'^j^ p :5^

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THE

JOURNAL

OF TUK

COLLEGE OE RCIENCE,

IMPERIAL UNIVERSITY,

jAi^A^r.

VOL. V.

'îff H ;/< ^ I'll If
PUBLISHED BY T1I1<^. UXIVERSTTY.

TOKYO, JAPAN.

1893.

MEIJI XXVI.

2q 'X 5

CONTENTS.

Studies on Reproductive Elements. I- Spennatogonesis, Ovogenesis, and
Fertilization in T>ii(j)toiin(.s sp. ]!v C. Iskhcawa, I'h. 7\, Itiiifil.iihdJnislii,
Professor of Zoology, Agricultural College, Imperial Uiiiversity. O^ilh
I'lateT.) I

Further Studies on the Formation of the Germinal Layers in Clielonia.

(Contributions to tlie Embryology of lîeptilia III). J>y K. MiTsrivVia,
rii. ]>., lUijaliihakushi, Professor of Zoology, College of Science, Imperial
University, Tokyo, Japan. ("Willi I'lntcs If-f\'.j 3;!>

On the Development of Limulus Longispina. i5v Kamakichi Kishinouvk,

I!i(/(i/.-uvhi, College of Science, Imperial Cniversity. (With I'latcx V-Xf.) 5i}

On the Lateral Eyes of the Spider. I>v Kamakkhi Kishinouyk, JH'jakushi,

College of Science, Imperial University 101

Notes on a Collection of Birds from Tsushima. ^>v I. Ihma, I'h. l>.,

I!iij<il:iislu\ lliiiii/,ii]t(iJ,-iis/u\ Professor of Zoology, College of Science, Im-
perial University. ("With I'laU-s XII.) 105

On the Formation of the Germinal Layers in Petromyzon. P>v S.

Hatta. Zoological Laboratoi-y, College of Scit'nce. ("With I'lotes Xfff.
XIV.) Vl\)

The Disturbance of Isomagnetics attending the Mino-Owari Earth-
quake of 1891. 1''^' A. ÏANAKAnATK, I liijahuh'/hiishi. /•'. //. V. /■,'., I'ro-
fessor of Physics and H. Xac^aoka. lliiioLiishi. Assist. Professor of I'liysics.
College of Science, Imperial University. rWitli I'lalts XV-XX[f.j ... llff

Optical Note. K. Takizaw\ lOH

The Archaean Formation of the Abukuma Plateau. P>v P. Koiv,. rii. i>..

l!i[iii/.-iihiil,'iishi, Professor of Genlogy, College of Science, Imperial Univer-
sity. rWith riutes XXlI-XXVlf.) 197

On the Cause of the Great Earthquake in Central Japan, 1891. I'>v

P. KoTc), I'h. IK, IHii'i/ntJtn/riishi. Professor of Geology, College of Science,
Imperial University. (With I'hitrs XXVfff-XXXW) '19r>

studies of Reproductive Elements.

I. Spermatogenesis, Ovogenesis, and Fertilization
in Diaptoimis sp.

By

C. Ishikawa, Ph. D., Rieakuhakushi.

Professor of Zoology, Agricultural College, Imperial University.

With PL I.

A. DESCMIIITTVE PART.

The species of Diaptomn^ on wliicli llie fbllinving olj.'ervationa
were made is very abundantly found in an old pond in tlie University
oTonnds. Its breeding- orr-urs repeatedly at an interval of about
two uK^ntlis during tlie colder half of tlie year.

1. Testicular Sac.

])V pxaniining the testis under a microscope, we are struck widi
the varietv of celluhu- elements found in it. Near to its two ends we
tind cells in active division, while its median part is filled with cells
whose nuclei a.re in the resting stage. We can therefore divide the
entire sac into different zones just as has been done hy Ed. van Bmcdeii
and Jidiny^ and lately by 0. Heiitvig,^''^ with the testis of Ascaris
megalocepliaJa. Following tlie example of these luithors we shall
speak of the ])lind end as the formative zone, the middle part as tlie
growiuff zone, and the part near the vas-deferens as the zone of ripening.

In the formative zone, the nuclei are toleralily large, and with

2 0. ISHTKAWA.

verv little prc^topl-.i.^m. The chromatic elements are very much
elongated and appear as so many minute rods. Many of the cells are
in the state of division.

In the growing zone (" Wachstlmmszone") the nuclei recede to
the state of rest, and the germ-cells grow to nearly double their size
after division in the first zone. 'I'his stage is, however, not so well
marked in this animal as in Ascaris ; we can nevertheless distinguish
it pretty easily by the absence in it of karyokinetic figures.

