 | Charles Lyell - 1833 - 366 pages
...deviation can be obtained by continuing to alter the circumstances, though ever so gradually,—indefinite divergence, either in the way of improvement or deterioration,...and not to the intermixture of hybrid with hybrid. Gthly. From the above considerations, it appears that species have a real existence in nature, and... | |
 | sir Charles Lyell (bart.) - 1835 - 500 pages
...constant laws, and the capability of so varying forms part of the permanent specific character. 3dly. Some acquired peculiarities of form, structure, and...and not to the intermixture of hybrid with hybrid. Gthly. From the above considerations, it appears that species have a real existence in nature; and... | |
 | Benjamin Godwin - 1835 - 384 pages
...kind of change can produce, may usually be effected in a brief period of time, after which no further deviation can be obtained by continuing to alter the...mules with individuals of pure species, and not to the intermixure of hybrid with hybrid. " Gthly. From the above considerations, it appears that species... | |
 | 1850 - 608 pages
...least excess beyond the defined limits being fatal to the existence of the individual. 1 ."•!•!. The intermixture of distinct species is guarded against...relate to the crossing of mules with individuals of the pure species, and not to the intermixture of hybrid with hybrid. ' 6th. From these considerations... | |
 | 1850 - 600 pages
...and the least excess beyond the defined limits being fatal to the existence of the individual. " 5th. The intermixture of distinct species is guarded against...relate to the crossing of mules with individuals of the pure species, and not to the intermixture of hybrid with hybrid. " 6th. From these considerations... | |
 | John Holmes Agnew, Walter Hilliard Bidwell - 1850 - 604 pages
...and the least excess beyond the defined limits being fatal to the existence of the individual. " 5th. The intermixture of distinct species is guarded against...sterility of the mule offspring. It does not appear tiiat true hybrid races have ever been perpetmted for several generations, even by the assistance of... | |
 | Thomas Ragg - 1858 - 456 pages
...can produce, may usually be effected in a brief period of time, after which no deviation can be made by continuing to alter the circumstances, though ever...of man ; for the cases usually cited relate to the crossings of mules with individuals of pure species, and not to the intermixture of hybrid with hybrid.... | |
 | Maine. Board of Agriculture - 1859 - 552 pages
...regard to the reality of species in nature ;" the following being a part of the fifth : (Ibid p. 589.) " It does not appear that true hybrid races have ever...and not to the intermixture of hybrid with hybrid." Again Dr. Browne argues against crossing together different varieties of the same species, and in this... | |
 | John Phillips - 1860 - 280 pages
...beyond the definite limits being fatal to the existence of the individual. '5. The intermixture of the distinct species is guarded against by the aversion...and not to the intermixture of hybrid with hybrid. '6. From the above considerations, it appears that species have a real existence in nature; and that... | |
| |
The intermixture of distinct species is guarded against by the aversion of the individuals composing them to sexual union, or by the sterility of the mule offspring. It does not appear that true hybrid races have ever been perpetuated for several generations,... 
