. The biology of twins (mammals). Twins. Fig. 29 dition that occasionally appears in which three fetuses are alike and one quite different. A striking feature of Fernandez' collec- tion of the eggs of D. hyhridus has to do with the frequent, almost universal, occurrence of one or more degenerate embryos in an egg. These embryos may be the victims of severe competition for placental surface, or they may be the result of outgrowths produced from un- favorable regions of the ectodermic vesicle. The portion of an Qgg shown in Fig. 31 indicates that ectodermal out- growths may fail to reach the wal
. The biology of twins (mammals). Twins. Fig. 29 dition that occasionally appears in which three fetuses are alike and one quite different. A striking feature of Fernandez' collec- tion of the eggs of D. hyhridus has to do with the frequent, almost universal, occurrence of one or more degenerate embryos in an egg. These embryos may be the victims of severe competition for placental surface, or they may be the result of outgrowths produced from un- favorable regions of the ectodermic vesicle. The portion of an Qgg shown in Fig. 31 indicates that ectodermal out- growths may fail to reach the walls of the egg and, through lack of endodcrmic and mesodermic elements, may thus fail to be- come complete em-. FlG. 30 Figs. 29 and 30. Two more views of conditions like those shown in Fig. 28. There are in the upper figure 13 embryos, each with a connecting canal; .1, B, and C are evidently rudimentary or aborted embryos. In the lower figure all of the successful embryos (1-7) seem to have come from one-half of the ectodermic vesicle and only a rudimentary embryo (8) from the other half. (After Fernandez.). 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 Newman, Horatio Hackett, b. 1875. Chicago, Ill. , University of Chicago press
Size: 1630px × 1533px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookpublisherchicagoilluniversityofchicagopress, bookyear1917