And in the last zone we find again the active multiplicatit^n of
the cells. "Jede Zelle zerfallt jetzt durch zwei Theilungen, die sich
unmittelbar aneinander anschliessen, iri 4 Elemente, welche sich direct
zu den befruchtenden Samenkörpern umbilden. "^^^^

Fig. 1. represents a longitudinal section of a testicular sac not
very highly magnified, tlie lower end of the figure showing the blind
posterior end and the upper end the place wliere the vas deferens takes
its origin. The tln-ee zones here enumerated can be clearly seen
even bv this figure. The entire lower third of the sac represents the
formative zone in which are seen a few cells in division. The next
zone is well characterized by the peculiar appearance of the chromatic
elements and occupies the iniddle portic^n of the sac, while the last zone
or tlie zone of ripening is seen at the anterior end, well characterized
by the presence of many karyokinetic figures in it.

a. The Formative Zone. — This zone occupies nearly one-third of
the entire testicular sac near its posterior end. The cells in this
part are found partly in the state of division and partly in the state
of the so-called " skein " stage (Kniiuelstadium), showing thus very
clearly that these are in active multiplication, as stated above
(fig. 1 k fig. 2). The chromatic elements of the nuclei in the
"skein" stage are found to be of \ery different thicknesses, owing
to tlie dilferent stages in which we observe them ; and their number

STUDIES OF REPRODUCTIVE ELEMENTS: I. 3

ronld not be exactly made out, except in tlie srages just before
and during the division. At this stage each chromatic; element
assumes at first a rod-like shape, and then becomes constricted in its
median portion, transversely to its long axis, thus resemblino- in
shape a dumb-bell (fig. 2, left end). These dumb-bell shaped bodies
are eight in number, and arrange themselves in form of a rino- on
whose periphery they lie. This is the stage of the spindle. Tt will
be noted that the s})indle appears different to the eye according to
the methods «jf preservation we use. Thus preparations treated with
hot-alcoholic sul^limate (30 % alcohol to which a few drops of con-
centrated sublimate solution have l^eeii added) show no achromatic
fibres connected witli the chromatic elements, while those cells which
are killed with aceto-picric-acid exhibit them verv distinctly. The
central Ijodies can also be clearly made out witli Grenadier's haema-
toxylin. Jn the process of division each dumb-bell shaped chromo-
some elongates and becomes divided in its middle part, so that one
luilf of the d(unb-bell goes to one pole and tlie other half to the other.
The two (laugliter cells arising ])y division of a mother cell contain
each eight single chrom(js()mes, each of which is half one of the
original cliromosomes. The only différence from tlieordinarv karyo-
kinesis consists in the mode of division of the chromosomes, which
generally divide longitudinally and not transversely.

Fig. 2 represents more highly magnified the extreme posterior
end of the testis shown in fig. 1. AVe now see a number of primi-
tive sperm-cells with very large nuclei, the chromatic elements of
which appear as so many minute rods. At the left hand corner is
seen one of the cells in division, in wliich five dumb-bell-shaped chromo-
somes are represented in a single row at the equator of the spindle ;
the other three, not here visible because lying at a lower level, could
be made out by focussing the microscope. At the i-ight hand 1 ha\e

4 C. ISHIKAWA.

drawn from the testis of another inclividual, a cell found in tliis region
Avhich represents a further stage of division, in which the chromatic
elements are already separated from each other and lie near the poles
of the spindle. I will call these primitive cells by the name oî primary
spermatic cells ("Ursamenzellen" of German authors). They generally
divide two or three times, and thus fAve rise to the cells of the o'r(3wino'
zone which will be ; poken of as sperm-mollicr -cells ("Samenmutterzellen"
of German authors).

h. Tlie Groioinii Zone. — The cells at the beoinnin<>' (^f this zone
are relati\'e]y small and the eight chromosomes begin gradually to
elongate and at the same time the nuclear membrane becomes distinct.
Hand in hand with this change the cell-body enlarges, while the
nucleus appears to get snndler and more conipr.ct, colouring very
deeply with reagents, and at last Ijecomes quite homogeneous, owing
to the thick consolidation of the chromosomes. These stages are seen
in tigs, o, 4, and 5. In fig. 3 the chromatic elements are just begin-
ning to elongate, have continued to change in cells represented by
fig. 4, and lastly in fig. 5 ha^e become quite homogeneous.

