VI. INTRODUCTION. 



disadvantages. To gum* over the hole through which the egg 

 was blown, a round piece of thin white paper, larger or 

 smaller according to the size of the egg ; and on that ticket 

 to write the number of the species in this Catalogue, with its 

 distinguishing letter a, h, or c. This ticket, (which may be 

 tinted to match the colour of the q^^) thus fixed over the hole, 

 presents the two-fold advantage of adding to the sohdity of 

 the egg, by keeping the edges of the hole from chipping; 

 while, in the event of a mistake in the number inscribed upon 

 it, the ticket may easily be removed with a little warm water, 

 without risk of injury to the egg. And, when by accident 

 an egg thus ticketted has been mixed with other species of 

 similar shape or colom-, (as may frequently happen in several 

 of the genera), a simple reference to its number in the 

 Catalogue will at once enable the collector to restore it to 

 its proper place in the collection. 



In the present advanced state of Oology, few collectors wish 

 to limit themselves to only one specimen of each species ; but 

 all those who collect for a scientific pm-pose, endeavour to 

 obtain, not only all the eggs of one nesf, but also varieties of the 

 species ; which in the case of the commoner buds, sometimes 

 amount to a great many. Most of those duplicates are kept 

 separately, the systematic collection embracing besides the 

 eggs of one nest, or the number laid by each bird, only one 

 or two of the most striking varieties. 



This Catalogue is intended to apply only to such a 



* Gum arable dissolved in water is preferable for this purpose to either 

 glue or paste ; from its not being liable to be attacked by insects. 



