118 THE STUDY OF ANIMAL LIFE CHAP. 



grows forwards and downwards. Just before the hook- 

 process becomes an "eye," the double bunch of eggs is 

 in some way or other slipped in ; as the " eye " is com- 

 pleted it is fixed ; and the male goes about with the 

 developing eggs 011 the top of his head. This case is 

 peculiarly interesting because the two adaptations, which 

 so perfectly fit, are, as it were, very far apart the fila- 

 ments round the eggs and the bony process on the male's 

 head. Of this the female shows no trace. 



Amphibians, like fishes, to which they are linked by 

 many ties, are either quaint or careless parents. Again, 

 the males assume the responsibilities of nurture. The 

 obstetric frog (Alytes obstetricans), common in some parts 

 of the Continent, takes the eggs from his mate, winds 

 them round his hind-legs, and retires into a hole, whence, 

 after a fortnight or so, he betakes himself to the water, 

 there to be relieved by the speedy hatching of his precious 

 burden. Even quainter is the habit of the male of a 

 Chilian frog (Rhinpderma darwini), who keeps the eggs 

 and the young in a ventral pouch (Fig. 35), turning a 

 resonating sac in a most matter-of-fact way into a cradle. 

 He is somewhat leaner after it is all over. It is inter- 

 esting to notice how similar forms and habits recur among 

 animals of different kinds, like the theme in some musical 

 compositions. The spiral form of shell common in the 

 simple chalk-forming Foraminifers recurs in the pearly 

 nautilus ; the eye of a fish is practically like that of 

 many a cuttle, though the two are made in quite different 

 ways ; and an extraordinary development of paternal 

 care may signalise animals so distinct as sea-spider, 

 stickleback, and frog. 



But we must not be unfair to the female amphibians. 

 Without doubt most of them are willing to be quickly 

 rid of their eggs or young, and as these are usually very 

 numerous, the mortality in the pools is of little moment. 

 In some cases, however, water-pools arc less available 

 than in Britain, and then we find adaptations securing 

 the welfare of the young. The black salamander of the 

 Alps, living at elevations where pools are rare, retains 

 her twin offspring until more than half of the tadpole life 