The next chano-e in the cells is the dissolution aji-ain of the
elements (figs. 6 and 7, the former rejH'esenting the polar view and
the latter that from the side). Instead of a homogeneous mass we now
see a number of elon^'atcd chromosomes irrei>'ularlv Ivino- in the
centre of a cell, Ijut generally more or less gathered to one side
remindinsf one reinarkabJv oï the fi^-ures i^iven by Hertwin in the
same stages of development in the spermatic cells of Ascaris mcijalo-
ccphala. Tlie only différence between them and our figures consists
in the absence of a nuclear membrane in the latter. The chromosomes
become shorter and thicker and assume at last a short rod-like shape
just as we find them in primary speruuitic cells preparing to divide.
Fig. 8 represents these changes. At the left hand of the figiu'e is

STUDIES OF REPRODUCTIVE ELEMENTS: I. 0

seen a ceJl whose chronititic elements are somewhat sliorter tliaii
those represented in tig. 6, and one at the right shows distinctly eight
short chromatic rods.

The sperm motlier-cells increase all the while in size u]) to tin;
stage which we have called the zone of ripening ("lieifezone"), and
which we will now proceed to descrihe.

c. The Zone of Eipening. — The eight chromatic rods now begin to
be c()]i:>trictcd at their middle point giving rise to eight dumb-bell-
shaped Ijodics as Ijefbre. Tliese arrange themsehes in the shape
of a ring a]id each ol them Ijecomes divided into halves on tlie appear-
ance of achromatic fibres as before (tig.-. 1), 10, and 11). In tig. i)
which is drawn from a specimen killed with liot picro-acetic solution,
the ei'dit chromatic elements are beiiinnini'' to di^'ide transversely,
while in the cells represented by tigs. 10 and 11 (treated with acetic
acid solution of methylgreen) the division has proceeded a little farther.
The large size of the cells represented l)y these tigures is due perhaps
to the pressure exerted upon them 1)y the cover-glass. The cells
resulting from this disi.-ion contain therefore each eight single chrijmcj-
somes, which noNv [)rcpare to divide dircdhj witJtuiU an inter vcniiuj
resting stage. The eight siugle chr(jmosomes in each of llie cells
after the division, arrange themselves in (jne plane, and mostly at the
periphery of a ring as usual, but somet:imes one or two chromosomes
can be foimd in the interior of the ring. These cells now begin to
be divided into two on the appearance of the attractive sphere, central
bodies, etc., as usual in the karyokinetic cell division, but with this
important difference concerning the chromosomes, that eaeh eiiiomosonte
does not heeoine divided into tn-o as usual, hut remains undivided during
the division, so that four of (he eight go hodiig into one cell and tlie
other four into the other.

Figs. 12, 13, 14, 15, :!iid 1() represent i hese changes. In lig. 1:^,

6 C. ISHIKAWA.

which is drawn from a specimen treated with acetic acid sokition of
methylgreen, and shows the eight single chromosomes in the e(|ua-
torial zone of a spindle, five of tliese are seen on one side while the
other three lie on the other side. The cell body appears to he larger
than those represented by figs 13. 14, and 15, which are taken fr(jm a
specimen treated with picro-acetic acid solution. This difference in
size is due partly to the pressure of the cover glass, but chiefly to
the action of the acetic acid. Fig. 13 shows the polar view of a
spindle at the stage of fig. 12. Of the eight chromosomes, seven lie
at the periphery and one in the middle of a circle. In fig. 14 a
.similar spindle seen irom the side is represented, while tig. 15 shows
the cell-divsion nearly completed, four chromatic elements being drawn
to one pole and foiu- to the (jther pole. The cell-body is also nearly
at the end-stage of its division. A similar stage is represented more
clearly by fig. 16.

Tlie nucleus of a cell after this di\ision again acquires a
membrane and the cbromosomes become also indistinguishable, colour-
ing \ery deeph' and unilbrmly. At a place a little farther outward
the nucleus ao-ain becomes uneven to the staininii- and shows more
or less distinctly indications oï chromosomes coming t(j occu])y posi-
tions at the periphery of the luicleus Avhose central part now shows
a clear space. In this condition the sperm cells again begin to
grow gradually, and the chromosomes come again to be seen more or
less distinctly as \evy fine threads and lying rather irregularly in the
nucleus. In this growth of the cell, the nucleus progresses more than
the cell bod}^, so that the latter becomes proportionally much reduced,
and when the cell passes into the vas deferens no trace of the cell-body
can be detected. The nucleus now assumes the characteristic elongated
sha|)e we find in the s])erm cells contained in the spermatophore sac
attached near the female opening. Illustratifjns of these changes are

STUDIES OF REPRODUCTIVE ELEMENTS: I. 7

seen in %s. K), 17, 18, 19, 20, 21, and 22, whicli are drawn from a
testis and vas deferens of one and tlie same indi\idi];d nnder tlie same
magnifying power.

