The distribution of organic cores, cones, cone junctions and pores in the egg shells of wild birds

Egg shells from 14 widely different species of wild birds were examined, using collodion casts of the inside surface of the shell. Organic cores, cones, cone junctions and pores were counted and in each case measurements of nearest neighbour distances were taken. Shell thickness was also measured. It was found that, using mean values for each egg shell, there were highly significant, and in some cases almost perfect linear relationships between core numbers, cone numbers, cone junction numbers and pore numbers on the one hand and their respective nearest neighbour distances expressed as the reciprocal of the mean of the squares of these distances on the other. The results also showed that the distribution of all four structures was not random, but had a degree of uniformity increasing up the series pores < cone junctions < cores < cones. The following relationships were also highly significant: core and cone numbers, core and cone junction numbers, and cone and cone junction numbers. The relationship of pore numbers to any of the other three structures was of no great significance. Shell thickness was related curvilinearly to core numbers and to cone numbers and linearly to nearest neighbour values for cones. It was also related to pore numbers. It is suggested that, apart from pores the other three structures and their distribution all depend upon the number of cores which are the original centres of crystallization from which the shell grows. To a lesser extent shell thickness also depends upon these structures. Tentative suggestions are also made concerning the origin of the pores.