Micropus (mikropus)

[NL., 2. In ichth., a name of two genera of fishes, one founded by J. E. Gray, 1831, the other by Kner, 1868.-3. In entom., a tropical American genus of lygæid bugs erected by Spinola in 1837. For a long time the destructive chinch-bug of the United States was called M. destructor, but it is now placed in the genus Bli us. micropylar (mikro-pi-lär), a. [ 3752 parts so that its length (and thus the distance between the gla es) can be varied at will; it is then called a draw - tube. The object under examination is placed upon a support, called the stage, beneath the objective; position this may be adjusted by the hand, or, better, the object and the stage (then called a mechanical stage ) are moved together by some mechanical arrangement, as, for example, by two screws giving motions in two directions at right angles. The proper distance between the objective and the object (such that the image of the latter shall be seen en clearly, or be in focus ) is usually attained by the movement of the tube a whole. This is accomplished by the rapid motion of the coarse adjustment, and more slowly and accurately, as is nece ary in the case of high powers, by an arrangement called the slow motion or fine adjustment. The nece ary illumination is obtained by a concave mirror below the stage, which reflects the light the object. An achromatic condenser, usually in connection with dia phragm, is often added to converge the light more strongly; for opaque objects a bull's-eye condenser, a lieberkühn, or some other form of reflector is employed. The body of the microscope, with the stage, etc., is supported firmly upon a stand, and usually attached by a joint which allows of its being inclined at any desired angle between the vertical and horizontal positions. Many acce ories, or special devices applicable to particular uses, may be added to the microscope in its e ential form, as a micrometer, polarizing prisms, camera lucid a, etc. The compound microscope itself often varies widely in construction, according to the character of the work for which it is to be used. (Compare also the phrases below.) 2. [ cap.] A constellation. See Microscopium. Achromatic microscope. See achromatic. - Binocular microscope, a microscope so constructed that the object may be viewed simultaneously by both eyes, with the advan sarilyattained) that it is then seen in relief. It has a single objective, but two tubes, micropyle (mikro-pil), n. [= F. micropyle , μικρός , small, + πύλη, gate, orifice.] 1. In bot ., the orifice or canal in the coats of the ovule leading to the apex of the nucleus, through which the pollen-tube penetrates. The name is also applied to the corresponding part of the seed, which indicates the position of the embryo. See foramen , 2. See cut under amphitropous . 2. In zoöl .: (a) The scar or hilum of an ovum at the point of its attachment to the ovary. (b) Any open Any opening in the coverings of an ovum through which spermatozoa may gain acce to the interior, or a cluster of minute pores on the surface of an egg through which fertiliza- tion is effected. On the eggs of lepidopterous insects these pores often form a rosette at one end. microrhabd (mikro-rabd), n. [ μικρός , small, + NL. rhabdus , q. v.] A little rhabdus; a micro sclere or flesh-spicule of a sponge in the form of a rhabdus. W. J. Sollas, Encyc. Brit., XXII. 417. each with its own eyepiece; a prism causes the luminous rays from the objective to separate and pa through each tube. Double-bod ied microscope, a micro scope in which the object under examination can be viewed by more than one person at the same time. As in the binocular microscope, a prism divides the rays from the objective. Two other prisms receive the separated rays, and the respective pencils are directed through the different bodies of the instrument. Filar microscope, a microscope having cro -wires in the focus of the eyepiece. - Inverted or chemical microscope, one with the object-gla placed beneath the object and the stage.