98 THE FRESH-WATER CRAYFISH— THE CAPE CRAWFISH 



branch or endopodite. The two uropods, together with the median 

 telson, form the five-lobed tail, the swimming paddle. 



(6) The pleopods are attached on each side of the 1st to 5th segments. 



In the female the first pleopod is more or less vestigial. In the male the 

 first and second pleopods form incomplete tubes and act as copulatorj' organs. 

 The coxopodite is present, but there is no exopodite and the basipodite appears 

 fused with the endopodite. A typical pleopod — e.g., the second — consists of a 

 basal segment or protopodite, composed of coxopodite and basipodite, bearing 

 an endopodite whose proximal joint is enlarged and an exopodite in the form 

 of a jointed rod. 



[In Jasus the pleopods are attached to the second, third, fourth, and fifth seg- 

 ments. In the female the first pleopod is com/posed of a single basal protopodite 

 bearing an endopodite and an exopodite which are equally developed. The second, 

 third, and fourth have the endopodite in the form of a rod. In the male the endo- 

 podite is absent, all the pleopods being similar. \ 



Draw a uropod, and the first and third pleopods. 



B. The Eight Thoracic Appendages of the Left Side. 



These are divided into the five walking legs and the three maxillipeds. 



(a) The walking legs or pereiopods are attached to the side of the thoracic 



region. 

 Each leg is composed of a basal two-jointed protopodite (the coxopodite and 

 the basipodite) and a five-jointed endopodite (the ischiopodite, meropodite, 

 carpopodite, propodite, and dactylopodite). There is no exopodite. A podo- 

 branch and an epipodite are attached to the coxopodite of the first four walking 

 legs of each side. The first pereiopod of each side ends in a large pincer-like 

 claw or chela, formed by the dactylopodite working against a prolongation of 

 the propodite, and is therefore called the cheliped. 



In the second and third pereiopods of each side there is also a claw present, 

 but it is much smaller than that of the first walking leg. Note the genital 

 apertures. 



\In Jasus the chela is UMtally present on the last pair of pereiopods in the female. ^ 

 (&) The Maxillipeds. 



(i) The third maxiUiped is attached just anterior to the first walking leg. 

 It is composed of a basal two-jointed protopodite (the coxopodite 

 and the basipodite) bearing a five-jointed endopodite (the ischio- 

 podite, meropodite, carpopodite, propodite, and dactylopodite) and a 

 smaller exopodite ending in a feeler-like flagellum. A podobranch 

 and an epipodite are attached to the coxopodite. 

 (ii) The second maxiUiped resembles the third, but is smaller. [In Jasus 

 the endopodite is only four-jointed, the ischiopodite and meropodite having 

 fused together.^ 

 (iii) The first maxiUiped differs from the other two. The coxopodite and 

 basipodite are broad thin plates, while the endopodite is short and 

 only two-jointed. The unjointed portion of the exopodite is long. 

 An epipodite is present, but it has no giU. [In Jasus the endopodite is 

 only single-jointed.] 



