Royal Australasian Ornithologists Union early 20th century called themselves 'oologists', though the distinction between the notionally scientific discipline of oology and simple egg-collecting was blurred. Identification of any but the most common and distinctive species usually entailed the collection of specimens to be made into study skins. Modern field-guides did not exist and few people could afford the massive multi-volume, lavishly illustrated, handbooks of John Gould and Gregory Mathews. However, both Archibald J. Campbell and Alfred North had produced comprehensive guides to what was known about the nests and eggs of Australian birds, with illustrations of the eggs rather than of the birds themselves,
The Philadelphia study development to display any social significance. The nearly completed and most advanced changes displayed the most stability within the study and showed intermediate correlation with the middle classes. The new and vigorous changes—the focal point of the study—displayed the strongest curvilinearity and most clearly encompassed the linguistically innovative nature of the inner classes. Through these Results, Labov asserted the truth and significance of what he named the Curvilinear Principle. With the social information gathered from the interviews, he discovered that it is not the education or occupation factors that drove the middle class to spur linguistic change. Rather, it was