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698 definitive host by mosquito bite. Whether it may obtain an entrance by any other channel or medium it would be hard to prove and rash to deny. That the young filariæ can live in water for a time (about seven hours) is certain; it is conceivable that some of them, such as those which at the completion of their stage of development in the mosquito find their way into the abdomen of the insect, may escape into water when the mosquito lays her eggs or dies.*

Technique.— Mr. Max Colquhoun made for me beautiful sections illustrating the metamorphosis of the filaria in mosquito by the following technique. The insects, preserved in glycerin, were soaked in dilute acetic acid 5 per cent, for one day only; then in formalin 50 per cent., water 50 per cent.,for one day; next in absolute alcohol for one day; absolute alcohol and ether, equal parts, one day; finally, in celloidin for one day. They were then sectioned, placed in strong hæmatoxylin for two hours, decolorized in acid, hydrochloric 1 per cent, and alcohol, washed in water, passed through aniline oil, xylol, and mounted in xylol balsam. Paraflin sections are not a success.

In working with fresh mosquitoes, all that is necessary is to tease up the thorax of the insect with needles in normal salt solution, and, after removing the coarse fragments of the integuments of the mosquito, apply a cover-glass and place under an inch objective. The filariæ are readily detected. If the slide is dried, fixed, and stained with a watery solution of some aniline dye or with logwood, and mounted in xylol balsam, beautiful permanent preparations will be obtained.