74 



JURG OTT 



hybrids were found. The two groups thus are reproductively isolated. More- 

 over, the large karyotype différences make the fertility of hybrids most 

 unlikely; 



3. No différence between zone I and II exists in skull length for both species. 

 The skull length of S. gemellus (19.63 ± 0.07 mm; n = 24) is less than that 

 of S. araneus (19.98 + 0.05 mm; n = 49), and the différence is statistically 

 significant. Two km below zone I S. gemellus were caught exclusively, whose 

 skull length is even less (19.28 ±0.11 mm; n = 13); 



4. Tail lengths of animais from zone II were compared. 



S. gemellus : 44.8 + 0.4 mm; n = 12 v 

 S. araneus : Al A + 0.8 mm; n = 7. 



The différence is statistically significant (p < 0.01). The relative values 

 do not change the resuit. 



The différences in length of skull and tail do not permit unequivocal differen- 

 tiation of the two species. Preliminary examination of the skulls suggests the 

 possibility that a completely differentiating complex characteristic can be found. 

 A more detailed analysis of the skull measurements is in préparation. 



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