12 HENRY H. DONALDSON 



TABLE 10 

 Weight of the central nervous system in grams. Averages from groups of three 



WEIGHT OF 

 BODY WEIGHT CENTRAL, 



NERVOUS SYSTEM 



14.9 .1040 



R. pipiens < oq o 



23.2 .1256 



.1463 



R. esculenta 1904. 



R. esculenta 1909. 



R. temporaria 1904 < 9 o q 



43.2 .1674 



15.9 .0890 



22.0 .1142 



35.0 [2] .1402 

 40.2 .1498 



23.4 .1077 



32.1 .1258 

 43.8 .1524 



55.2 [2] .1724 



C 15.9 .0929 



23.1 .110S 



.1213 

 [31.3 .1323 



f 18.0 [4] .0899 



1 25.2 .1053 



R. temporaria 1909 i 26.9 .1144 



29.5 .1212 

 [34.8 .1380 



If this observation applies, as it probably does, to the European 

 species, then the differences in weight as shown in chart 2 

 are susceptible of the following explanation : 



The esculenta of 1904 were examined August 1 — 5, when it 

 may be assumed that the nervous system of R. esculenta had 

 attained approximately its maximal seasonal weight. In 1909 

 the examination was from July 5-7, or some four weeks earlier. 

 Under these circumstances, a somewhat smaller weight was to 

 be expected, and the records show this. 



The temporaria of 1904 were examined July 11 and 12, before 

 the central nervous system had reached the maximum for the 

 season. 



In 1909 the examination was from August 17 to 21, or some 



