Heredity and sex . lant nor can the combination/ H. This scheme is only intended as a shorthand wayof indicating the results, and not as an interpretationof actual conditions. PARTHENOGENESIS A third important condition in which the heredityof sex is involved is found in parthenogenesis. It has long been known to biologists, that in manydifferent species of animals and plants eggs developwithout being fertilized. This is recognized as aregular method of propagation in some species. The 174 HEREDITY AND SEX eggs are produced in the same way as are other are produced in ovaries that ha
Heredity and sex . lant nor can the combination/ H. This scheme is only intended as a shorthand wayof indicating the results, and not as an interpretationof actual conditions. PARTHENOGENESIS A third important condition in which the heredityof sex is involved is found in parthenogenesis. It has long been known to biologists, that in manydifferent species of animals and plants eggs developwithout being fertilized. This is recognized as aregular method of propagation in some species. The 174 HEREDITY AND SEX eggs are produced in the same way as are other are produced in ovaries that have the samestructure as the ovaries that give rise to ordinaryeggs. Parthenogenetic eggs differ from spores, notonly in their origin in an ovary, but in that they alsoproduce polar bodies like ordinary eggs. Most, butnot all, parthenogenetic eggs give rise, however, toonly one polar body. Some of them at least fail topass through the stage of synapsis, and, in consequence,they retain the full number of ms^i^4 Fig. 89. — Miastor, sexual male and female (to right). Three larvaewith young inside (to left). A few examples will bring the main facts before us. A fly, miastor, appears in the spring of the yearunder two forms, male and female (Fig. 89). The eggsare fertilized and each produces a worm-like larva produces eggs while still in the larval eggs develop without fertilization, and producenew larvae, which repeat the process. This methodof propagation goes on throughout the rest of theyear until finally the adult winged flies reappear. The bee is the most remarkable instance, for here PARTHENOGENESIS 175 the same egg will produce, if it is fertilized, a female(queen or worker), or, if it is not fertilized, a male(drone). If the queen deposits an egg in a cell of thecomb that has been built for a queen or a worker, shefertilizes the egg; if in a drone cell, the egg is not fertil-ized. We need not conclude that the queen knowswhat she is about
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectsex, bookyear1913
