218 ORGANIC EVOLUTION CONSIDERED 



Many instances besides those already referred to, 

 of instincts and of peculiarities of structure adapted 

 to the instincts — cases in which the one would be use- 

 less without the other — exist. The Surinam Toad is 

 a strange example. With regard to it I quote from 

 J. Gr. Wood's Natural History. " When the eggs are 

 laid, the male takes them in his broad paws, and con- 

 trives to place them on the back of his mate, where 

 they adhere by means of a certain glutinous secretion, 

 and by degrees become embedded in a series of curi- 

 ous cells formed for them in the skin. When the 

 process is completed, the cells are closed by a kind of 

 membrane, and the back of the female Toad bears a 

 strong resemblance to a piece of dark honey-comb, 

 when the cells are filled and closed. Here the eggs 

 are hatched, and in these strange receptacles the 

 young pass through their first stages of life, not ' 

 emerging until they have attained their limbs and can 

 move about on the ground. 



"After the whole brood have left their mother's 

 back the cells begin to fill up again, closing from be- 

 low as well as from above, and becoming irregularly 

 puckered on the floors. The cells in the middle of 

 the back are the first to be developed; the whole 

 process occupies rather more than eighty days." 



In this instance the instinct of the male causing 

 him to place the eggs on the back of the female, the 

 instinct of the female which causes her to keep the 

 eggs on her back, as if she knows that their presence 

 there is necessary for their development, the forma- 

 tion of the cells in the skin of her back, and the 

 changes in the mode of life of the young frogs with- 

 out destroying them must be accounted for. All of 

 these changes must have occurred simultaneously,, 

 otherwise this method of developing the young could 

 not have originated. To my mind it is impossible t;> 



