SECTIONAL TRANSACTIONS.— D. 365 



not ' warning ' displays. In some cases, the males gather together and 

 go through the courtship dances in bands, while in others the display is 

 performed alone, and often on a specialised dancing ground. A detailed 

 study of the plumes of the different genera brings out the remarkably close 

 relationship that exists between these structures and the mode of display : 

 in the genus Paradisea, several quite distinct types of display are found 

 and correspond very closely with the slight inter-specific differences in the 

 plumes, providing an interesting basis for the determination of the inter- 

 relationships of the species. 



Examination of the plumes, the pterylosis, the musculature, and the 

 osteology of one of the more highly specialised types indicates a strildng 

 correlation of structure, apparently subservient to the display ; and the 

 whole consideration of the sexual adornments and the manner in which they 

 are shown off opens up interesting lines of thought on the problem of 

 relationship of habit to structure. 



Friday, September 3. 



Joint Symposium with Section K (q.v.) on Recent work in genetics and 

 cytology (lo.o). 



Afternoon. 



Semi-popular lecture by Mr. L. Koch on ' How I collected bird songs ' ; 

 illustrated by gramophone records. (2.15.) 



We know that the knowledge of birds especially that of their song is not 

 very widespread. 



Some of the most beautiful lyric descriptions in our poetry and prose 

 are of the glory of bird songs. How familiar in words are the sweet flute- 

 like notes of the nightingale or the lulling and stirring songs of the woodlark. 

 Yet could anyone hope to recognise the sounds in nature merely from having 

 read these descriptions ? Curves and music notes imply just as little. 



It is only after half a century of development of that invention of Edison's 

 primitive but epoch-making phonograph that one could venture to collect 

 bird songs in the open by means of the microphone and the modern 

 moving recording studio. 



Further developments of the idea of a sound book that will add sound 

 by means of gramophone records to text and picture, is shown with British 

 bird songs. Here we have a description of the extraordinary difficulties 

 that are encountered and the endless patience required by all who are 

 concerned in watching and collecting bird songs during the night and early 

 dawn. 



A number of interesting episodes of the ' expedition ' illustrate the bird 

 song hunting. 



What bird song means and how it is uttered is mentioned and audibly 

 rendered by natural clear examples of about twenty-five of our British 

 wild bird songs. These records are not only a valuable asset to bird and 

 nature lovers, but of great importance for education and science. 



Exhibition of films of biological interest : 



Behaviour and sense physiology in butterflies, by Dr. D. Use. 



Courtship display of Birds of Paradise, illustrating Mr. C. R. Stonor's 

 paper ; shown by courtesy of Dr. J. S. Huxley. 



