely resembled the gill-cover of fishes ; the gills 

 were rather large; and in what might be called (comparing 

 them to arms) the axilla was a double or treble row of 

 small rounded bodies like beads, the first noted appearance 

 of the internal gills. 



Plate VI. 



A tadpole which was taken from the basin as soon as 

 it was hatched, and had since been kept in a watch-glass 

 with water, was killed in sherry and examined. It was 

 slightly distorted, but not spoiled. Two drawings were 

 made — one of the upper, the other of the lower surface. 



20. The upper view showed nothing not previously 

 noted, except that the shape of the head was more decided, 

 as if the skull had advanced in development. The eyes 

 appeared, but were still covered by the ordinary skin ; 

 they were opaque white in the dead specimen. 



20 (2) . The lower view showed the large open mouth 

 with thick fleshy lips, and a horny sheath on the upper 

 jaw. The two suckers were shown as before, but a little 

 wider apart behind, and the curved line joining them was 



