The specific characters of the Eimeria, with special reference to the coccidia of the fowl.

The differentiation of species of Eimeria is discussed with special reference to those occurring in the domestic fowl. Details of the morphology of the oocysts and other developmental stages of the parasites, their location in the host and the characteristics of the lesions produced, the timing of the patent and prepatent periods, host- and site-specificity and immunological specificity may be used as aids for specific identification. A single criterion is usually insufficient for differentiation and depending upon the species, different characters vary in significance. Quantitative cross-immunity tests appear to be the most satisfactory means available for the differentiation of species of Eimeria affecting chickens.