. The physical basis of heredity . Heredity. a SdyAiiJi';iy^4'»'r,*vV«{VlMr^ji,V&-^S«A?J:!^^^^^ Fig. 83.—Extrusion of the polar body from a male-producing egg with lagging chro- mosomes on the spindle, a; and extrusion of the polar body from a female-producing egg, b; in Phylloxera. In the phylloxerans there are two parthenogenetic generations followed by a sexual one (Fig. 82). In the sec- ond parthenogenetic generation two whole chromosomes leave certain eggs (Fig. 83) passing into the single polar body which is given off from the egg. Such eggs have two less sex-chromosomes and develop
. The physical basis of heredity . Heredity. a SdyAiiJi';iy^4'»'r,*vV«{VlMr^ji,V&-^S«A?J:!^^^^^ Fig. 83.—Extrusion of the polar body from a male-producing egg with lagging chro- mosomes on the spindle, a; and extrusion of the polar body from a female-producing egg, b; in Phylloxera. In the phylloxerans there are two parthenogenetic generations followed by a sexual one (Fig. 82). In the sec- ond parthenogenetic generation two whole chromosomes leave certain eggs (Fig. 83) passing into the single polar body which is given off from the egg. Such eggs have two less sex-chromosomes and develop parthenogenetically into males. In other eggs of the same generation all four sex-chromosomes are retained after the polar body is produced. These eggs also develop parthenogenetically, but produce females. Similar changes take place no doubt in the aphids, for the males have been shown to have one less chromosome than the female, although the loss of one. 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 Morgan, Thomas Hunt, 1866-1945. Philadelphia : Lippincott
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherphiladelphialippin
