LOBSTEE OE CEAYFISH 146 



{arthrodial) membrane with a small, sharp scalpel, 

 remove each of the appendages from one side of 

 the body, beginning at the posterior end. Be 

 sure to get the entire appendage. Examine the 

 more delicate parts in water, 



a. The abdominal appendages. — Some of these 

 have already been examined. Eeview them and 

 study the others, noting in each case the structure, 

 shape, size, etc., as well as any variations from 

 the normal. Note that the stalk {jyrotopodite) 

 of each consists of two segments, the basal or 

 coxopodite and the distal or basipodite; the 

 latter forming the base, to which the other seg- 

 ments, the exopodite and endopodite, are articu- 

 lated. Notice in every case the variations in the 

 structure and shape of each segment, especially 

 of the first, second, and sixth appendages. Lay 

 pach of the appendages, posterior face upward, 

 upon a paper and draw them natural size. The 

 appendages of the sixth segment form, with the 

 telson, the tail-fin. 



h. The thoracic appendages — Can you show that 

 of the appendages on this portion of the body 

 two groups may be made^a posterior group, 

 consisting of five pairs of large appendages, and 

 an anterior group of smaller appendages near 

 the mouth ? Examine the last thoracic appendage. 

 In which direction does it extend ? Does it bear 

 an exopodite? Make out the following segments : 

 (1) the protopodite, consisting of coxopodite and 

 basipodite; (2) the endopodite, consisting of is- 

 chiopodite, meropodite, carpopodite, propo- 

 dite, and dactylopodite. Note the relative 



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