THEIR REPRODUCTION (EGGS) 279 



exclusion. As pointed out by Professor Newton, 

 these markings are generally and normally de- 

 posited in a circular form — as spots of varying 

 size — but in the passage of the ^gg through the 

 oviduct many of them become blurred, pro- 

 tracted, and smeared in endless series of com- 

 binations, and then the egg is blotched, or 

 receives that appearance with which every egg 

 collector is so familiar. Many of these blotches 

 or patches of colour are protracted in some par- 

 ticular direction, as the egg apparently passes on 

 with a rotatory motion towards the vent. This 

 explains the marked spiral deposition of the 

 markings on many eggs. But the eggs of all 

 birds, with the sole exception of those of the 

 Game Birds, as we discovered long ago when 

 working with the late Henry Seebohm, have two 

 very distinct types of markings. If we examine 

 an egg of a Guillemot, for instance, we shall 

 find that amongst the richer spots and blotches 

 there are others (varying in amount to a great 

 extent on individual eggs) much paler in colour, 

 due to a thin coating of shell material lying over 

 them. These paler markings must be deposited 

 at the earlier stage of the colouring process, and 

 may be either circular or protracted into blotches 

 and irregular stains. This may be proved by 



