82 Exhibits in Natural History. [Sess. 



measurement the distance between the stage micrometer and 

 the eyepiece one should be ten inches. 



It is hoped that the above notes on a particularly dry 

 subject "will be found intelligible, as well as useful, to those 

 members of the Society who work with the microscope. 



EXHIBITS IN NATURAL HISTORY. 



There were exhibited throughout the Session, at the winter 

 evening meetings of the Society, a large number of interesting 

 objects connected with Natural History, the principal of which 

 were the following : — 



By Mrs Sprague. 



Edible Birch' -nests. — The nests exhibited were three in number, one of 

 which was white, or rather pale yellow, and very free from extraneous 

 matter ; the others were much darker, and contained many feathers, which 

 seemed to have been intentionally used by the bird in constructing the 

 nest. The nests are composed of the salivary secretion of the bird. The 

 white ones are the first that are made each year, while the secretion is 

 copious ; and the less pure specimens are constructed after the first-made 

 nests have been removed. The birds which build these nests belong to the 

 genus Collocalia, or Swiftlet, of which there are many species. Judging 

 from analogy, probably each species makes a nest with peculiarities of its 

 own. The largest of the three nests exhibited was about 2 inches wide 

 and 2h inches long ; and in each of them the successive layers by which 

 the nest was built up, could be distinctly traced. The nests are made into 

 soup, which is highly esteemed by the Chinese, and is sometimes intro- 

 duced as a curiosity at the dinners of Europeans resident in the East. 



Poppy-heads pierced by Tomtits. — Small birds, as is well known, are very 

 fond of poppy seeds, which are sold under the name of maw seed ; and the 

 tomtits, having discovered that these palatable seeds are to be found in 

 poppy-heads, make a practice every autumn of boring holes in the ripe 

 poppy-heads in the garden at Marchfield, Davidson's Mains. Mrs Sprague 

 has repeatedly seen them at work, clasping the flower-stalk just below the 

 capsule, and boring holes into the latter. 



Trap-door Spiders' Nests. — These were procured by Mrs Sprague during 

 a residence at Mentone in 1889. They are common in the olive terraces 

 there, but can only be discovered by close observation. The existence of 

 one is indicated by a very faint circle in the hard ground under the olive 

 trees ; and the lid, which is perfectly flush with the ground, can be easily 

 raised with the help of a pin or a penknife. The spider's nest, or rather 



