n8 



COMPARATIVE ANATOMY 



The sexes in the crayfish are separate, and the females are 

 distinguished from the males by several secondary sexual 



Fig. 26 



XVI. Third abdominal limb of the right side of Astacus ftuviatilis seen 

 from behind, cx.p, coxopodite ; />./, basipodite ; en.p, endopodite ; 

 ex.p, exopodite. XV. Second abdominal limb of the male. XIV. 

 First abdominal limb of the male. XII. Seventh thoracic limb of 

 the right side, seen from behind, z'./, ischiopodite ; m.p, meropodite ; 

 c.p, carpopodite ; p.p, propodite ; d.p, dactylopodite ; e.p, epipo- 

 dite ; br, branchial filaments ', s, coxopoditic setae. The other letters 

 as in XVI. II. The second antenna of the right side, seen from 

 below, g.g, the opening of the green gland. /. The first antenna of 

 the right side, seen from above, au, opening of the auditory organ ; 

 en.p, internal filament ; ex.p, external filament. 



characters. The abdomen of the female is decidedly broader 

 than that of the male, and the two first pairs of abdominal limbs 



