504 PYCNOGONIDA 



limbs of five joints ; and lastly, on the ventral side, some 

 little way behind these, we find the ovigerous legs that we have 

 already seen in the male Pycnogonum, but which are present in 

 both sexes in the case of Nymplion. At the base of the claw 

 which terminates each of the eight long ambulatory legs stands 

 a pair of smaller accessory or " auxiliary " claws. The genera- 

 tive orifices are on the second joint of the legs as in Pycnogonum, 

 but as a rule they are present on all the eight legs in the female 

 sex, and on the two hindmost pairs in the male. One of the 

 Antarctic Nymphonidae (Pentanymphon) and one other Antarctic 

 genus less closely related (Decolopoda) have an extra pair of legs. 

 No other Pycnogon, save these, exhibits a greater number of 

 appendages than Nymplion nor a less number than Pycnogonum, 

 nor are any other conspicuous organs to be discovered in other 

 genera that are not represented in these two : within so narrow 

 limits lie the varying characters of the group. 



In framing a terminology for the parts and members of the 

 body, we encounter an initial difficulty due to the ease with 

 which terms seem applicable, that are used of more or less 

 analogous parts in the Insect or the Crustacean, without warrant 

 of homology. Thus the first two pairs 

 of appendages in Nympli07i have been 

 commonly called, since Latreille's time, 

 the mandibles and the palps (Linnaeus 

 had called them the palps and the 

 antennae), though the comparison that 

 Latreille intended to denote is long 

 abandoned ; or, by those who leaned, 

 with Kroyer and Milne - Edwards, to 

 the Crustacean analogy, mandibles and 

 maxillae. Dohrn eludes the difficulty 

 Fro. 264. Xymphon brevi- j iy denominating the appendages by 



rostre, Hodge. Head, from ' 



below, .showing chelo- simple numbers, I., II., III. . . . VII., 



phores, palps, and oviger- and thig metho( J hag itg own advantages ; 

 ous leg. 



but it is better to frame, as Sars has 



done, a new nomenclature. With him we shall speak of the 

 Pycnogon's body as constituted of a trunk, whose first (composite) 

 segment is the cephalic segment or head, better perhaps the 

 cephalo thorax, and which terminates in a caudal segment or 

 abdomen ; the " head " bears the proboscis, the first appendages 



