The microscope and its revelations . the spotted lens orby the paraboloid (§ 61), is much to be preferred for thispurpose, to the ordinary mode of illuminating opaque objectsby incident light from a condenser, although this may beadvantageously had-recourse-to, by the Microscopist who isunprovided \\dth these appurtenances. No class of objects ismore suitable than these to the Binocular Microscope(§ 40); the stereoscopic projection of which causes them tobe presented to the minds eye in complete relief, so as tobring-out with the most marvellous and beautiful effect alltheir delicate sculpture
The microscope and its revelations . the spotted lens orby the paraboloid (§ 61), is much to be preferred for thispurpose, to the ordinary mode of illuminating opaque objectsby incident light from a condenser, although this may beadvantageously had-recourse-to, by the Microscopist who isunprovided \\dth these appurtenances. No class of objects ismore suitable than these to the Binocular Microscope(§ 40); the stereoscopic projection of which causes them tobe presented to the minds eye in complete relief, so as tobring-out with the most marvellous and beautiful effect alltheir delicate sculpture, reminding the observer (to comparesmall things with great) of the finest specimens of the hollowivory balls carved by the Chinese.* 295. Sponges.—xUthough this tribe has been bandied fromthe Animal to the Yegetaljle kingdom, and back again, severaltimes in succession, yet its claim to a place among theProtozoa may now be considered as pretty certainly deter-mined, by the information derived from Microscopic examina- FiG. -f-^^ ^^^17^-ZS-^^^^ structure of Grantia compressa:—A, portion molerately mag-nified, showing general arrangement of triracliate spicules andintervening tissue;—b, small portion highly magnified, showingciliated ceUs. tion of its minute structure. Eor in the living Sponge, theskeleton, usually composed of a fibrous network strengthenedby spicules of mineral matter, is clothed with a soft flesh; * For a fuller description of this group, see Prof. Ehrenbergs Memou-s inthe Transactions of the Berlin Academy for 1846,^^1847, and his recently-pubhshed Mierogeologie; also Ann. of Xat. Hist., 1847. 524 rORAMINIFEKA, POLYCYSTIC A, AND SPONGES. and this iiesli has been found by Dujardin and all subsequentobservers to consist of an aggregation of Amoeba-like bodies(Fig. 217, b), some of which (as Mr. Dobie has shown*) arefurnished with one or more long cilia, closely resembling thoseof Volvox (Fig. 70, i), by the agency of which, a current ofwater is kep
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