THE CRAWFISH. 115 



the specialized two-parted tips of the appendages of the 

 sixth abdominal segment. 



Dissection. The remaining parts to he mentioned are 

 best seen upon dissection. The crawfish is best dissected 

 under water. 1 Pin it to the bottom of your dissecting 

 pan, with the right side of the body upward, and the head 

 from you. Fasten one pin through the base of the ros- 

 trum, draw the body out full length, and fasten another 

 pin through the left appendage of the sixth abdominal 

 segment. Cover the specimen with water, dissect slowly 

 and carefully and as directed, and change the water as 

 often as it becomes cloudy. 



I. Appendages. Begin with the series of appendages, 

 and, for convenience in dissecting, proceed from the pos- 

 terior end forward. Remove each appendage of the right 

 side in order, and be very careful to get each one off 

 entire. Preserve all in their proper order for drawing. 



The absence of appendages from the terminal segment 

 has already been noted. The broad finlike character and 

 the extension backward of the appendages of the sixth 

 abdominal segment have also been noted. The smaller 

 appendages of the remaining five abdominal segments are 

 extended forward, close under the abdomen, and are called 

 swimmerets. Each consists of a short pedicel of two seg- 

 ments, with a pair of jointed and fringed filaments at the 

 tip. The swimmerets of the fifth, fourth, and third ab- 

 dominal segments are very similar, but those of the second 

 and first segments . are reduced and smaller, or the first 

 entirely wanting in the female, while in the male they 

 are specialized, bent forward strongly under the thorax, 

 and variously forked, hooked, or twisted at the tip. 



The next five pairs of appendages are the legs, and 

 belong to the thorax. Before removing these, it will be 



* See Appendix, p. 283. 



