. The biology of the protozoa. Protozoa; Protozoa. PHENOMENA ACCOMPANYING FERTILIZATION i05 subcylindrica, Lionotus fasciola, and in the Vorticellidae, only 1 nucleus undergoes this third division. In Onychodromus grandis, Stylonychia pustulata, and Euplotes patella, 2 nuclei; in Oxytricha fa I lax (Gregory), 2 or 3, and in Uroleptus mobilis, 2, 3 or 4 nuclei, undergo the third division. Prandtl (190(5) was the first to note a difference in size between the wandering and the stationary pronuclei (Didinium nasutum), Calkins and Cull (1907) described a similar difference in pronuclei of Parameci
. The biology of the protozoa. Protozoa; Protozoa. PHENOMENA ACCOMPANYING FERTILIZATION i05 subcylindrica, Lionotus fasciola, and in the Vorticellidae, only 1 nucleus undergoes this third division. In Onychodromus grandis, Stylonychia pustulata, and Euplotes patella, 2 nuclei; in Oxytricha fa I lax (Gregory), 2 or 3, and in Uroleptus mobilis, 2, 3 or 4 nuclei, undergo the third division. Prandtl (190(5) was the first to note a difference in size between the wandering and the stationary pronuclei (Didinium nasutum), Calkins and Cull (1907) described a similar difference in pronuclei of Paramecium caudatum and were able to trace this difference back. Fig. 154.— Uroleptus mobilis, conjugation. The interchange of pronuclei, each preceded by a characteristic "attraction ; (After Calkins.) to a heteropolar third division spindle. In other cases there seems to be no characteristic difference in size between the two pronuclei although other differences may be evident. Thus Maupas noted the presence of a dense aggregate of cytoplasmic granules at the forward pole of the advancing pronucleus of Euplotes patella and Prandtl, more pronounced astral radiations about the wandering pronucleus of Didinium nasutum. In Uroleptus mobilis such radi- ations are absent, but a fairly homogeneous condensed "sphere" of cytoplasmic substance precedes the wandering pronucleus in its migration (Fig. 154). 20. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Calkins, Gary N. (Gary Nathan), b. 1869. Philadelphia, Lea & Febiger
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