July 30, 1949. Both infections were light ones, thin smears of the heart blood containing from four to seven trypanosomes each.

Ericentrus rubrus (Hutton) is now given as an additional host of T. tripterygium, a 25 mm. example collected at Island Bay on March 15, 1951, being lightly infected. Four more examples of T. varium and two more of T. medium were found to be parasitized by this flagellate. All the infected fishes were collected on the sea coast to the south of Wellington, from Island Bay to Moa Point, Lyall Bay, during August, 1949, and December, 1950. The parasite rate in a 64 mm. T. medium from Moa Point (December 25, 1950) was appreciably higher than usual, a single thin smear of heart blood containing 59 trypanosomes (av. 3 per 10,000 erythrocytes).

This trypanosome having only recently been described and figured, its morphology will not be fully detailed here. It shows marked polymorphism, small slender forms, intermediate forms and stout, degenerating forms occurring. The average dimensions of the intermediate form, which is the commonest one, are given below, as published in the original description.

The extremes of the various dimensions for all forms of T. tripterygium are:—

Small slender forms of T. tripterygium have an oval nucleus situated some 28 per cent. of the total body length from the anterior extremity and occupying the entire width of the body. As the flagellate increases in size its nucleus becomes rounded, distinctly karyosomatic and more posteriorly situated. In the common intermediate form the nucleus is from 40–50 per cent. of the total body length from the anterior extremity. Although the actual distance between the kinetoplast and the posterior extremity of the body is approximately the same as in the smaller forms, this distance expressed as a percentage of the total body length is considerably reduced (from 17–24 per cent. to 9 per cent.). Similarly, the actual length of the free flagellum is substantially unchanged although it is relatively much shorter in proportion to the length of the body. Stout, degenerating trypanosomes may attain 7.4μ in breadth. These have a very short free flagellum, in consequence of a marked anterior extension of the cytoplasm along this organelle. This extension also results in the nucleus becoming centrally, or even somewhat posteriorly, situated. Myonemes are conspicuous in the species, five or six being clearly evident in the cytoplasm of the intermediate form.