Encyclopaedia Britannica > Volume 21, ROT-Siam

148
S A G —S A G
Tartary, which was discovered a few years later .by a, Japanese,
Mamia Rinso, whose discovery is embodied in Siebold’s Nippon.
The Russian navigator Nevelskoi, in 1849, .definitively established
the existence and navigability of this strait; since that time the
Russian expeditions of Boshnyak (1851) and Rimskiy - Korsakott
(1853) continued the explorations, and in the latter year a Russian
post was temporarily established at Aniva Bay. L. Schrenck in
1855-56, and MM. Schmidt, Glehn, Brylkin, and Shebumn m
1860, explored the geology, fauna, flora, and ethnology of the island ;
M Lopatin in 1867 explored, on foot, the east coast; MM. Dobrot-
vo'rsky published (1869 and onwards) interesting data as to the
inhabitants, and M. Polyakoff was entrusted in 1881-82 with a
detailed exploration, and returned with rich ethnological and zoo¬
logical collections, with regard to which only preliminary reports
have as yet been published. (P. A. K.)
SAGINAW, a city of the United States, capital of
Saginaw county, Michigan, lies on an elevated plateau
about 30 feet above the water on the left bank of the
Saginaw river, which falls into Saginaw Bay on Lake
Huron, about 18 miles lower down. It is a railway junc¬
tion of some importance, 100 miles north-west of Detroit,
is connected with East Saginaw by a street railway, and
can be reached by the largest vessels that ply on the lake.
The upper branches of the river are also available for boat
traffic throughout a considerable district. Saw-mills,
planing-mills, and salt-works are the principal industrial
establishments. The population was 7460 in 1870 and
10,525 in 1880. The city charter dates from 1859, the
first settlement from 1822.
SAGITTA. The name “ Sagitta ” was given by Martin
Slabber in 1775 to a small marine worm which is now
known as the type of a distinct group, the Chxtognatha
(Leuckart). The group comprises two genera {Sagitta
and Spadella) and a considerable number of species; they
are small transparent pelagic animals, varying in length
from a few lines up to two inches, and are universally dis¬
tributed. The body (see fig.) is elongated and furnished
with a tail and lateral fins, which are prolongations of the
chitinous cuticle; the head is provided with a great number
of variously shaped chitinous setae. The body is divided
by transverse septa into three distinct segments : the first
septum is placed just behind the head {st), the second {st)
about the middle of the body, separating the ovaries and
testes. The body-cavity is likewise separated into right
and left halves by a continuous vertical mesentery, which
suspends the gut. The alimentary canal is a simple
straight tube of uniform structure passing from the mouth
to the anus, which is placed ventrally and at the second
•transverse septum ; the alimentary tube is ciliated and is
unprovided with glands of any kind. The body-wall is
composed of (1) an outer layer of epidermis, which secretes
the chitinous cuticle already referred to,—the thickness of
the epidermis varying from five or six cells in the region of
the head to a single layer of cells in the “ fins (2) a deli¬
cate structureless supporting lamella; (3) a layer of longi¬
tudinal muscles. These last have a peculiar arrangement
and structure : they are disposed in four bands, two dorsal
and two ventral, the action of which is evidently favour¬
able to producing the onward movements of the creature.
The muscular fibres, which are transversely striated, are
arranged in a series of lamellae whose direction is per¬
pendicular to the longitudinal axis of the body. Projec¬
tions inward of the supporting lamella bear on either side
a single row of muscular fibres ; a similar muscular struc¬
ture occurs in the Nernaioidea and in many Oligochseta.
In the anterior region of the body the muscular layer is
differentiated into special muscles for the movement of the
setae. (4) The body-cavity is lined by a delicate peritoneal
epithelium closely applied to the muscular layer of the
body-wall and to the gut. The nervous system consists
of a cerebral ganglion and a large ventral ganglion—the
two united by commissures which pass round the gut;
both ganglia are embedded in the epidermis. This primi¬
tive condition of the nervous system is retained in other
lowly organized worms (e.y., Poly-
gordius). The ventral ganglion is
connected with an intra-epidermic
nervous plexus which surrounds the
whole body. Eyes are present, be¬
sides a number of tactile cells upon
the outer surface of the body; an¬
teriorly is a ring-shaped structure
(r) which is supposed to be olfac¬
tory in function. The generative
organs consist of ovaries and testes,
which are united in the same indi¬
vidual ; the ovaries (e), placed an¬
terior to the testes, are furnished
with oviducts, which appear to ter¬
minate in a csecal extremity. The
testes (/io) are placed behind the
second septum; they are each fur¬
nished with a vas deferens opening
on to the exterior and into the
body-cavity by a ciliated funnel.
For embryology, see Balfour, Com¬
parative Embryology, vol. i. p. 303.
In spite of the detailed knowledge
which we now possess of the structure
and development of the Chsetognatha, the
systematic position of the group remains
a matter of the greatest uncertainty. That
they are an archaic group is shown by
their hermaphroditism, by the primitive
condition of the nervous system, and by
the persistence of the vertical mesentery
among other characters; in all these
points and in others they agree with such
primitive Annelida as Protodrilus and
PolygordAus. On the other hand, their
similarity to the Nematoidea has been
dwelt upon; the disposition of the muscles
is the same in both groups, and the Gor-
diacese have the gut suspended by a dorsal
and ventral mesentery in the same fashion
as has been described above in Sagitta;
Spadella cephaloptera
(Busch).
the Cheetognatha differ, however, from the Si, septa dividing body-cay ity
Nematoidea in the important fact of their
segmentation. On the whole, it appears
that the Chxtognatha are best regarded as
a special phylum equivalent to such groups
as Annelida, Platyhelminthes, Nematoidea,
hut having no special relation to any one
of them.
transversely; <72, cerebral
ganglia ; ii1, commissure
uniting this with ventral
ganglion (not shown in
fig.) ; nerve uniting
cerebral ganglia with small
ganglia on head ; nr, ol¬
factory nerve ; d, aliment¬
ary canal; r, olfactory
organ ; te, tentacle; f, tac¬
tile hairs springing from
surface of body ; e, ovary;
el, oviduct; ho, testes ; sg,
vas deferens ; /2, f3, lateral
and caudal fins; sh, seminal
pouch. The eyes are indi¬
cated as black dots behind
the cerebral ganglia.
SAGO is a food-starch prepared
from a deposit in the trunk of several
palms, the principal source being
the sago palm, Metroxylon Rumphii
(Mart.), and M. hrve (Mart.). These
palms are natives of the East Indian
Archipelago, the sago forests being especially extensive in
the island of Ceram. The trees flourish only in low marshy
situations, seldom attaining a height of thirty feet, with a
thick-set trunk. They attain maturity as starch-yielding
plants at the age of about fifteen years, when the stem is
gorged with an enormous mass of spongy medullary matter,
around which is an outer rind consisting of a hard dense
woody wall about two inches thick. When the fruit is
allowed to form and ripen, the whole of this starchy core
disappears, leaving the stem a mere hollow shell; and the
tree immediately after ripening its fruit dies. When ripe
the palms are cut down, the stems divided into sections
and split up, and the starchy pith extracted and grated to
a powder. The powder is then kneaded with water over
a strainer, through which the starch passes, leaving the
woody fibre behind. The starch settles in the bottom of
a trough, in which it is floated, and after one or two
washings is fit for use by the natives for their cakes and