6 PYCNOGONIDA. 
Linné: cauda; O. Fabricius: cauda; Latreille: le dernier segment du corps; Lramarek: 
abdomen; Leach: abdomen; Savigny: abdomen; Johnston: abdomen; Milne-Edvards: abdomen; 
Erichson: Hinterleib; Krøyer: Bagkrop, abdomen; Wilson: abdomen; Dohrn: Hinterleib; 
Bøhm: Abdomen; Hoek: abdomen; Adlerz: abdomen; Hansen: Bagkrop (abdomen); Sars: Hale- 
segment (segmentum caudale). 
The appellation of this part of the trunk was in the early authors (Linné and O. Fabricius) 
simply cauda, tail; but Latreille having pointed out that it was a part, a segment, of the trunk 
itself, the first name was displaced by the appellation abdomen and the translations of it (Hinterleib, 
Bagkrop), which was adopted by all authors until Sars, the opinion being, I suppose, that it corre- 
sponded to the abdomen of the other Arthropoda, especially that of the Insects and the Arachnida. 
Sars, as it were, has meant to adopt the old name of tail, but on account of the prevalent aversion 
to this appellation, he has altered it to the mediate one of caudal segment, and I have followed him 
partly of similar reasons. — As to its development the caudal segment is the hindmost part of the 
hindmost principal division of the embryo, and until a far advanced stage in the larval development 
it forms a hindmost, gradually more protruding, process of the fourth segment of trunk. If upon the 
whole it is separated from this segment by a dermal suture, this does not take place until the third 
larval stage. It never bears limbs, but the intestinal canal opens in the end of it with a weak squir- 
ting apparatus. Thus the caudal segment no doubt belongs to and makes the hindmost 
part or segment of the same principal portion to which the four preceding seg ments 
belongs; it is no separate part of the body, different from the foregoing segments of the trunk, no 
abdomen in contradistinction to a thoracical part, lying before it. The caudal segment can be pro- 
portionally very long, almost as long as the body, and then it is also well separated from the fourth 
segment of the trunk and very slender; there is no trace of division in joints, not even in ZeZzes 
(Eurycyde), as has been maintained. On the other hand this segment may also be quite small, as it 
were, rudimentary, as I know from a not described genus among the collections, which the Smithsonian 
Institute has given me for examination. 
Lateral process of the body for the insertion of the ambulatory legs (fprocessus 
corporis lateral), fig. 1 pc/. 
Sars: Legemets Sidefortsatser (processus laterales corporis) til Fæste for Gangfødderne. 
These processes of the body and the ambulatory legs attached to them, are structures charac- 
teristic of the Pycnogonida, as they are not formed by germinating or growth of a particular cellular 
group but, as is distinctly seen from my drawings of the embryo, by a bag-like constriction of the 
ectoderm, in the same manner as the embryonal limbs (the chelifori and embryonal legs). They are 
in reality only parts of the body, and so it will easily be understood, that the intestinal canal and 
the sexual glands can continue far into the ambulatory legs as processes of the body. 
Cheliforus (c4e/zforus), fig. 1 chf and 2 a. 
Linné: palpi; O. Fabricius: palpi; Latreille: mandibules; later (Régn.an. éd. II): antenne- 
pinces; Leach: mandibulæ; Savigny: pedes secundi; Lamarck: antennules; Johnston: mandib- 
les; Milne-Edwards: pattes-måchoires; Erichson: erstes Kieferpaar or Scherenkiefer (Mandibeln); 
Krøyer: Saxe (antennæ cheliformes); later Kindbakker (mandibulæ); Bøhm: Kieferfuihler; Wilson: 
