204 A HISTORY OF BIRDS 



of many links in the chain of evidence showing that the two 

 groups are really very intimately related indeed. 



With the exception of the Jacanas these eggs are all spotted 

 with various shades of brown and black on a groundwork vary- 

 ing in hue from white, cream, brown, to blue and green. The 

 Jacanas are remarkable. The Pheasant-tailed Jacana {Hydro- 

 pJiasianus chirurgiis) is the only species of the group which lays a 

 white egg ; while the remainder have the shell covered with in- 

 extricably twisted lines forming a sort of tangled meshwork all 

 over the o.^'g. 



But in the matter of variability none can compare with the 

 eggs of the Guillemot ( Uria troile), which are often of extreme 

 beauty. No less than thirty well-marked variations of these 

 eggs are exhibited in a special show-case at the British 

 Museum of Natural History. The great range in pigmentation 

 is really wonderful, but still more wonderful is the variability of 

 the size and distribution and shape of the markings. No mere 

 description could do justice to these eggs ; suffice it to say in the 

 ground colour they may be white, blue, green, brown, yellow, 

 buff or pink, while the markings consist of blotches, spots, 

 streaks and lines of every conceivable shape, and ranging 

 in colour through different shades of brown, reddish, choco- 

 late, and black ; while some eggs have scarcely any markings 

 at all, others have the surface of the shell thickly covered. 

 But there can be no doubt but that, as in other cases, the eggs 

 laid in successive seasons by each individual are always of the 

 same type, i.e., a Guillemot which lays a green or a red egg 

 for the first time of laying, will produce eggs of the same type 

 in successive years so long as it lives. 



The significance of such extreme variability is far from ap- 

 parent, but it has been suggested that this individuality is the 

 outcome of selection, the end gained being to enable each bird 

 in the colony — for these are social birds — to recognise its own 



The remarkable pyriform shape of the Guillemot's egg we 

 have already referred to ; the Lapwing and many other Plovers 

 lay eggs of a similar shape. On the other hand, no inconsider- 

 able number lay eggs of the more typical form. Even among 

 birds of the same genus and even of the same species great 

 differences in this respect obtain. Among the Snipe many 



