COPEPODA 



have been described, but also the younger stages, as far as they showed features of any interest The 

 descriptions are as a rule rather long, partly on account of the new characters, which are taken into 

 account, partly because it often struck me, that existing descriptions were often too wanting in details 

 for a sure definition of nearly related species. 



Under each species is found a list of synonymy, which I have tried to make as complete as 

 possibly for the }ears after the publication of Giesbrecht's classical paper; for each species I have 

 given the measurements of each examined stage. 



After the description is added a few words of the variations and parasites, if any have 

 been observed. Under occurrence I have only given my personal observations, but under distribution 

 I have dealt with the facts, previously published, relating to the occurrence of each species withiu 

 as well as outside the explored area. Under remarks the whole systematic position of the species 

 is discussed. 



On variation and parasites. 



In a good many species viz: Rhincalanus iiasufus, Eucalanus elongatus, Paracalanus parvus^ 

 Pseudocalaniis minutus, Chiridius armatiis, Gaetanus Kruppi., G. pileatus and G. latifrous, E^tchirella 

 rostrata and curticauda^ Euchate tonsa and barbata and Scaphocalanus magnus variations of different 

 kinds were observed; most common is variation in a rudementary fifth pair of legs and in the struc- 

 ture of the setae of the furcal branches; several of the variations are probably due to traiunata and 

 regeneration, others certainly represent a kind of atavism. To study the whole question of variation 

 within the Copepods or to collect all the published facts (cf. Wolfenden and Steuer) does not lie 

 within the frame of this paper. But as such facts are rather scarce, and as they may be important 

 for a future student of these topics, it seems to me to be the duty of each observer to make his per- 

 sonal observations known, even if they are fragmentary. Negative statements are seldom of much 

 value; but nevertheless I think it rather curious, that abnormal segmentation, which is fairly common 

 in the Arachnids, Insects and Annelids, was never met with in any of the examined, I think several 

 thousand, Copepods; to my knowledge no case of abnormal segmentation has been observed in auy 

 of the Crustacea. 



In several species parasites of different kinds have been observed ; I refer to the description 

 of Rhincalanzis iiasiitus, Ghiridiiis aniiahis^ Gaidius tcnuispinus and brevispiiiiis, Gactauus Kruppi, 

 pileatus and latifroiis, Uiidcuchccte snpcrba and Cliintdiua noiacaiifha. 



The Ingolf-Expedition. Ill 4. 



