. The microscope and its revelations. er than the the very delicacy of thismembrane, and its consequenteasy fracture, it is often want-ing. In Plate I, fig. 4, we presentobject magnified 2,000 diameters. In Isthmia nen-osa, a side and front view of which are seen infig. 457, a similar construction is discoverable. In this diatom thecoarse areolations are very large and the silex correspondingly thick ;but the inner membrane is excessively thin and delicate. The per-forations are large and irregular in shape around the margin, butsmall and circular in the centre. In fig. 443 the form
. The microscope and its revelations. er than the the very delicacy of thismembrane, and its consequenteasy fracture, it is often want-ing. In Plate I, fig. 4, we presentobject magnified 2,000 diameters. In Isthmia nen-osa, a side and front view of which are seen infig. 457, a similar construction is discoverable. In this diatom thecoarse areolations are very large and the silex correspondingly thick ;but the inner membrane is excessively thin and delicate. The per-forations are large and irregular in shape around the margin, butsmall and circular in the centre. In fig. 443 the form of areola-tions is shown, and a broken membrane seen, with the fracturepassing through the Not less interesting is the beautiful form Aulacodiscus Klttonii;a photo-micrograph of this magnified 270 diameters is seen in PlateI. fig. 5; while a small portion of the centre of a kindred form, 1 Note on the finer structure of certain diatoms, E. M. Nelson and G. <_. Karop,Joitrn. Qxekett Club, vol. ii. ser. ii. p. Fi«. 441. -Magnification of ultimate struc-ture of Cuscinodisciin asteromphalus,from a drawing by Messrs. Nelson andKarop (Juiirn. Qitekftt Club, vol. ii. p. 2(59). photo-micrograph of the same 592 MICROSCOPIC FORMS OF VEGETABLE LIFE — THALLOPHYTES . I. Stm-tii, magnified times, is shown in fig. (5 in the sameplate. The beaded appearance of diatom-valves is so universal in allthose which have been examined, that it must be regarded ascommon to all diatoms, although this is not yet absolutely , while it is admitted that the beading of the valves may becommon to all diatoms, it cannot be regarded as proved that thesiliceous envelope is composed of globular particles of silex arranged
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
