. The Protozoa. Protozoa. 182 THE PROTOZOA —pm -fto -az '-j> o c Cirri, membranelles, and membranes are each striated, and when treated with certain reagents { gold chloride, Maupas), can be reduced to separate fibres which are similar to cilia. The simplest of these aggregations are the cirri. These bundles of threads are usually pointed, and either curved or straight, forming the Grijfeln mid Haken of Ehrenberg. A simple condition is seen in the tail-like process of Urocentnim, which has a distinctly fibrillar structure and can be readily reduced to a brush of very fine hairs (Fig. 99
. The Protozoa. Protozoa. 182 THE PROTOZOA —pm -fto -az '-j> o c Cirri, membranelles, and membranes are each striated, and when treated with certain reagents { gold chloride, Maupas), can be reduced to separate fibres which are similar to cilia. The simplest of these aggregations are the cirri. These bundles of threads are usually pointed, and either curved or straight, forming the Grijfeln mid Haken of Ehrenberg. A simple condition is seen in the tail-like process of Urocentnim, which has a distinctly fibrillar structure and can be readily reduced to a brush of very fine hairs (Fig. 99). Although the striated appear- ance and the reduction to the component fibrils make it prob- able that cirri arise by the fusion of cilia, an objection is met in the fact that their de- velopment, after division, shows —em no such origin. On the con- —gO trary, they arise from the ecto- .plasm as cirri and not as cilia. This objection, however, seems hardly sufficient to counter- balance the evidence in favor of the concrescence theory, evidence which is strengthened by the position of the cirri along the lines of the cilia- markings. The membranelles are flat plates of striated appearance usually in the form of tri- angles, squares, or parallelo- grams. Each membranelle is , , inserted in a furrow below Fig. 98. — Schematic hypotnchous cihate. az, adora) zone; c, ventral cirri; em, endoral mem- which IS a basal Stripe Ot brane; eo, endoral cilia; pm, prasoral membrane ; pa, thickened protoplasm COntinU- paroral cilia; A«. praeoral cilia. oug wjth ^ longitudinal dl_ iary markings (Heterotrichida). Like the cirri, they can be readily reduced to component fila- ments resembling cilia, and there is, therefore, every reason to suppose that the membranelles which form such a characteristic differential for all orders save the Holotrichida, are merely the differ- entiated portions of the ciliary The basal stripes of the membranelles, which are spirally arranged upon
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