GENERAL STRUCTURE 



50: 



The common Fycnogonum is, by reason of the suppression of 

 certain liml)S, rather an outlying member than a typical repre- 

 sentative of the Order, whose common characters are more 

 strikingly and more perfectly shown in species, for instance, of 

 Nymphon. Of this multiform genus we *have many British 

 species, some of the smaller being common below tide -marks, 

 creeping among weeds 

 or clinging like Cap- 

 rellae with skeleton 

 limbs to the l)ranches 

 of Zoophytes, where 

 their slender forms are 

 not easily seen. In 

 contrast to the stouter 

 body and limbs of 

 Pycnogonum, the whole 

 fabric of Xyvvphon 

 tends to elongation ; 

 the body is drawn out 

 so that the successive 

 lateral processes stand 

 far apart, and a slender 

 neck intervenes be- 

 tween the oculiferous 

 tubercle and the pro- 

 boscis ; the legs are 

 produced to an amazing 

 length and an extreme 

 degree of attenuation : 

 " mirum tam parvum 

 corpus regere tam 

 magnos pedes," says 

 linnaeus. Above the 

 base of the proboscis are a pair of three -jointed appendages, 

 the two terminal joints of which compose a forcipate claw ; 

 below and behind these come a pair of delicate, palp -like 



bi'evissimis compositi, iingue valido termiiiati. Ex descriptione patet insectum 

 hoc a generibus antea notis omnino diffeiTe, ideoque novum genus, quod e crebiis 

 artieulationibus Pycnogonum dico, constituit." The confusion between Cyamus 

 and Pycnogonum seems to have arisen with Job Baster, 1765 ; cf. Stebbing, Knotv- 

 ledgc, February 1902, and Challenger Reports, " Amphipods," 1888, pp. 28, 30, etc. 



Fig. 263. — Dorsal view of Nymphon brevirostre, 

 Hodge, X 6. Britain. 



