The differentiation of the eggs of Haemonchus contortus and Ostertagia species of the sheep and a note on the relative generic egg-laying rates

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Abstract
1. In a mixed infection in which Haemonchus contortus, Ostertagia circumcincta and O. trifurcata predominated, the lengths were plotted against widths of eggs obtained from faeces.2. Two-dimensional groups approximating to normal frequency distributions, showing little overlap, were observed.3. The statistical ranges of means plus and minus twice the standard deviation for the two groups barely touched. These were, to the nearest micron, 68–84 by 41–51 for Haemonchus contortus and, for the Ostertagia group, 83–103 by 46–52.