THE APPENDAGES, THEIR INTERRELATION AND FUNCTION 3>7 



maxilla, it bears no endites and no setae. The part of the limb which Skogsberg considered as the 

 endopod bears a single long brush-seta extending forward towards the mid-line of the animal 

 (Figs. 7 and 12). The exopod of the appendage (Figs. 7, 10 and 12) has four articles, the proximal 

 being the longest, the distal, as in the case of the maxilla, being the shortest. In the female, there are 

 two distal claws and a seta, similar to those of the maxilla, but in the male there are three extremely 

 long natatory setae, which can curve upwards as far as the hinge-line of the carapace. Further setae 

 on the exopod may be described as similar to those of the maxilla. Projecting ventrally there is a 

 single apical seta on the inner face of the protopod in series with two further setae on the first article 

 and one on the third article. Projecting towards the mid-line from the inner face are three setae on 

 the first article, one on the second and one on the third. There is only one seta extending outwards 

 from the limb, on the first article of the exopod. In addition, however, there are further setae (not 

 represented) on the maxilla— a dorsal distal seta on the first article of the exopod and a dorsal medial 

 seta on the third article. 



Movement of the limb would seem to resolve into an antero-posterior movement of the protopod 

 and a dorso-ventral extension and flexure of the exopod. The ventral flexure of the limb may not be 

 as great as that of the maxilla but the dorsal extension is greater. 



The epipods of these appendages beat in conjunction with those of the maxillae. It is possible that 

 the limbs themselves could take part in collection of food, but the enormously elongate apical setae 

 in the male are strongly suggestive of some function of locomotion in this sex. 



side of the 

 only setae 



Second trunk-limbs (Figs. 2 & 13) 

 The second trunk-limb (Fig. 2, tr 2 , Fig. 13) is very short with three articles. It arises at the 

 body just behind the first trunk-limb. At rest it is directed dorsally and posteriorly. The 

 arising from this appendage are two apical setae, one of which is very long, 

 extending to the posterior dorsal margin of the carapace and the second of 

 which is only half the length. Muller (1894) described the movement of this 

 appendage in some detail. Apparently, as its structure suggests, it is extremely 

 mobile; it can be flexed or rotated freely. 



The immediate function which comes to mind in the case of these limbs, 

 with their position high on the side of the body of the animal and extreme 

 mobility, is that of cleaning. Muller, however, pointed out that these limbs 

 cannot reach the epipods of the maxillules and maxillae, the most obvious 

 structures to require cleaning. Furthermore he described how these structures 

 are self-cleaning. Muller was, in fact, not able to observe the second trunk-limb 

 performing any definite function. Some doubt must thus remain about this. 



Furca (Figs. 2 & 7) 

 The furca of the Myodocopa is so well known as to need little more than brief 

 mention. Each furcal plate bears eight claws, an anterior group of four large Fig. 13. C. borealis anti- 

 ones and a posterior of four smaller ones. All eight claws radiate outwards g£ ^ £££?""* 

 from the furca, the most anterior one, which arises from the anterior border 



of the furcal plate, pointing markedly anteriorly. The more posterior claws point slightly back- 

 wards. All the claws are bipectinate on their posterior margins. Antero-posterior flexure of the 

 trunk of the animal and hence antero-posterior movement of the caudal furca, can be considerable. 

 Thus the trunk may be stretched out straight posteriorly to extend the caudal furca through the 



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