Henry H. Donaldson 



looking at the curve (Fig. 1) we note that the calculated weights vary less from frog 

 to frog than do those observed, and it thus happens that the line joining the dots 

 which mark the calculated weights threads its way between the crosses which indicate 

 the observed weights. Thus the weight of the central nervous system as calculated is 

 less irregular than that directly observed. 



Before commenting further on these results the observations on Bana virescens 

 will be presented. In the case of Rana virescens the original table contained thirty- 

 six records (Donaldson and Schoemaker, 1900, p. 120). Of these, Nos. 1, 2, 3 are at 

 once excluded as being below the 5-gram limit. Of the remaining 83, one. No. 16, 

 through some error, has a body-weight too small for its length (27.19 grams body- 

 weight; 195 millimeters length), and four more, Nos. 33, 34, 35, 36, all of them spring 

 frogs, have body weights which are manifestly too small, as is shown by the relation 

 of these records in the curve already presented (Donaldson and Schoemaker, 1900, 

 Chart I, p. 117). As there are no data for correcting these last four records, they are 

 excluded from the series here used. After these removals there remain twenty -eight 

 records taken at different times from April 14 to September 15. Some unpublished 

 work on the seasonal change in the nervous system of the frog shows that in frogs of 

 the same body-weight the weight of the central nervous system is subject to a rhyth- 

 mic change, thus altering according to the season of the year. 



During the past twelve months observations have been carried on in this labora- 

 tory with a view to following this change in some detail, and at present we have at 

 hand data which enable us to correct the weight of the central nervous system in these 

 frogs in the early and late season so as to make the observations taken at those times 

 comparable with the records from midsummer frogs. To standardize these early and 

 late records which appear in Table IV, corrections have been made in twelve instances 

 in accordance with a fixed scale. This scale is based on the following observations: 

 It appears that frogs of a given body weight, just after they emerge at the end of 

 March or the first of April, have a relatively small weight of central nervous system. 



TABLE III 



Showing the corrections made in the spring and autumn frogs, the weight of whose central nervous 



system appears in Table IV. 



23 



