Heredity and sex . n paramoecium tomean that a recombination of the hereditary factorstakes place. Some of these combinations may be morefavorable for a given environment than are these will produce more offspring, they will soonbecome the predominant race. The next diagram (Fig. 100) will serve to recall theprincipal facts in regard to conjugation in paramoe-cium. Two individuals are represented by black andwhite circles. At the time of conjugation the smallor micronucleus in each divides (B), each then dividesagain (C). Four nuclei are produced. One of thesemicronuclei, the one
Heredity and sex . n paramoecium tomean that a recombination of the hereditary factorstakes place. Some of these combinations may be morefavorable for a given environment than are these will produce more offspring, they will soonbecome the predominant race. The next diagram (Fig. 100) will serve to recall theprincipal facts in regard to conjugation in paramoe-cium. Two individuals are represented by black andwhite circles. At the time of conjugation the smallor micronucleus in each divides (B), each then dividesagain (C). Four nuclei are produced. One of thesemicronuclei, the one that lies nearest the fusion point,divides once more, and one of the halves passes into theother individual and fuses there with another process is mutual. Separation of the two indi-viduals then takes place and two ex-conjugants areformed. Each has a new double nucleus. This nu- 208 HEREDITY AND SEX cleus divides (G) and each daughter nucleus dividesagain (H), so that each ex-conjugant has four Fig. 100. — Diagram to show the history of the micronuclei of twoParamoecia during (A~F) and after (F-J) conjugation. Compare this dia-gram with Fig. 2. Another division gives eight nuclei in each. The para-mcecium itself next divides—each half gets four second division takes place, and each gets two ofthe nuclei. Four new individuals result. In each of FERTILITY 209 these individuals one of the nuclei remains small andbecomes the new micronucleus, the other enlarges toform the new macronucleus. Thus from each ex-con jugant four new paramoecia are produced, whichnow proceed to divide in the ordinary way, themicronucleus and the macronucleus elongate and divideat each division of the animal. It is customary to regard some phase in this processas involving a reduction division in the sense that aseparation of the paired factors takes place. If thisoccurs prior to interchange of micronuclei {E), then eachex-conjugant corresponds to an egg after fertil
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectsex, bookyear1913
