566 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
which he names “planktology”; the distinctions which he points out 
between the varied constituents and distribution of the plankton; and 
finally his extremely valuable suggestions for further work in the field 
which he so justly terms “a wonder-land.” 
In the translation the liberty of omitting a few personal references 
was taken, for the reason that we in this country know very little of 
the facts which have called them forth. 
In the case of several German words it has been found necessary for 
the sake of clearness to use a circumlocution. For instance, I can recall 
no English equivalent for ‘ Stoffwechsel des Meeres,” which would con- 
vey its meaning in a single word. The “cycle of matter in the sea,” 
i. e., the change of inorganic matter into vegetable and animal organic 
matter, and this finally again into inorganic matter, seemed the best 
rendering, though even this does not include all which the German term 
unplies. 
I.—HISTORICAL EXPLANATIONS. 
For the great progress made in the last half century in our knowledge 
of organic life, we are indebted—next to the theory of development—in 
a great measure to the investigation of the so-called “ pelagic animal 
world.” These wonderfulorganisms, which live and swim at the surface 
of the sea and at various depths, have long aroused the interest of sea- 
farer and naturalist, by the wealth of the manifold and strange forms, 
as well as by the astonishing number of indivi 
referred to in many old as well as in recent narratives. A considerable — 
number of these, especially of the larger and more remarkable forms, 
were described and figured in the last, or in the first half of the present, 
century. The new and comprehensive investigation of the “ pelagic 
world” began in the fifth decade of our century, and is therefore not 
yet 50 years old. 
Into this; as into so many other regions of biology, the great 
Johannes Miiller, of Berlin, equally distinguished in the realms of 
morphology and physiology, entered as a pioneer. He was the first 
who systematically and with great results carried on the “pelagic 
fishery by means of a fine net.” In the autumn of 1845, at Helgoland, 
he began his celebrated investigations upon the development of 
echinoderms, and obtained the small pelagic larve of the echinoderms, 
_and other small pelagic animals living with them, as sagitta, worm 
_ Jarve, ete., at first by “‘microscopical examination of the sea water, 
which was brought in” (1). This wearisome and thankless method was 
soon displaced by the successful use of the “fine pelagic net.” In the 
treatise ‘‘on the general plan in the dachies dar of the ad ms,” 
Norr .—Citations ae in par cutee wibieh, occur in ‘i jee leon to the list of 
publications at the end of this paper (pp. 640, 641). 
