PYCNOGONIDA. 



onal legs to the pairs of limbs found in the imago. In the genus Pycnogonum the first pair of ambu- 

 latory legs, according to this, would be called Extrem. VI, the first five pairs of limbs having to be 

 subtracted. 



The foregoing list and figure apply to the grown larva, the young, and the imago; with 

 regard to the young larva the following short list together with the figure of this larva, seen from 

 the under side, must suffice. 



a. Cheliforus. 



6. First pair of embryonal legs. 



c. Second pair of embryonal legs. 



d. Proboscis. 



e. First pair of ambulatory legs. 



f. Second pair of ambulatory legs. 



Fig. 2. Nymphon robustum. Larva. 



I shall now proceed to notice the outer organs, giving a short description of each as well as 

 the reason of the terms I have chosen, and at the same time I shall quote as synonyms the corre- 

 sponding appellations by the chief earlier authors. 



Proboscis (rostrum}, fig. i r, and 2 d. 



O. F a b r i c i u s : tubulus v. rostrum ; L a t r e i 1 1 e : tuyau on siphon d'une seule piece ; later (Regn. 

 anim. ed. II): bouche; Leach: os tubulosum, or rostrum; Savigny: premier anneau du corps allonge 

 et rempla9ant la tete (vestiges de machoires); Johnston: rostrum; Milne-Edwards: tete; Erich- 

 son: Zuuge; Kroyer: Nseb (in the larva), later: Snabel (rostrum); Wilson: proboscis, or rostrum; 

 Dohrn: Schnabel; Bohm: Rostrum; Hoek: trompe (proboscis); Adlerz: snabel; Hansen: Snabel, 

 or Proboscis (proboscis); Sars: Snabel (proboscis), or Mundsegment 



The proboscis is the conical or almost cylindrical organ protruding from the anterior margin 

 of the bod}-, or from the lower side of it; it is always large or especially so in proportion to the body, 

 and has at the point a trilobate mouth, leading to the trilateral pipe, which is closed behind by a 

 kind of plait, protruding to a rather sharp angle and working as a filtering apparatus. The pro- 

 boscis is commenced at a very early stage of the embryonal life (pi. i , fig. i) as a ball or tubercle 

 without any trace of mouth , contemporary with the embryonal limbs (the chelifori and embryonal 

 legs). It is 110 segment or metamere, and still less corresponding to, what in other animals is called 

 the head, or to part of the head. Neither can it in any way be siipposed to have arisen by a coal- 

 escing of guathites. 



First segment of trunk (scgmentum co rporis primum), fig. i c 1 . 



O. Fabricius: caput et thorax v. primus articulus corporis; Leach: segmentum anticum; 

 Latreille (Regn. an. ed. II): le premier segment du tronc; Johnston: the anterior segment of 

 thorax; Erichson: Kopf; Kroyer: Oiering og f0rste Brystring (annulus ocularis et annulus thora- 



