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i] out a little the posterior end of the abdomen, and nick it on each side about the junction of the penultimate segment; a weak place in the exoskeleton is thus formed. The thorax being now fixed with one mounted needle, another needle placed flat on the last segment of the abdomen steadily drags this away from the rest of the mosquito. The stomach or midgut and Malpighian tubes can thus be gradually pulled out from the exoskeleton; when sufficient length of œsophagus comes into view it can be divided by a touch of the needle. The ovaries of the female and testes of the male are also pulled out with the stomach. Sometimes the stomach is found to be full of blood or other food; in this case it is necessary to make a nick in the stomach: the weight of the cover-glass, which should now be applied, by its gentle pressure may express the blood. Occasionally it is necessary to wash the blood away, by allowing the stomach to refill with saline solution and then pressing on the cover-glass, and repeating the process as often as may be requisite.

The salivary glands, lying in the prothorax, can sometimes be obtained by pulling them out in dragging off the head. This method should be avoided if possible, as the glands are difficult to separate from the head, and it is impossible to compress the head without crushing the eyes; the pigment thus set free interferes with a microscopical examination. The simplest and most certain method of procuring the salivary glands is, after cutting off the head, to divide the thorax obliquely, so that its anterior portion, including the attachments of the anterior and middle pair of legs, is separated from the rest of the trunk. This portion contains both salivary glands. The exoskeleton should then be broken up with needles into five or six pieces in normal salt solution. A cover-glass is applied and steady pressure exercised with the point of the needle over each fragment of the exoskeleton. In this manner the glands are separated from the chitinous fragments, and can be readily examined. In the majority of dissections at least five out of the six lobes will be exposed undamaged.

In the stomach wall: encysted or zygote stage (Fig. 12).—This newly acquired power of locomotion and penetration on the part of the fecundated parasite, together with other well-ascertained facts, justifies the presumption that soon after its formation the travelling vermicule, now known as an oökinete, penetrates the wall of the mosquito's stomach. Working its way through the layer of cells and the delicate basement membrane which together constitute the inner coat of this organ, it finally lodges itself among the longitudinal and transverse muscular fibres lying between this inner membrane