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[VOL. I. 



twenty-four pairs. 1 Sedgwick's statement that the males have 

 the lowest number of legs holds good here in every case except 

 one. All those specimens having twenty-nine, twenty-eight, or 

 twenty-seven pairs of legs were females, while all those with 

 twenty-six, twenty-five (with one exception), or twenty-four 

 pairs were males. 



The number of these appendages is fixed at birth, as is also 

 the case with P. Edwardsii, as Sedgwick has shown, and the 







FIG. i. 



number of appendages of the mother is not necessarily trans- 

 mitted to the embryo. From a mother with twenty-seven pairs 

 of legs, three embryos were removed, each with twenty-eight 

 pairs of appendages ; and again from a mother with twenty- 

 eight pairs of legs three embryos were removed, the two most 

 mature of which had twenty-five pairs, while the less mature 

 one had twenty-six pairs. These last three specimens had 



1 Dr. Wheeler mentioned in his paper one specimen with twenty-three pairs of 

 appendages ; this I was unable to find after carefully reexamining all the males. 



