65:^ 



is more closely allied with tiie European F^andfrog than with the 

 Waterfrog. The similarity in the modus of living with the latter has 

 no iiifliience in this respect. The following calculations of/; for some 

 Aniphibia prove indeed that other factors are predominant there. 



Valuable evidence for the calculation of the exponent of correlation 

 for this class might be obtained from the Japanese or the American 

 Gigantic Salamander (Megalobatrachus maximns and Cryptobranchus 

 Alleghaniensis). The former is certainly more than 100 times heavier 

 than the Spotted Landsalamander, and surpasses the Crested or Great 

 Newt more than 400 times in weight. But, as far as I know, this 

 evidence does not exist. 



If we admit for Amphibia the same exponent of correlation as 

 for the three highest classes of Vertebrates, then we tind the following 

 values for k. 



S 



1. Waterfrog (Rana esculenta) (aver.) 



2. Leopard Frog (Rana virescens) (5) 

 J. Bullfrog (Rana Catesbyana) (6) 



4. Landfrog (Rana fusca) (aver.) 



/. Common Toad (Bufo vulgaris) (aver.) 



6. Shackletoad (Alytes obstetricans) (aver.) 



7. Treefrog (Hyla arborea) (aver.) 



5. Spotted Landsalamander (Salamandra maculosa) (1) 

 9. Great Water-Newt (Triton cristatus) (2) •) 



44.5 G. 

 73.35 

 244.4 

 53.0 

 44.5 



7.7 



4.8 

 24.88 



7.46 



0.106 G. 



0.153 



0.204 



0.088 



0.073 



0.041 



0.043 



0.047 



0.019 



0.0127 

 0.0138 

 0.0094 

 0.0095 

 0.0087 

 0.0131 

 0.0179 

 0.0078 

 0.0062 



The comparatively high value of k in the two first mentioned 

 species, likewise in Alytes obstetricans and especially in the 

 Treefrog, has evidently some relation with a higher organisation of 

 the nervous system, and not with the surroundings in which the 

 animals live. Rana Catesbyana lives, as likewise R. esculenta and 

 R. virescens, in water, ranks however near to R. fusca, the Landfrog. 

 The deviation of k in this respect is in the latter analogous with 



^) N'. 1, 4, 5, 6, 7 are borrowed from Lapicque and Laugier (I.e.) ; 2 and 3 

 from Donaldson (Journal of Comparative Neurology. Vol. 10. (1900), p. 121 [the 

 5 largest Rana virescens ('^)], Journal of Comparative Neurology. Vol. 8. (1898) 

 p. .330. Decennial Publications. Chicago. Vol. 10. (1902), p. 7 [the G largest Raua 

 Catesbyana] ; 8 and 9 from Welcker-Brandt (I.e., p. 57 and 58). 



42 



Proceedings Royal Acad. Amsterdam. Vol. XVI. 



