Donaldson, American and European Frogs. 145 



There is no good fixed point for the lower end, the one which 

 has been adopted as the cut end, obtained by cutting across the 

 leg through the knee joint at right angles to the axis of the leg 

 when it is in full extension." 



TABLE 17. 

 R. temporaria. 



Length of 



No. OF Body Weight Sciatic in 



Specimen. in Grams. mm. 



XXI 15- 10 460 



XXII 20. 15 45 .0 



XXIII 16.45 45-5 



XXIV 18.15 500 



XXV 20. So 49.0 



XXVI 24-80 53.5 



Average 19 . 20 48 . 2 



To compare with these, we have observations on four specimens 

 of R. pipiens, made by Mr. TAKAHASHi^in the Neurological Lab- 

 oratory of the University of Chicago. 



The specimens examined by Takahashi, and in which the inter- 

 nodes were studied in the same locality as that selected by Boy- 

 cott, were four in number, and the measurements made on them 

 are given in the following table: 



TABLE 18. 



Sci.iVTic Length 



No. OF Body Weight in mm.* 



Specimen. in Grams. (Calculated.) 



Ill 26 49. 



V 34 53-3 



VI 37 60.2 



VIII 63 65.8 



Average 40 57.3 



* This measurement was not made by Mr. Takahashi, but has been calculated from other data in 

 his tables. 



In accordance with Boycott's results, we should expect in 

 this series of R. pipiens, with an average sciatic length of 57.3 mm. 

 to find longer internodes than in the series of R. temporaria, with 

 an average sciatic length of only 48.2 mm., but on the contrary, the 

 internodes in R. pipiens are much shorter. To make the com- 

 parison fair however it is necessary to reduce the measurements 

 on R. pipiens to the measurements of the R. temporaria series, 



' Mr. Takahashi kindly allows me to use the data from his forthcoming paper on the internodes in 

 R. pipiens. 



