200 abstracts: zoology 



simple hybrid with either parent were practically identical with the 

 preponderant parent in the means and ranges of the characters studied. 

 The simple hybrids showed little or no evidence of dominance in 

 the Fi nor of segregation in definite ratios in the F2, the Fo distribu- 

 tions having been, practically without exception, unimodal. None 

 of the hybrid plants appreciably exceeded the combined parental 

 ranges in respect to any character, while in the F2 of wider crosses, 

 e. g., between Egyptian and Upland cottons, extraparental characters 

 are abundantly expressed. 



The second and third generations of the simple hybrids, as compared 

 with the parents after two and three generations of selfing, were not 

 more variable than the more variable Gila parent and were only a little 

 more variable than the Pima parent. This points to the possibility of 

 obtaining relatively stable and uniform recombinations of the desira- 

 ble characters of varieties belonging to the same general type, while 

 breeders have found it well-nigh impossible to "fix" wider crosses 

 such as those of Egyptian (or Sea Island) with Upland cotton. 



T. H. K. 



ZOOLOGY. — The criterion of suhspecific inter gradation in vertebrate 

 zoology. Harry C. Oberholser. Science, n. ser. 48: 165-167. 

 1918. 



Intergradation is now generally accepted as the criterion of zoological 

 subspecies. What constitutes subspecific intergradation, however, 

 seems to be still debatable, particularly that kind of intergradation 

 represented by individual variation in a form geographically separated 

 from all other races of the species. This is illustrated by the case of 

 Aphelocoma calijornica and Aphelocoma calif ornica sumichrasti, the ranges 

 of which are widely separated by intervening forms which have not, 

 in all cases, direct geographic intergradation, although the individual 

 variation in the latter overlaps that in the former. If in such cases 

 we are to consider the two forms as distinct species, we must, to be 

 consistent, treat all island and isolated alpine forms as distinct species 

 however slightly and inconstantly they may be differentiated. The 

 logical course, however, seems to be to consider this individual varia- 

 tion as equivalent to contiguous geographical intergradation, and thus 

 regard individual variation as one of the chief criterions of subspecific 

 intergradation. H. C. O. 



