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rOPULAR SCIENCE MONTHLY 



Stretching out and closing the toes, she mixes the sticky mass with 

 air and breaks the big bubbles up into smaller and smaller foam. Sim- 

 ilar movements of the feet of the male drive the mass backward and 

 leave the eggs more free for the fertilization that follows. When the 

 eggs have been fertilized and provided with a protecting and aerating 

 mass, the parents break out from the nest and take up their life 

 amongst the trees. The foam mass meanwhile gradually becomes 

 liquid, and flowing out through the hole the parents left on leaving the 

 nest, carries the young into the outside water. 



Very different is the nest made by another tree-frog in Brazil, The 

 quaint, beaver-like activities of this creature (Hyla faher) are described 

 by one who observed them in his own garden. On a moonlight night 

 one may see a slight movement of the water as if something were moving 

 under it. Then a little mud rises, shoved up by a tree-frog — but only 

 the hands of this are visible. It dives down and again brings up mud; 



Fig. 4. 



gradually the accumulated mud seems a little wall, and eventually it 

 rises 10 cm. above the water and extends as a ring a foot in diameter. 

 Such atolls of mud are shown in Fig. 4. They form little circular 

 dikes of mud elevated above the general expanse of water. The making 

 of them is by no means a matter of chance. The frog — and it is the 

 female that labors, in full enjoyment of her 'rights,' while the male 

 rides passively — uses lier liands to compress and to smooth the inside 

 of the wall in a most remarkable way. The top also of the miniature 

 fortress is carefully vianipulated, the frog crawling out of the water 

 to make all the structure solid and smooth, all but the outer escarp- 

 ment, which is left rough. 



The frog makes the bottom of the crater-like cavity, under water, 

 pmooth by gliding along it on its belly, and also by spreading out its 

 hands over it. During all this work the frogs make no sound, though 

 near at hand isolated males may be heard calling their mates. 



In this circular nest the spawn is deposited, but not till four or 



