130 The Field Naturalist's Quarterly May 



a rudder only. Our guillemots and razorbills also make 

 great use of their wings when under water, and they, too, 

 make practically no nest. The least highly developed bird 

 which lays a highly coloured egg is the tinamou. Pro- 

 fessor Newton says : " They are remarkable objects, curi- 

 ously unlike those of any other bird ; their shell looks as 

 if it were of highly burnished metal, or glazed porcelain, 

 presenting also various colours, from pale primrose to light 

 indigo, or from chocolate-brown to pinkish-orange. In form 

 they are more or less globular and completely opaque." 

 Thus birds so low in the scale of organisation as ostriches, 

 emus, cassowaries, penguins, and tinamous lay eggs varying 

 in number from one to many, globular or elliptic in shape, 

 white or whole coloured, and with rough or highly polished 

 shells. 



If we compare these facts concerning the life-history 

 of birds with some of the characteristics of the eggs and 

 nesting habits of reptiles, we cannot help noticing how 

 nearly they correspond. As we said before, practically all 

 reptiles' eggs are white or dingy yellow. Marine tortoises 

 lay globular eggs — a few elliptic ; land tortoises lay very 

 few eggs, crocodiles very many. Neither tortoises nor 

 lizards incubate, but some of the latter are ovo-viviparous. 

 Pythons coil round their eggs to hatch them. The alli- 

 gator nests like the megapodes. Here, then, we see 

 numerous traits in which both the shape and colour and 

 number of eggs, the nesting and incubation, of reptiles 

 and birds approximate very closely. We have seen how 

 crocodile-like are the nesting habits of the megapodes, 

 and how reptilian are many of the eggs of the lower 

 forms of present-day bird-life, — the eggs of the crocodile 

 being enclosed in a calcareous shell and laid in holes made 

 in the sand or mud of the river-side, where they are left 

 to be hatched by the heat of the sun ; or, as is the case 

 with some American species, deposited in hillocks which 

 the reptiles raise for themselves and hollow out, filling 

 the cavity with leaves, when the eggs deposited therein 

 are hatched by the heat generated by the decomposing 

 mass, — one great crested grebe still making, as before 

 mentioned, a modified use of the same expedient. We 



