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THE AMERICAN NATURALIST [Vol. LIV 



Moreover, and this is important, the characteristics of 

 the new big claw are apparent as soon as the regener- 

 ated part begins to take shape, and even long before the 

 molt. 



The other most characteristic difference in the exter- 

 nal parts between the male and the female is found in 

 the abdomen. In the male, Fig. 2 B, it is narrow, in the 



female, Fig. 2 A, it is almost as broad as the ventral sur- 

 face of the thorax against which it is plastered. If the 

 abdomen of the male is lifted up, its anterior pair of ab- 

 dominal appendages, modified into copulatory organs, 

 can be seen (Fig. 2 B' and Fig. 3 A). In the female the 

 abdominal appendages (Fig. 2 A' and Fig. 3 B, B') are 

 entirely different, and are used to carry the eggs. The 

 external genital pores can also be seen when the abdomen 

 is lifted up; those in the male on each side of the middle 

 line are in the segment that carries the last (5th) pair 



