Care of the Young in the Animal Kingdom. 149 



in anthropomorphic language, goes without saying.^ 

 Some instances of taking care of the young occur also 

 among amphibias. The female of the Surinam toad 

 (Pipa dorsigera) carries her young in the cavities of 

 her dorsal skin; whereas in a frog species (Arthro- 

 leptis seychellensis) inhabiting Central America the 

 young hold on to the back of the male.^ But quite 

 universal and commonly known is the care bestowed 

 by birds and mammals upon their young. Yet its 

 highest perfection, connected with the most perfect 

 form of community life in the animal kingdom, does 

 not occur with the higher mammals, but with the 

 social insects, in particular with ants. Here this degree 

 of perfection is made possible by the organic division 

 of the female sex into females proper and into nurses 

 (workers) incapable of generation. And although 

 these are not the mothers of the children they nurse, 

 the psychic development of their breeding instinct 

 reaches the greatest perfection in the whole animal 

 kingdom. Before discussing, however, this aspect of 

 the breeding instinct of ants, we must first explain its 

 connection with the laws of their organic develop- 

 ment. 



The bodily differentiation of the members of an 

 insect-state into classes and castes, their co-habitation 

 in a common abode, their nest-construction, acquisition 



*) The following amusing quotation will do for the purpose: "The 

 greatest danger threatens him (Mr. Stickleback) from the mothers of 

 his own children. Eager to devour their own offspring, they are con- 

 tinually dashing in unison against the nest, in which the young are 

 guarded by their watchful father, and but too often the latter pays the 

 penalty of his polygamy" (Thilo, "Umbildungen an den Gliedmassen der 

 Fische," in "Biolog. Centralbl.," 1897, 1st issue, p. 24). 



2) "Zoolog. Jahrb. Abth. fuer Systematik," XII (1898), 89 ff. 



