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XL] As pointed out by Grassi, its exact position here is the interior of the labium (Fig. 107, a). Apparently the filariæ seek to emerge (for such must be their object in entering the proboscis) in pairs; at all events, in those sections which I have examined, two worms were in each instance found together, their heads abreast of each other and close to the termination of the labium in the labella. As many



as eight have been found packed together in this situation.

The parasites remain in this position awaiting an opportunity to enter a warm-blooded vertebrate host when the mosquito next feeds on such. This they appear to do by penetrating the thin membrane that unites the labella to the tip of the proboscis, and so passing on to the surface of the skin, which they penetrate in the neighbourhood of the puncture made