NOTES ON BATRAOHIANS OF THE PARAGUAYAN OH AGO. 317 



There is a conspicuous absence of pigment for some time over 

 the pineal body (fig. 26). 



Black pigment appears first, then green. At the end of 

 about five more weeks the tadpole has begun to develop its 

 hind limbs. During this period it has grown to a length of 

 8 cm. The upper surfaces are now a glossy green, beneath 

 silver and rosy ; the tail is still transparent, and the red blood- 

 vessels give it a bright red colour (fig. 31). 



At the time of the development of the hind limbs there is a 

 very great accumulation of black pigment at the middle of the 

 tail, especially below (fig. 31). 



The tail is absorbed very rapidly up to this point ; the final 

 absorption of the proximal part of the tail is postponed for 

 some days. 



The young frog, having now grown both pairs of legs, leaves 

 the water and betakes itself to the blades of grass close by 

 (fig. 32). 



Here it sits during the time of absorption of the remainder 

 of the tail. When lying in the blade of grass, only the bril- 

 liant green upper surfaces are visible, and the tail helps to 

 make the young frog still less noticeable by shading off" the 

 body, and causing it to become merged in the green of the 

 grass blade. 



The young frog at the close of its metamorphosis is two 

 thirds the length of the adult frog, and at this time acquires 

 the red flanks barred with black (fig. 33). 



There is a certain stage in the life of this larva when it will 

 not bear transferring from the pool to aquaria. If the larvae 

 are transferred at the time when pigment in the tail is just 

 beginning to accumulate, that is when they are 3 cm. in 

 length, they invariably die, though both younger and older 

 larvae stand the change quite well. 



Development. 



External Characters. — Segmentation is holoblastic, 

 though not so regular as in Rana and most Batrachia (figs. 



