V.] SPECIFIC STABILITY. 127 



CHAPTER V. 



AS TO SPECIFIC STABILITY. 



What is meant by the Phrase "Specific Stability;" such Stability to be expected a 

 priori, or else Considerable Changes at once. Eapidly-increasing Difficulty of in- 

 tensifying Eace Characters ; Alleged Causes of this Phenomenon ; probably an In- 

 ternal Cause cooperates. A Certain Definiteness in Variations. Mr. Darwin ad- 

 mits the Principle of Specific Stability in Certain Cases of Unequal Variability. 

 The Goose. The Peacock. The Guinea-fowL Exceptional Causes of Variation 

 under Domestication. Alleged Tendency to Reversion. Instances. Sterility of 

 Hybrids. Prepotency of Pollen of same Species, but of Different Eace. Mortality 

 in Young Gallinaceous Hybrids. A Bar to Intermixture exists somewhere. 

 Guinea-pigs. Summary and Conclusion. 



As was observed in the preceding chapters, arguments 

 may yet be advanced in favor of the opinion that species 

 are stable (at least in the intervals of their comparatively 

 sudden successive manifestations) ; that the organic world 

 consists, according to Mr. Galton's before-mentioned con- 

 ception, of many faceted spheroids, each of which can re- 

 pose upon any one facet, but, when too much disturbed, 

 rolls over till it finds repose in stable equilibrium upon 

 another and distinct facet. Something, it is here con- 

 tended, may be urged, in favor of the existence of such 

 facets of such intermitting conditions of stable equilib- 

 rium. 



A view as to the stability of species, in the intervals of 

 change, has been well expressed in an able article, before 

 quoted from, as follows : 1 "A given animal or plant ap- 

 pears to be contained, as it were, within a sphere of varia- 

 1 North British Review, New Series, vol. vii., March, 1867, p. 282. 



