330 
SEXUAL SELECTION. 
Part II. 
In the higher crustaceans the anterior legs form a 
pair of chelae or pincers, and these are generally 
larger in the male than in the female. In many species 
the chelae on the opposite sides of the body are of 
unequal size, the right-hand one being, as I am in- 
Pig. 4. Anterior part of body of Callianassa (from Milne-Ed wards), showing the unequal 
and differently -constructed right and left-hand chelae of the male. 
N.B. — The artist by mistake has reversed the drawing, and made the left-hand chela 
the largest. 
Fig. 5. Second leg of male Orchestia Tucuratinga (from Fritz Muller). 
Fig. 6. Ditto of female. 
formed by Mr. C. Spence Bate, generally, though not 
invariably, the largest. This inequality is often much 
greater in the male than in the female. The two chelae 
also often differ in structure (figs. 4 and 5), the smaller 
one resembling those of the female. What advantage 