2. The Ovarian Sac.

Tlio ovarv of Diaptoinui^ I examined, consisted of a median
unpaired part — the ovarv ])i-oper — and tlie o\idiicts ai-ising on
both sides of it. For the sake of eonvenience I haxe divided the
contents of the ovary into three different zones as in the case of t1ie
testicular sac, although the distinctions are here not so complete -as in
the latter : a) the formative zone which occupies the extreme blind end
of the sac ; /)) tlie (iroioinfj zone tilling the rest of the whole ovarian sac
and part of the oviducts ; and <•) tlie zone of ripening occupying the
oviducts alone. In fict the ])rocess of ripening <h)es not end within
the l)ody of the animal : the second polar body, as was first observed
by Gi'ohhen,^^' is foi-ined after tlie eggs have been laid in the breeding-
sac and attached to the base of the tail of a female. The ripening zone
moivoxer overhips the hinder part of the second zone.

a. The Formative Zone. — At the extreme blind end of the ovarian
sac, which ends in a very narrow tube C(^ntaining but a single row of
germ-cells, we meet with cells quite similar to tliose we find in tlie
posterioi- third of a testis. A comparison of figs. 23 and 24 with fig. 2
of the testis will at once show this .-huilarity. In these cells of the
tjvarian sac, too, a relatively large nucleus contains chromatic nets whicli
are certainly in the '' skein " stage, but the karvokinetic figures are \er\-
scantily to be seen. Xext follow the cells which to all a])pearance
seem to corres])oiid with the testicidar cells as represented in fig. o
and whi(h are ;ippareiitl\' in the beginning of a J/,s77//V')/i .s^a^e. The
chromatic fibres Ix'come finei" and finei- till thev appear as minute dots

M C. ISHIKAWA.

in tlio rniolen^^ ; ;it the same time a mideolns appears within the
nucleus and the egg o-ets int<> the next or the growing zone.

h. The Growing Zone. — Strictly speaking this zone hegins from
the point where the germ-cells get into the dispirem stage. The
nuclear threads wliich now appear as minute dots hecome gradually
fainter till at last they disappear completely from the view. The
o-erminal vesicle too-ether with the eo-g'-cell o^rows larger and lar^'er,
and the germinal spot which always remains single also enlarges.
As has heen already stated l)y Vaut Mcujcr oî Eupagurus,^^^^ and after
him hy myself of Ati/ep]i,ira^^^'^^ the growth of the germinal vesicle is
relatively less than that of the cell-body.

Thus the ovary or germ-gland (" Fveim<lruse '" of C/r/n.s) can also
he divided into two ]iarts in accordance witli the descripti(~)n given hy
Haech'v of Cyclops. ^'^^ Just as in that case, the blind eiid is characterized,
as a!)ove said, bv the presence of a numljer of nuclei in division. Tin's
is the "erste Phase der Ovogenese " of iîaé!t'^'t'r and my formative
zone. It is f )l]owed by tlie second part, the growing zone, wliich
extends from here to the distal end of the oviducts. Here are
passed two important stages of ovogenesis, the first o{ which is
characterized by the appeara.nce of a nucleolus witln'n the nucleus and
the disappearance of the chromosomes, and the second by the formation
of the yolk-graiudes, and along with tin's the rapid enlargement of the
germinal cells. It will perhaps be better to recognise in this zone two
parts according to the stages of development of germ cells, as is d(Uie
by Haecker, who takes as the first ])art that portion of a germ glarid
where the nuclear membrane appears and the contiMu* (^f the nuclear
thread becomes indistinct, and " zuo-leich findet sich ein Xucleolus
vor, der Hand in Hand mit der A^erwischung der Schleifenin-
dividualität an Grösse zunimmt. jSTeljen diesem grossen Xucleolus
zeigen sich schon in sehr jungen Keimzellcü regelmässig ein oder

STUDIES OF REPRODUCTIVE ELEMENTS : I. »

zwei runde Körper, die ich vorläuHg al« Micronucleolen bezeichnen
möchte." This, as will be seen from my ligures, corresponds exactly
with what I have seen in the egg-cells of Diapfomus, the sole differ-
ence lying in the absence of the small bodies besides the nucleolus
which he calls micronucleoli. These appear, in my case, first in eggs
that are nearly ripe, and shortly before tlie formation of the first
polar body, as will be seen later on.

