72 BIOLOGY 



But it is among the animals that the care of offspring 

 is most highly developed. This may be due to the more 

 hazardous life they lead. We cannot say in what forms 

 parental care first appeared, nor does our ignorance 

 matter much, for it is latent in all. It is as well deve- 

 loped in the lower as in the higher types, but it is more 

 commonly ascribed to the higher types as they come 

 more readily under our notice. Numerous examples 

 could be cited, all equally interesting. We might men- 

 tion the case of the leech and the jelly-fish, the frog and 

 the crocodile, the spider and the insect, but we must be 

 content with a few examples only. 



Numerous fishes build nests in which the eggs are 

 laid, and immediately after the deposition of the eggs 

 the male mounts guard and keep all intruders away. 

 This type is shown in a remarkable degree by the stickle- 

 Back. Other fish carry their eggs in their mouths, as in 

 the case of Arius, or as in the case of the sea-horse, in 

 some specialised portion of the body till they hatch out. 

 Among amphibians, parental care is even more highly 

 developed. The obstetric frog winds the new-laid eggs 

 round his hind-limbs and retires into some hole where 

 he remains looking after them, and only comes out at 

 night-fall to look for food ; a walk which some assert 

 has its main purpose not to seek food, but to acquire 

 sufficient moisture for the developing eggs. Even more 

 interesting are the means adopted by some frogs, where 

 the eggs are placed in a pouch-like depression in the 

 skin of the back and carried there till they are able to 

 fend for themselves. Quaintest of all is the case of the 

 male Chilian frog, which carries the eggs and the young 



