﻿rVCNOGONIDA. ,, 



based on the fact, whether the foremost limbs, as well the embryonal limbs as the imaj^^inal limbs, 

 continue the t\pical development, or their development is checked on an earlier or later stage, whetlier 

 they go through a slighter or more marked retrograde development, or how long they are kept upon 

 the wliole. How small a systematic importance these foremost limbs have, nuiv be seen, among other 

 things, by the fact that a pair of these limbs may be kept in one sex, while it is thrown off in the 

 other, and thus the reason of the keeping seems only to be purel\- biological; m<M-eo\-er the keeping 

 or the throwing off takes place without producing or corresponding to an\- other difference in striK- 

 ture between the two sexes. To make such organs the base of the division into orders, seems to me 

 very inifortunate, and it is only for want of better characteristics that I lia\-e used these limbs as 

 family distinctions — in realit\- tlie\' are onh- of value as generic distinctions. Therefore I do not 

 think it necessary to enter upon a detailed valuation of the orders that have been put up. 



Among the different systems those of Wilson, S\u. P\'cnog. New. Engl. iSj-8, and Hoek, 

 Rejjort Pycuog. , iS8i, and Nouv. ctud. Pycuog. iSSi, seem to me to be the best. The svstem of 

 Wilson must be said to be well worked out, but on the other hand it is rather artificial, too much 

 stress being laid uj^ou characteristics taken from the au.xiliary claws and the niunber of joints in the 

 palps and the ovigerous legs. The system of Hoek in Report P\cnog. is merely a grouping of tlie 

 genera without an\" real arranging of these genera inside the families. In his s\-stem in Xouw etud. 

 Pycuog. p. io6 the number of families has been reduced to four, and these four correspond to my 

 system, as well with regard to the appellations as, chiefh', to the characterization, and the genera 

 contained in each of them; it is however to be noted that the genus Pallniopsis has by Hoek been 

 referred to Phoxicliilidcc ^ but by me to Xyiiiplioiiidu-. The genealogical table gi\-en by Hoek with 

 its extremely problematic primitive form ArchipycnogoiiiDii^ I am not able to appreciate rightly. 



The system I ha\-e used, is more particularly intended for the Pycnogonida brought home by 

 the Ingolf expedition with the object of its also being able to comprise the new species. 



I. Fam. Nymphonidae. 



Corpus manifeste in segmenta partituni. 



Rostrum c\lindricum, iuflexibile, libratum \'el nutans. 



Chelifori expleti, chela instructi. 



Palpi vel expleti, \el innniuuti, \el deficientes. 



Pedes oviferi in utroque se.xu. 



The trunk distiuctl}' segmented. 



The proboscis cylindrical, infiexible, horizontal, or directed obli(|UeK- downward. 



The chelifori well de\-eloped (with chela). 



The palps well de\'eloi)ed, or rudimeutar\', or wanting. 



Ovigerous legs present in both sexes. 



As it will appear from the family-diagnosis, this family comprises the species belonging as 

 well to Nyiiiphoii as to PallriK^ that is tt) say, the families Xyiiiphoiiidcr and PoUoiida- of Sars. An 



Tlie iMgiill-lrxpcililioii. III. I. 5 



