Papio cynocephalus from French Guinea frequently harbours Loa papionis n.sp. The intermediate host is unknown. The larvae, in contradistinction to those of the human parasite Loa loa, show no diurnal periodicity.

The occurrence of bacterial disease in adult L. papionis would seem to be a novelty; at any rate I could find no mention of diseased filariae in the literature.

In so far as the biology of Microloa loa is concerned, I am inclined to doubt the correctness of the opinions expressed by Rodenwalt and Fülleborn concerning the structures they term “executory and genital cells”: the current hypotheses concerning the significance of these structures and of the “central viscus,” clearly need revision. Manson's “buccal apparatus” would seem to be nothing more than an optical illusion, while the “neck” or “shoulder” described by the older observers as existing in adult L. loa after fixation, was evidently due to imperfect technique.

I have drawn attention to the desirability of standardising the technicalities which are such essential preliminaries to the accurate mensuration of micro-filariae, and have suggested a method which has certain advantages over those at present in use.

Concerning the pathology of Loa infection, evidence both of the traumatic and toxic action of L. papionis on baboons, was obtained; moreover these parasites seemed definitely toxic for guineapigs, although the single experiment performed needs confirmation. The available evidence favours the supposition that adult baboons from an infected area possess a high degree of immunity both against L. papionis toxaemia and against reinfection by these parasites; but whether their serum is of therapeutic value for human beings infected with L. loa, requires further investigation.