CONCERNING TADPOLES 193 



not surrounded b/ a layer of black pigment ; and this 

 because they are excluded from the sun's rays and hence 

 the pigment, which serves at once as a screen from ex- 

 cessive light, and to attract heat, is useless. 



The " Wollunnkukk " (Phyllomedus-a hypochondrialis) of 

 Paraguay furnishes an even more extraordinary instance 

 of nursery building, discovered during the exploration of 

 the Paraguayan Chaco by Dr. Budgett. While sitting 

 near the water's edge he saw a female carrying a male upon 

 her back. At last she climbed up the stem of a_ plant, 

 reached out and caught hold of the tip of an overhanging 

 leaf, and climbed on to it. Both then caught hold of its 

 edges and held them together ; and into the funnel thus 

 formed the female poured her eggs, the male fertilising 

 them as they passed. The jelly surrounding the eggs 

 served as a cement to hold the edges of the leaf together. 

 Then, moving up a little further, the process was repeated 

 until the leaf was full, ^nd about a hundred eggs had been 

 enclosed. 



The eggs are peculiar in that they contain much food- 

 yolk surrounded by a quantity of jelly which soon becomes 

 fluid, so that the embryo is seen floating within a glassy 

 capsule. Herein the larval life is also passed, and from 

 the absence of pigment from the skin the external gills 

 assume a crimson colour, imparting to the egg at this stage 

 a singularly beautiful appearance. In due course the 

 tadpole stage is reached. And a most wonderful tadpole it 

 is. At first, transparent as glass, the only conspicuous 

 feature is the eye, which is of a bright metallic green, so 

 that when swimming these jewel-like discs and a bright 

 metallic green spot between the nostrils are all that can 

 be seen. Soon, however, the hind-legs appear. This is 

 the signal for a further astonishing change. The glassy 

 13 



