CHAPTER XV 



ox THE SHAPES OF EGGS, AND OF CERTAIN OTHER 

 HOLLOW STRUCTURES 



The eggs of birds and all other hard-shelled eggs, such as those 

 of the tortoise and the crocodile, are simple solids of revolution; 

 but they differ greatly in form, according to the configuration of 

 the plane curve by the revolution of which the egg is, in a mathe- 

 matical, sense, generated. Some few eggs, such as those of the 

 owl, the penguin, or the tortoise, are spherical or very nearly so ; a 

 few more, such as the grebe's, the cormorant's or the pelican's, are 

 approximately elhpsoidal, with symmetrical or nearly symmetrical 

 ends, and somewhat similar are the so-called "cyhndrical" eggs 

 of the megapodes and the sand-grouse; the great majority, hke 

 the hen's egg, are ovoid, a Httle blunter at one end than the other ; 

 and some, by an exaggeration of this lack of antero-posterior 

 symmetry, are blunt at one end but characteristically pointed at 

 the other, as is the case with the eggs of the guillemot and puffin, 

 the sandpiper, plover and curlew. It is an obvious but by no 

 means negligible fact that the egg, while often pointed, is never 

 flattened or discoidal ; it is a prolate, but never an oblate, spheroid. 



The careful study and collection of birds' eggs would seem to 

 have begmi with the Count de Marsigh*, the same celebrated 

 naturahst who first studied the "flowers" of the coral, and who 

 wrote the Histoire physique de la mer; and the specific form, as 

 well as the colour and other attributes of the egg have been 

 again and again discussed, and not least by the many dilettanti 

 naturahsts of the eighteenth century who soon followed in 

 Marsigli's footsteps f. 



* De avibus circa aquas Danuhii vagantibus et de ■ipsarum Nidis (Vol. v of 

 the Danuhius Pannonico-mysicus), Hagae Com., 1726. 



^ Sir Thomas Browne had a collection of eggs at Norwich, according to Evelyn, 

 in 1671. 



