THE FBOG AS FAEENT. 



71 



five days, as a rule, after the nest is completed; there is a period of rest 

 between the nest-making (which in one case required two successive 

 nights) and the egg-laying. The young hatch out as tadpoles and 

 continue to live in the narrow circle of home till the wall be broken 

 down by time and weather to set them free in the world. 



It is the habit of all these nest-makers to put their eggs into more 

 or less imperfect nests and then go off and leave them to their fate, 

 the nest, no doubt, increasing the chances of the young passing safely 

 through the earliest stages of infancy — which we all know is a critical 

 period for man or fish. Some other frogs have quite a different habit; 

 carrying their eggs about with them, and so giving them the benefit, 

 if not of actual defense against enemies, at least of passive protection, 

 in that the eggs thus have the same conditions of moisture and con- 

 cealment which they, the adults, need and obtain for themselves. Such 

 frogs we have called 'nurses.' 



Fig. 5. 



Fig. 6. 



Of these nurses the most often mentioned is the so-called 'obstet- 

 rical toad' found in Switzerland, France and western parts of Germany. 

 As shown in Fig. 5, the eggs are carried about attached to a band, 

 which is wrapped about the legs of its parent, but the parent who thua 

 carries the offspring about in the moist grass as it seeks food in the 

 evening is not, as one might expect, the mother, but the father toad. 



When the eggs are laid and fertilized, the male takes up his burden 

 and carries it till the young are ready to hatch, when he goes to the 

 water and lets the brood escape into the proper element. What leads 

 him there at the right time remains still to be found out. How he 

 comes to assume this care is also not clear; according to some accounts 

 the male, when upon the back of the female, seizes the egg-string first 

 with the right, then with the left foot, and wraps it in figure of eight 

 loops about its own legs. Others say that the male sits behind the 

 female, "with its back turned toward her, and as the eggs emerge, the 

 male seizes them between his ankles and, throwing himself now on his 

 back and now on his belly, turns over and over until the egg-string is 

 all drawn out and wrapped about his legs; hence the name Alytes obstet- 



