Hybridization between Robertsonian karyotypic races of the common shrewSorex araneus

Summary British common shrews of the Aberdeen, Oxford and Hermitage Robertsonian karyotypic races were hybridized successfully in captivity. Hybrids, both simple Robertsonian heterozygotes and double Robertsonian heterozygotes with monobrachial homology, have been identified in an area of contact between the Oxford and Hermitage races. The relative fertility of these two types of hybrid is considered.I thank Dr. C. E. Ford F. R. S., Prof. F. W. Robertson and Dr A. E. Douglas for reading earlier drafts of this paper, Prof. F. W. Robertson, Dr J. R. K. Savage and Dr J. R. Clarke for laboratory facilities, Mrs J. E. Evans for technical assistance and S.E.R.C. for financial support.