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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 95 



had metamerically repeated gonads with individual segmental outlets. 

 The ovaries and testes, however, which are formed during larval 

 metamorphosis, are said to take first the form of a pair of simple 

 tubes united with each other above the alimentary canal ; later they 

 acquire the characteristic branched adult structure by the extension 

 of lateral diverticula into the leg bases above similar diverticula of 

 the alimentary canal. The development of an outlet on each leg, there- 

 fore, may be merely the result of the great reduction of the body. 



Fig. 7. — Pycnogcnida : position of the genital openings. 



A, Chaetonyviphon spinosum, female, ventral view of body and bases of legs, 

 with four pairs of gonopores (Gprs) on the second leg segments. B, same, base 

 of leg, anterior view, showing position of gonopore. C, same, mesal view of 

 gonopore. 



bl, leg-bearing body lobe; Chi, chelicera; Fm, femur; Gpr, Gprs, gonopore, 

 gonopores ; iL, first leg ; 2L-5L, ambulatory legs ; Mth, mouth ; Pat, patella ; 

 Pdp, pedipalp; Prb, proboscis; i, 2, 3, three small proximal leg segments. 



The writer has been unable to find any information on the mode of 

 origin of the genital ducts in the Pycnogonida, but since the segment 

 of the genital openings is not fixed in the arthropods generally there 

 is no reason why a condition of multiple openings might not be a 

 secondary development. It should be observed, furthermore, that 

 the position of the pycnogonid gonopores on the second segments of 

 the legs does not conform with that of the genital apertures in other 

 arthropods having the gonopores on the legs, since in the latter (Crus- 

 tacea, Diplopoda) the apertures are on the bases of the first leg seg- 

 ments. In any case, the pycnogonids are in no sense primitive arthro- 

 pods, since they are highly aberrant chelicerates, and have no similarity 



