. The microscope and its revelations. that previouslydescribed that there would atfirst seem ample ground forseparating the simple and thecomplex types as distinct the test furnished by theexamination of a large numberof specimens, which ought never to be passed by when it can possiblybe appealed to, furnishes these very singular results: 1st. that thetwo forms must be considered as specifically identical ; since there isnot only a gradational passage from one to the other, but they areoften combined in the same individual, the inner and first-formedportion of a large disc frequent
. The microscope and its revelations. that previouslydescribed that there would atfirst seem ample ground forseparating the simple and thecomplex types as distinct the test furnished by theexamination of a large numberof specimens, which ought never to be passed by when it can possiblybe appealed to, furnishes these very singular results: 1st. that thetwo forms must be considered as specifically identical ; since there isnot only a gradational passage from one to the other, but they areoften combined in the same individual, the inner and first-formedportion of a large disc frequently presenting the simple type, whilstthe outer and later-formed part has developed itself upon the complex ;2nd, that although the last-mentioned circumstance would naturallysuggest that the change from the one plan to another may be simplya feature of advancing age, yet this cannot be the case: since,although the complex sometimes evolves itself even from the veryfirst (the nucleus, though resembling that of the simple form, sending. FIG. G12.—Portion of animal of complextype of Orbitolites complanata:a a, b b, the upper and lower rings oftwo concentric zones; c c, the upperlayer of superficial sub-segments, and<l <J, the lower layer, connected with theannular bands of both zones; e e ande e, vertical sub-segments of the twozones. 810 MICROSCOPIC FORMS OF ANIMAL LIFE out two or more tiers of radiating threads), more frequently thesimple prevails for an indefinite number of zones, and then changesitself in the course of a few zones into the complex. No depart-ment of natural history could furnish more striking instances thanare afforded by the different forms presented by the foraminiferaltypes now described, of the wide range of variation that may occurwithin the limits of one and the same species; and the microscopistneeds to be specially put on his guard as to this point in respect tothe lower types of animal as to those of vegetable life, since thedetermination of f
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