In fig. 24, which represents a part of an ovarian sac, are seen
on the right the cells of the formative zone, which towards the left
gradually pass over into those of the growing zone. The chromatic
elements, as will l^e seen, disappear as we pass from the jjlind end
outward, while a distinct nucleolus comes into view.

The formation of yolk-granules and consequently the rapid
development of germ -cells takes place first when the eggs get into
the oviduct, just as in the case of Gijclops. As in that case also, all the
eo-(y-cells in the oviduct are at a oiven time in one and the same stage
of development. Hacchcr says on this point : " die sammtlichen
Eizellen des nämlichen Individuums" are found " stets auf fast voll-
kommenen gleicher Entwicklungsstufe."

Of the origin of volk ui'aniiles I liaNc not much to sav. Thev
originate, as [ stated of the e^^^^^ of Atye'plilra, in the body of the egg-
cell ijear the periphery rather than near the centre.

The next change in the development of the egg- cells is the a [)-
pearance of a number of small bodies in the nucleus, besides the nu-
cleolus, which correspond with the " Micronucleolen " of Haecker ;
tliere appear at the same time a number of dumb-bell shaped chro-
mosomes exactly corresponding with those found in the spermatic
cells. The iiucleolus at this time is found to l)e much reduced in size
and it shows very often a number of vacuoles of variable sizes. Like
HaecliiV I am also ;i1 a loss to know wlu'tlicr tlie iiiio-oniilcoJi arise

3 0 C. ISHIKAWA.

from tlie nucleoluis or independently in the nuclear plasma. At all
events the nncleolas here hi in stages of regressive metamorphosis, and
in many cells in these stages no trace of it can be seen within the nu-
cleus. As with the similar developmeritnl stages of spermatic cells,
I will call the stage after this the zone of rq)eiii7iij.

Fiof. 25 shows two neio-hbourinsf eofo-s of an animal in which the

O o o Co

eight dumb-l)e]l shaped chromatic elements have appeared. The
u'crmiiial vesicle has now attained its Isu'o'est size. In one of them, on
the left liand side of the figure, we see besides the eight chromatic
elements a germiijal spot, (now greatly reduced in size), and nine small
round vesicular bodies which certaiidy correspond to the micronucleoli
of Haeclicr. In tlie germinal vesicle of the other egg, the germinal spot
is no more to be seen. This figure is compounded from three suc-
cessive sections, in such a manrjer that from the first and second
sections the eo-o^ on the left side is drawn, while from the second and

Co '

third sections that on the riodit side is drawn.

o

c. The Zone of Bipeninfj. — As îdready stated, there is no distinc-
tion between the eggs in the last zone and those in the zoiie of
rii)eniii"', and tlie eii'u'S u'o throuji'h, in one and the same zone, the
changes mentioned under the headinii" of the u'rowinii' zone and the
changes tliat are now to l)e mentioned ; so tliat these two zones are
not distinct in the o^arian sac, as they are in the testicular sac. The
onlv reason for counting them separate consists in the advantage ol)tain-
ed when we come to conijiare these two kinds of germ cells together.

The esrs" cells, as mentioned above, now show distinct chromatic

CC ' '

elements each in the shape of a dumb-bell. These are eight in number
and are scattered about without any order in the nucleus. Shortly
after the appearance of the chromatic elements the micronucleoli as
well as the nucleolus disappear, and the nudear mendjrane becomes
also indistinct and finally disappetu's.

STUDIES OF REPEODUOTIVE ELEMENTS: I. 11

The eight chromgsoiiies now arrange themselves on the periphery
of a circle just a.s in tlie case of spermatic cells. The attractive sphere
and the central bodies are not, as in the testicular cells, to he observed
in preparations treated with sublimate-alcohol, but are very dis-
tinct in the cells killed with picro-acetic acid. Figs. 26-29 give the
eggs in these stages. Fig. 26 represents only the small part of an egg,
in which the spindle lies. The nuclear membrane has already dis-
appeared, and no trace of the germinal spot and the micronucleoli is to
be seen. Five of the dumb-bell- shaped chromosomes are seen in a
curved row from this side, and the three others can be seen, bv focussino-
the microscope, below these. In fig. 27 we have a polar view of such a
spindle, while fig. 28 givea another spindle as seen from the side. These
three figures are drawn from preparations treated with hot sul)limate
alcohol, and no trace of achromatic fibres is to be seen. Fig. 29 gives
the spindle in the same stage -as that of figs. 26, 27, and 28, but treated
with picro-acetic acid. Here we see not only the achromatic filn'es,
Init also a trace of the vesicular membrane quite distinctly.

