| → The early death of hybrid 1866 1869 |
| With plants, hybridised 1872 |
|
| → occurs in 1866 1869 |
| often perish in a 1872 |
|
| → embryos produced from eggs 1866 |
| embryos produced from the eggs of silk-moths, 1869 |
| the embryos within the eggs of silk moths 1872 |
|
| → like those produced by the crossing of two distinct species, passed 1866 |
| passed 1869 |
| pass 1872 |
|
| → perished; this has been observed by M. Jourdan with the unimpregnated eggs of the silk-moth. 1866 |
| perished like the embryos produced by a cross between two distinct species. 1869 |
| perish like the embryos produced by a cross between distinct species. 1872 |
|
|
period. This latter alternative has not been sufficiently attended to; but I believe, from observations communicated to me by Mr. Hewitt, who has had great experience in hybridising pheasants and fowls, that the early death of the embryo is a very frequent cause of sterility in first crosses. Mr. Salter has recently given the results of an examination of about 500 eggs produced from various crosses between three species of Gallus and their hybrids; the majority of these eggs had been fertilised; and in the majority of the fertilised eggs, the embryos
been
partially developed and had then
or had become nearly mature, but the young chickens had been unable to break through the shell. Of the chickens which were born, more than four-fifths died within the first few days, or at latest weeks, "without any obvious cause, apparently from mere inability to live;" so that from the 500 eggs only twelve chickens were reared.
→The early death of hybrid
embryos probably
→occurs in
like
at least it is known that hybrids raised from very distinct species are sometimes weak and dwarfed, and perish at an early age; of which fact Max Wichura has recently given some striking cases with hybrid willows. It may be here worth noticing that in some cases of parthenogenesis,
→embryos produced from eggs
which had not been fertilised,
→like those produced by the crossing of two distinct species, passed
through their early stages of development and then
→perished; this has been observed by M. Jourdan with the unimpregnated eggs of the silk-moth. Until becoming acquainted with these facts, I was unwilling to believe in the frequent early death of hybrid embryos; for hybrids, when once born, are generally healthy and long-lived, as we see in the case of the common mule. Hybrids, however, are differently circumstanced before and after
when born and
|
