1894.] certain External Parts of Palsemon serratus. 237 



Values of Galton's Function (r) for Pairs of Organs in the Common 



Prawn. 



(The Roman numerals refer to the list of organs measured given 



above.) 



An examination of these values shows that, as might be expected, 

 the highest degree of correlation exists between the paired organs, 

 viz., between the right and left squames, 0'94 ; between the right and 

 left exopodites of the 6th pair of swimmerets, which, with the 

 telson, form the propelling organ of the prawn, 0'86 ; between the 

 distances of the spines on the telson from its posterior end, 0'76. 



Next, we observe that a strong correlation obtains between the 

 terga of adjacent abdominal segments; their values range between 

 O58 and 0'71 ; while those of segments that do not lie next each 

 other range between 0'47 and O61. A considerable fall occurs in 

 the degree of correlation between the telson and the segments of the 

 abdomen it varies from 0'26 to 0'29, except in the case of the 6th 

 abdominal segment, which lies next to the telson, when the value 

 rises to O51. It is interesting to note that Professor Weldon found the 

 corresponding value for the telson and 6th abdominal tergam in the 



