8 HENRY H. DONALDSON 



1904 and 1909, the European frogs were similar in their general 

 form. 



The records for R. pipiens are not entered on this chart. They 

 would run a trifle below those for the European species, showing 

 that R. pipiens was more slender in its general build. This 

 character of R. pipiens taken alone would imply a slightly smaller 

 nervous system, but as we know the contrary is the case. 



TABLE 7 

 Percentage of the total length represented by the combined lengths of the leg bones 



SPECIMENS PERCENT 



R. pipiens 9 66.6 



R. esculenta 11 65 . 1 



R. temporaria 16 66 . 2 



(B) PERCENTAGE OF TOTAL LENGTH REPRESENTED BY THE 



COMBINED LENGTHS OF THE LEG BONES 



The absolute values of the percentages in this table are on 

 the average less by 3.5 than those given in the previous paper 

 (see Donaldson '08, table 2). This is the result of a change in 

 the technique of measurement. Previously the total length of 

 the frogs was taken when the animals were suspended, and under 

 this condition a certain amount of flexion persisted in the legs. 



In the present case the frog was measured when stretched 

 out on the table and lying on its ventral surface. By this treat- 

 ment the amount of flexion was reduced, and the total length 

 thereby slightly increased. This naturally reduced the percent- 

 age value of the sum of the lengths of the leg bones, the measure- 

 ments of which were made in the same way in both cases. The 

 above mentioned change in technique is the only one which has 

 been made. 



The point of importance is that the percentages are nearly 

 the same for the three species which are here compared. 



(C) THE PROPORTIONAL LENGTHS OF THE SEVERAL LEG BONES 



These are shown in table 8 in which the 1904 records have been 

 repeated and a complete series of 1909 records added. It will 

 be seen that there is no essential difference between the obser- 



