The disease known as Turning Sickness was first recorded by Mettam (1934) in this journal and later more fully described by Mettam & Carmichael (1936).

The condition has been defined as a protozoan encephalitis of cattle and one of the most striking features of the disease is the demonstration of schizonts indistinguishable from those of East Coast fever in the cerebral lesions of affected animals.

1. A detailed morphological study has been made of the amoeba, parasitic in larvae of Trichocera, which was described by Keilin (1917) under the name Entamoeba mesnili.

2. This study shows that the parasite cannot be included in any of the existing genera of parasitic amoebae and the new genus Dobellina is formed for it. A diagnosis of the genus Dobellina is given.

3. In Cambridge Trichocera larvae were never found infected with Dobellina mesnili earlier in the winter than January and the infection rate appears to be highest (up to 92%) towards the end of January and in February. Infected larvae were never found later in the year than May.