NO. 14 INSFXT AHDOMKX SNODGRASS 2T, 



all the somites have appendages, therefore, the gonopore lies between 

 the penultimate pair of legs (A) ; but in some forms the legs of the 

 last somite or of the last two somites are absent, and in such cases 

 the gonopore is either between (B) or behind the last pair of legs 

 present. The opening is usually situated on a small papilla, which 

 may take the form of a short conical or tubular projection serving as 

 a penis or as an ovipositor. Copulation in the Onychophora ap- 

 parently has not been observed. Males in confinement have been 

 recorded (Sedgwick, 1885) as depositing the spermatophores at ran- 

 dom upon the outside of the female's body, but since the spermatozoa 

 are found in the female within the oviducts and the spermathecae it 

 would seem that normally the spermatophores must be transferred 

 from the male directly into the genital opening of the female. 



III. PYCNOGONIDA (PANTOPODA) 

 The body of a pycnogonid (fig. 7 A) consists principally of the 

 appendage-bearing region composed of seven or eight segments, some 

 of which are united ; anteriorly, however, there is a large proboscis 

 (Prh) with the mouth at its extremity, and posteriorly a rudimen- 

 tary, unsegmented abdomen (Ab) bearing the anus. The first and 

 second appendages {Chi, Pdp) evidently correspond with the che- 

 licerae and pedipalps of other Chelicerata. The following appendages 

 are leglike in form and have an ambulatory function, except the 

 slender first pair {iL), which are used by the male for carrying the 

 eggs, and which are much reduced or absent in the females of some 

 species. The usual number of legs, including the " ovigerous legs ", 

 is five pairs, but in a few genera there are six pairs. The fifth legs 

 are the seventh pair of postoral appendages, and thus correspond with 

 the chilaria of Xiphosiira (fig. 8 A, Chi). The sixth legs, therefore, 

 when present, are represented in the Xiphosurida by the broad plate- 

 like operculum of segment VIII, on the posterior surface of which 

 are the genital apertures. 



The genital openings of the pycnogonids in each sex are situated 

 ventrally on the second segments of the legs (fig. 4 A, Gprs, B, C, 

 Gpr). Typically there is a gonopore on each of the ambulatory legs, 

 but the openings may be limited to the last two or three pairs, and in 

 two genera they occur only on the terminal legs. During mating the 

 male grasps the female, either dorsally or ventrally, and the eggs 

 apparently are fertilized externally as they issue from the female. 

 The fertilized egg masses are carried by the male attached to his 

 ovigerous legs. 



The segmental duplication of the gonopores in the Pycnogonida 

 might seem to give support to the view that the primitive arthropods 



