. I protozoi. I protozoi. 202 i protozoi di ciglia, che qui si fondono per formare la caratteristica membranelles ; la bocca, come in Heterotrichida, restante sul lato ventrale. In più forme generalizzate, come Peritromns o Oxytricha (£), le ciglia sono ben distribuiti sulla superficie ventrale, ma nella maggior parte degli altri H ypotrichida sono ridotti, e molti sono obliterati o fuso in carattere- istic cirri. I cirri nel Oxytrichinae sono in modo primitivo ar- variava in sei righe, ma in vari generi il numero diventa ridotta, e spesso solo iso- affini cirri mark orig

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. The Protozoa. Protozoa. 202 THE PROTOZOA of cilia, which are here fused to form the characteristic membranelles ; the mouth, as in Heterotrichida, remaining on the ventral side. In the most generalized forms, such as Peritromns or Oxytricha (£), the cilia are well distributed over the ventral surface, but in most of the other H ypotrichida they are reduced, and many are obliterated or fused into character- istic cirri. The cirri in the Oxytrichinae are primitively ar- ranged in six rows, but in the various genera the number becomes reduced, and frequently only iso- lated cirri mark the original position of the row (C). The Peritrichida, finally, show the most far-reaching devia- tions from the holo- trichous type, from which they are prob- ably derived through the Heterotrichida and the Hypotrichida. In all members of this group the adoral zone is continued into a spiral, which may have as many as five. D Fig. 114.â Illustrating Bfltschli's view of the origin of the Vor ticellidae. [BUTSCHU.] The Trichodina form C is supposed to have arisen from the Complete turns {Ccim- Lichiwpkora-ike form A by the outgrowth of the lower ciliated panclla). The chief area, first forming an intermediate stage B. This ring of cilia ;nrprp<;t- r^rovnino- becomes lost in the V01 ticellidae, appearing only when the indi- lu^clcbL â LUIlLCIlutig viduals are free-swimming. D, E. Side and front of Lichnophora this adoral zone is ap- that in some forms the spiral is turned to the left, similar to that of all of the other .groups of Ciliata, . while in other forms, belonging to the great family of the Vorticel- lidas, the spiral is turned to the right. The sinistral type of the Peritrichida originates, according to Butschli, from an hypotrichous form, becoming attached at the posterior half of the ventral surface, .. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustra

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• bookauthorcalkinsg
• bookcentury1900
• bookdecade1900
• bookyear1901