SECTIONAL TRANSACTIONS.— D. 363 



time, or keen amateur, curator fulfils its function unless it can form part of 

 a series of similar institutions supplied with circulating collections from 

 some central organisation. 



Mr. J. A. S. Stendall. 



Mr. A. W. Boyd.— The British Trust for Ornithology ; Swallow Enquiry 

 (11.30). 



Mr. D. Lack. — The bird census as an ecological method (12.0). 



With the investigation of the ecological principles underlying bird distri- 

 bution, the vague terms, common, rare, etc., must be replaced by definite 

 numbers. Census work is arduous, and only a limited number of types of 

 bird and environment are suitable for large-scale investigations. For several 

 conspicuous species, breeding censuses have been taken over wide areas, and 

 in various areas the total breeding population of all species has been counted. 

 Some of these censuses have been repeated over a series of years. Winter 

 populations, which are more fluctuating, have been estimated in a few 



cases. 



Census work is providing information on the degree of annual fluctuations 

 in breeding populations, on the relation between breeding and non-breeding 

 individuals, on the size of clutch and nesting mortality, on the changes in 

 bird population with a changing habitat, on the size and degree of uniformity 

 of defended breeding territories, and other problems. Progress is being 

 made, but the study of the factors influencing bird distribution is still in its 

 infancy. 



Dr. W. K. Spencer, F.R.S. — Function and adaptation in early Echino- 

 dermata (12.30). 

 The Cambrian and Ordovician rocks contain some beds composed of 

 very fine mud and containing a fauna which represents old sea bottoms. 

 The fine sediment has preserved extremely good detail of the original 

 animals, and reconstruction can be made not only of the form but of habit. 

 Short accounts will be given (a) of Stromatocystis, one of the oldest known 

 fossils which lived in intertidal waters — this form is not ancestral to the 

 Eleutherozoa, as suggested by various writers, but a highly specialised ciliary 

 feeder : comparisons can be made which suggest that Stromatocystis and 

 other Edrioasteroids are related to the Blastoidea ; (b) of some Cystoids in 

 which the plates of the theca had important functions in respiration, there 

 being a circulatory system within the plates themselves ; (c) of Cothurno- 

 cystis, which turned itself over on its side, like the flatfish of to-day. 



Afternoon. 



Joint Discussion with Section M (Agriculture) on The poultry industry 

 (Section D room) (2.15). 



Mr. W. Hamnett. — The poultry industry and its problems. 



The main problems affecting the poultry industry are concerned with 

 (1) breeding, (2) nutrition, (3) disease. It should be realised that the 

 workers on the nutritional and disease side are not expected to work miracles 

 on birds that have been bred without regard to constitutional vigour. Low 



