MALE 



Fig. 128. — Crayfish, ventral view. The opening of the green gland (excretory 

 organ) is on the base of the antenna. The first two pairs of appendages (antenna 

 and antennule) are labeled; the third pair (mandibles), the fourth and fifth 

 (maxillae), the sixth, seventh, and eighth (maxillipeds) are not labeled (except 



the ninth to the thirteenth (five pairs of walking legs) are 

 the fourteenth and fifteenth (modified swimmerets) are 

 the transfer of sperm to the female (these swimmerets in 

 the female are much smaller or vestigial) ; the sixteenth to the nineteenth (swim- 

 merets or pleopods). The last pair of swimmerets, sometimes called the uropods, 

 together with the telson constitute the tailfin for swimming backwards. (See 

 Fig. 307.) (From Parker and Clarke: An Introduction to Animal Biology, The 

 C. V. Mosby Co.) 



the third maxilliped) 

 shown only in part ; 

 large in the male for 



