602 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
yellowish or reddish “animal mush,” composed in by far the greater 
part of copepods. Inthe journal which I kept in the winter of 1866-67, 
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 copepods.” That these small crus- 
taceans form the chief food supply for many of the most important 
food-fishes (¢. g., the herring) has long been known. In the Arctic as well 
as the Antarctic Ocean Calanus finmarchicus 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 Challenger 
sailed through wide stretches of the North 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 bands 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 North and Baltie seas (9, p. 45). Chun has lately shown 
that this order plays a highly significant réle, not only at the surface, 
but also at considerable depths (600 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 
eupelagic 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 
fathoms—Pontostratioides abyssicolla (8, p. 845). Some genera never 
leave the surface and are autopelagiec, e.g., Pontellina (15, p. 27). 
Ostracoda.—The ostracods are, next to the copepods, the most impor- 
tant Crustacea of the plankton, and are represented at the surface as 
well as in different depths by masses of many species. In the cecology 
of the ocean they play a similar role, as do the near-related cladocerans 
(Daphnide) in the fresh water. The Challenger collected 221 species of 
ostracods. Of these 52 were found below 500 fathoms, 19 below 1,500, 
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), 
IT admired as never before the oceanic light inits splendor. ‘The whole 
ocean, so far as the eye could reach, was a continuous shimmering sea 
