602 REPORT OF COMMISSIONER OF FISII AND FISHERIEB. 



yellowish or reddish "animal uiiish/' composed in by far the greater 

 part of copepods. In the journal which I kept in the winter of 1S0G-G7, 

 at Lanzarote, in the Canary Islands, of the varying constitution of the 

 plankton, for many days there is only the remark : " almost pure buck- 

 ets of copepods," or " the collection consisted almost entirely of Crus- 

 tacea, by far the greater part of copei)ods." That these small crus- 

 taceans form the chief food suj^ply for many of the most important 

 food-fishes {e. g., the herring) has long been known. In the Arctic as well 

 as the Antarctic Ocean Calanus finniarcMvus and a few related species 

 form in general the chief bulk of the plankton, and furnish food for 

 pteropods and cephalopods, for the divers and penguins, for many fishes 

 and whales. On the voyage from Japan to Honolulu the ChaUemjer 

 sailed through wide stretches of the :N"orth Pacific Ocean which were 

 covered with red and white patches, caused by great accumulations of 

 two species of small copepods, the red being Calanus propinquus (8, p. 

 758). In many other regions, from the Polar Circle to the Equator, the 

 ship passed through white bauds many miles wide, composed solely 

 of copepods (8, p. 843). That their appearance is very irregular and 

 dependent on many conditions is true of this very important group 

 of plankton animals as for all others. For two days the Challenger went 

 through thick shoals of Corycaeus pellucidus. For the next three days 

 the copepods had entirely disappeared. 



Hensen has made statistical statements upon the appearance of the 

 copepods of the Xorth and Baltic seas (9, p. 45). Chun has lately showu 

 that this order plays a highly significant role, not only at the surface, 

 but also at considerable depth? (000 to 1,300 meters), (15, p. 25). " Their 

 abundance and richness in forms in greater depths is absolutely aston- 

 ishing. Larval forms of species sessile or living upon the bottom min- 

 gle in confusion with the young forms and sexually mature stages of 

 enpelagic species. Many species hitherto regarded as varieties are 

 numerously represented in the depths." On the other hand, the order 

 seems to be very poorly represented at very great depths. The Chal- 

 lenger found only one very characteristic deep-sea species in 2,200 

 H'diliom^—PontostratioUles ahyssicolla .{S, p. 845). Some genera never 

 leave the surface and are autopelagic, e.g., Pontellina (15, p. 27). 



Ostr acod a. —ThQ ostracods are, next to the copepods, the most impor- 

 tant Crustacea of the plankton, and are represented at the surface as 

 well as in ditterent depths by masses of many species. In the (ecology 

 of the ocean they play a similar role, as do the near-related cladocerans 

 {I)aj)hni(hv) in the fresh water. The Challenger collected 221 species of 

 ostracods. Of these 52 were found below 500 fathoms, 19 below 1,5(>0, 

 and 8 below 2,000 fathoms in depth. Many ostracods, like many cope- 

 pods and other crustaceans, belong to the most important luminous 

 animals of the ocean. On my journey to Ceylon (in the beginning of 

 November, 1881), as well as on the return trip (middle of March, 1882), 

 I admired as never l)ef()re the oceanic light in its splendor. "The whole 

 ocean, so far as the eye could reach, was a continuous shimmering sea 



