228 SUPPLEMENT TO 



which, though adult, have not attained the maximum 

 size, are represented, this descending cavity, though 

 overlooked by me, should have been shown, for it 

 must certainly have existed. 



Its presence was first observed by the Honourable 

 L. G. Dillon, who detected it when tracing the course 

 of the main tube upwards from below. I had always 

 followed the tube from above downwards, and in so 

 doing must have unwittingly filled up the descending 

 cavity (the existence of which I was far from sus- 

 pecting) with detached particles of earth. 



I will own that, when Mr, Dillon first showed me 

 this new feature, I hoped that it might prove to be 

 something accidental and exceptional ; and it was 

 only after careful examination of a large series of 

 nests of all sizes, that I gradually and almost un- 

 willingly admitted that this descending cavity formed 

 an important feature in the typical structure of the 

 nests. 



I now see, however, that the presence of this cavity 

 adds considerably to the interest of the structure as a 

 whole, and places its architect quite at the head of 

 all the builders of trap-door nests. This type should 

 now be called, for the sake of distinction, the double- 

 door, hranched, cavity, wafer nest, to avoid confusion 

 with the Hyeres hranched nest. 



I am now about to endeavour to atone for my past 

 oversight by giving new illustrations (Plate XIX., 

 figs. A and B) and descriptions of this very remarkable 

 nest ; while I would at the same time beg the indul- 

 gence of my readers for past and present shortcomings, 

 reminding them that the interest which attaches to 

 structures of this kind is proportioned to the com- 



