174 



DEPARTMENT OF THE NAVAL SERVICE 



Vineyard. The last two localities are within a day's journey of Woods Hole, Plymouth 

 harbour being- a boreal locality, whilst the Gulf Stream carries a tropical and subtro- 

 pical fauna. As the four localities covered by Wheeler are typical of their respective 

 districts, it may be desirable to tabulate his records for facility of reference and com- 

 parison. These records relate primarily to the fauna at or near the surface, a fact 

 which may partly account for the absence of such representative boreal species as 

 Calanus hyperboreus, Euchaeta norvegica, and Metridia longa, which frequent the 

 deeper strata, of water around 40 or 50 metres, although they sometimes ascend into the 

 surface layers. They are essentially open-water forms, and it is probable that Ply- 

 mouth harbour and Vineyard sound are too close to the land for them to find the 

 necessary conditions. 



Table A.— Wheeler's Records (July 1899). 



X means present. 



XX means abundant. 



Of the two divisions of the free-living Copepods, namely Gymnoplea or Calanoids 

 and Podoplea or Harpacticoids, the former is more directly concerned with the purpose 

 of the present investigation. Of all the species which have passed under review, the 

 one that is most widely distributed and most abundant in the fishery districts is Cala- 

 nus finmarcMcus, known to the more observant fishermen as " red feed " or " herring 

 feed ". It is part of our problem to deal with this and some other species, not only 

 in the full-grown condition but in such of the stages of early growth as are brought 

 up in the tow-net. Six stages in the postlarval development of C. finmarchicus have 

 been specified by Professor Gran (1902) who seems to have been the first to attempt 

 an analysis and interpretation of the mode of occurrence of this species in the Norwe- 

 gian North Sea, where its superabundance had been previously signalized by G. O. 

 Sars. Gran's six stages, adopted with slight inversion by Damas (1905), may be re- 

 garded as typical for the Calanoids as a whole, although in some cases the procedure 

 differs remarkably as regards the details of subdivision and fusion of the abdominal 

 segments Thus, at a certain stage, the young Met'^idia has a four-jointed urosome 

 (hind-body) in either sex; the adult female has a three-jointed urosome through fu- 

 sion of the first a?id second segments; the adult male has a five- jointed urosome through 



