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51
Dybder imellem 1000 og 2500 Favne. Hvad der imidlertid
ved denne Anledning er blevet kaldt "Globigerina-Ooze",
omfatter kun de Slamarter, som for en væsentlig Del
bestaar af hine Foraminiferer og altsaa har en meget høi
Kalkgehalt. Biloculinleret indeholder derimod paa mange
Steder — saaledes som de senere Analyser vil vise — kun
en ringe Mængde Kalkskaller i Forhold til sine øvrige
mineralske Bestanddele. Lerets Forraad paa Globigeriner
differerer nemlig meget i de forskjellige Dele af Nordhavet.
Biloculinerne synes derimod at være temmelig jevnt fordelte
over Havbunden, men da de i Almindelighed forekommer i
ringe Antal (sjelden ser man mere end 2 Biloculiner paa
en Kvadratcentimeter af den tørrede Bundprøve) kan de
ikke i nogen betydelig Grad bidrage til Lerets Kalkgehalt.
Paa Grund af disse Dyrs regelmæssige Forekomst og
Udbredelse i Dybvandsslammet synes det mig. at Navnet
"Biloculinler" er heldig valgt.
For at kunne gjøre os en Ide om. hvilken Betydning
hine Foraminiferer har for Dannelsen af de Afleiringer, i
hvilke de forekommer, maa vi tage deres zoologiske Forhold
i Betragtning.
Meel Hensyn til Globigerinerne er Zoologerne i
Uenighed om. hvorvidt de blot er pelagiske Dyr, eller om de
ogsaa formaar at leve paa Havbunden1. De bekjendte
britiske Naturforskere Sir Wyville Thomson. Jeffreys og Jolm
Murray er af den Mening, at Globigerinerne blot lever som
fritsvømmende Dyr i Havet, og at de først efter sin Død
synker tilbunds. Dr. Carpenter forfægter imidlertid en
anden Anskuelse, hvori ogsaa Prof. Sars er enig med liam,
nemlig at Globigerinerne i sin første Levetid er pelagiske,
men tilbringer den sidste Del af sin Tilværelse paa
Havbunden.
De øvrige i Slammet forekommende Foraminiferer
har man ikke fundet i de øvreliggende Vandlag, og de synes
derfor at være henviste til blot at leve paa Bunden. Blandt
de almindeligste af disse maa nævnes Slægten Lüuola meel
kugleründe, af Jernfosfat bruntfarvede Skaller, og Nonionina,
hvis uorganiske Del bestaar af ren kulsur Kalk. Forøvrigt
hildes der i Leret ogsaa andre Foraminiferer, der danner
sine Skaller paa væsentlig mekanisk Vis ved Sammenkitning
af Lerets forskjellige Partikler.
Levninger af kiselpantsrede Dyr er ikke synderlig
udbredte i Biloculinleret. Under Mikroskopet ser man i
de fleste Prøver enkelte smaa fine Spikuler af Svampe,
men disse forekommer clog i meget større Maalestok i
1 Med Hensyn til den zoologiske Literatur om dette Emne kan
nævnes følgende Afhandlinger: Dr. "Wallich: "The North-Atlantic
seabed." Preliminary Report by Dr. Carpenter, f From the Proceedings
of the Royal Society No. 107, 1868). "Deep-sea exploration," a
lecture by J. Crwyn- Jeffreys.
Expedition, having been met with almost everywhere in
depths ranging from 1000 to 2500 fathoms. Meanwhile,
the surface-layers to which the name of "globigerina ooze"
•has been given by British naturalists, comprises only such
deposits as consist in great part of those Foraminifera and
are accordingly distinguished by a very large proportion of
lime. Biloculina clay, on the other hand, contains in many
localities — as will appear from the results of analyses
subsequently given — very few calcareous shells compared
to its other mineral constituents. Thus, the number of
Globigerince in this clay from the different parts of the
North Atlantic varies considerably, whereas the distribution
of Biloculinæ would appear to be comparatively uniform;
but these animals occurring as a rule sparingly (more than
2 Bilocidince are seldom observed to a square centimetre
of dried deposit), they cannot of course materially
contribute to the proportion of lime in the clay. The uniformity
of occurrence characterising the distribution of these
animals throughout the deep-sea deposit of the North
Atlantic. naturally suggested "Biloculina clay" as an
appropriate name.
To fonn a just idea of the extent to which these
Foraminifera contribute to the formation of the deposits in
which they occur, we must also investigate their zoological
conditions.
With regard to Globigerince, zoologists do not agree,
some regarding those Foraminifera as strictly pelagic and
others as animals whose habitat is the bed of the sea.1
The British naturalists Sir Wyville Thomson, J. Gwyn
Jeffreys, and John Murray, are of opinion that Globigerince
during life swim freely in the waters of the ocean and when
dead sink to the bottom. Dr. Carpenter entertains a
different view, shared by Professor G. O. Sars, according to
which Globigerince are pelagic during the early stages of
their existence but pass the remainder on the sea-bed.
The other species of Foraminifera present in deep-sea
deposit have not "been met with in the upper strata of the
ocean, and would appear therefore exclusively to inhabit
the bottom. Of these animals the genera most numerously
represented are Lituola, with globular shells, brown in
colour from the phosphate of iron they Contain, and Nonionina,
of which the inorganic part consists of pure carbonate of
lime. For the rest, North-Atlantic deposit contains divers
other Foraminifera, which build up their shells in greater
part mechanically, by cementing together minute particles
of the clay.
Siliceous remains of animals are not particularly
abundant in Biloculina clay. Examined under the microscope,
most of the samples were found to contain delicate spicules
of sponges, but such constituents occur in far greater num-
1 The following are some of the chief works in which this
subject is treated: — Dr. Wallich: "The North-Atlantic Sea-Beil:"
"Preliminary Report by Dr. Carpenter (From the Proceedings of the
Royal Society, No. 107, ls(i8). "Deep-sea Exploration," a Lecture by
J. Gwyn Jeffreys.
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