1.Exoerythrocytic schizogony has been looked for in 18 cases of infection with Plasmodium relictum var. matutinum, and demonstrated in 9. It has been found both in blood-induced infections and those resulting from the bites of infected mosquitoes.
2.Exoerythrocytic schizonts in this subspecies present no particular characteristics not seen in other species, except that they often appear vacuolated in stained preparations. Similar vacuoles have been rather frequently seen in the larger erythrocytic forms (particularly schizonts) also, and this is believed to be further evidence that both these types of schizogony are part of the life-cycle of the same parasite.
3.Most of the cases in which exoerythrocytic forms have so far been observed have shown a preponderance of such stages in the brain. The erythrocytic schizonts also appear to show a tendency to localise in the internal organs, especially in the liver.
4.Transmission of this subspecies has been effected by Culex pipiens.
5.Although Plasmodium relictum var. matutinum is in most respects indistinguishable on morphological grounds from other strains of Plasmodium relictum, it presents a clearcut difference with respect to the number of merozoites produced per segmenter. The mean is about sixteen. Physiologically, as already pointed out by others, it is very different.
Aided by a grant-in-aid from the American Philosophical Society and Sigma Xi. The author also wishes to express his gratitude to Miss Ellen Counts for assistance.