Of 54 sparrows examined in or near Princeton, coccidia were found in 43, or 80 per cent. Most of the negative cases were encountered in November and December. In the summer and fall practically all were infected. These figures agree closely with Hadley's, who found 79 per cent infected from May to December.
Cultures of feces on agar showed that, at least in this locality, the infecting species belongs to the genus Isospora or Diflospora and not to Eirneria.
In a recent paper by Hadley, which came into our hands after the manuscript had gone to press, the author now refers blackhead to invasions of Trichomonas. It is not possible to consider here the evidence on which this conclusion is based.