EXTERNAL CHARACTERS OF BLUE WHALES 295 



in bodily proportions are taking place full physical maturity has not yet been reached. 

 It is possible, however, that the rather profound change indicated after 25 m. in males 

 and 26 m. in females is concerned with physical maturity, but more measurements 

 of these very large whales are needed before one can ascertain whether the relative 

 proportions of the body alter at this period or whether perhaps abnormally large 

 whales are abnormal in their proportions as well as in their size. 



So far only the mean values of the measurements have been considered. The 

 individual variations which occur are best examined by the method of frequency 

 curves; that is, the range of values over which each measurement varies may be divided 

 into groups and the number of individual measurements for each group may be plotted 

 out to form a curve. Owing to the fact that a certain amount of variation depends on 

 the length of the whale it is not permissible to draw curves which include all the 

 measurements which have been made. There are relatively large numbers of measure- 

 ments for males about 23 and 24 m. and females about 25 and 26 m. Thus by using 

 the bodily measurements of males measuring from 23-00 m. to 24-99 "^- ^^^ ^^^ females 

 from 25-00 m. to 26-99 m. we have enough material for the construction of curves 

 which will at least show the nature and approximate extent of the individual variations 

 which occur. One could perhaps apply a correction for length, but the value of the 

 result would hardly be sufficient to make such an enormous task worth while. 



In the following tables and in Figs. 25 to 44 this plan is carried out. In the tables 

 the range of values obtained for each measurement (still of course expressed as per- 

 centages of the total length) is divided into an arbitrary number of groups . The individual 

 readings of each measurement for male Blue whales from South Georgia measuring 

 from 23-00 m. to 24-99 m. and females from 25-00 m. to 26-99 m. are sorted out, and 

 the number which fall into each of the groups are shown. 