This spindle is tliat of the first polar body, and travels gradually
towards the surface of the eo-o- where each chromosome be^'ins to
divide transversely just as in the first divisi(^n of testicular cells in the
zone of ripening. This di\'ision gives rise to the first polar body, whicli
is thrown out of the egg, while this is still in the oviduct. There are
thus eight cliroinosoincs in the first 'polar hodij and the same nuniher in
the other lialf of the germinal vesicle wliicli remains ifi the egg. Tlie latter
begins to divide directly, but now in such a manner that four of the
eight chromosomes are separated of from the other four. This is the form-
ation of the second polar body, which thus exactly corresponds with the
last division of the spermatic cells, as has ])een shown by Plafner'-^^^ in
Aulacostoma and liv Hertu-ir/^'-^ in Ascaris ea'S's. These stao-es are re-
presented ])y figs. 30-35. In fig. 30 the spindle of the second polar body

1 2 C. ISHIKAWA.

is seen from the pole. The eight single chromosomes are clenrlv t(^ l)e
seen lying in the equatorial plane of the spindle. The first yxihv hodv
is no more to be seen. Figs. 31, 32, and 33 show the spindle in more
advanced stages. In the first two figures the chromatic elements
are still very short, but in the last (fig. 33) thev are rather elongated.
Figs. 34 and 35 show the stage where the second polar bodA^ has en-
tirely separated from the egg nucleus, whicli latter has now accpiired a
vesicular f^rm. The four chromatic elements are more or less distinct-
ly to be seen in tlie second polar body.

At the stage between the expulsion of the first a.nd the second pohu*
bodies the egg passes out of the oviduct int(^ the breeding sac, so that
the first polar body lies outside the egg-membrane, which is formed
after its expulsion, and after the penetration of a spermatic cell into
the egg, which takes place at the extreme distal end of the oviduct.
That in Cnpepoda the first polar body lies outside the egg-membrane
and therefore is not to be found in eggs that have come out of the
oviduct was first shown by Grohheii'^^ in CetocJiilus and afterwards by
31. Niisshaumf^'''^ in many Cirripedce, in which it had been foreseen by
Weisniann.

3. A Comparison of the Rqiening Phenomena
in Eijij- and Sperm-cells.

As is shown in preceding pages the correspondence in the deve-
lopment of the egg-cell and of the s])ermatic-cell is nearly as complete
as in Ascaris, upon which 0. Hertwiif^'^'' has made a series of very fine
observations. I say " nearly as complete," because here the corres-
ponding zones are not so easy of comparison together as in the case of
Ascaris. We can, however, fallow them in each of the developmental
phases, as we shall presently see.

STUDIES OF REPRODUCTIVE ELEMENTS: T. 13

a. Thr Formative Zonc. — X^ ahove stated this zone is exaetlv
alike in both sacs. The sizes of the germinal cells, their nuclei, and
their chi'c.miatic fibres are so alike in the two sexes, that it would be
difficult to say whether they belona' to an ovary or to a testis. The
oiilv difference between them is that this zone is much shorter in
ovarv than in testis, and tliat more karvokinetic cell-divisions a]-e
preseiil in tlie latter than in tlu' former. HaecJcer^^' was also not
able to see any "^Mitose" in tliis i-co-ion of rlie o\'arv of (7//r'^ryy).s^^ ))iit
he does not hesitate io affirm that sucli occurs liere. A comparison
of figs. 1 and 2 of the testicular sac with figs. 23 and 24 of tlie ovary
will show the resemblance beyond all doubt.

h. The Onvring Zone. — There appears iii this zone a great
difference between the egg- and spermatic-cells, just as in the case of
. l.s\vY?'/.s. of wliich Hertwig^^'^^ says : —

" In diesem zweiten Abschnitt der (reschlectsröhren treten in
der Aiiordnung der Eier nnd Samenzellen erliebliche A^erschieden-
lieiten hervor. Erstere nehmen an (xrösse ausserordentlich zu und
ordnen sicli dal)ei in einfacher Lao-e um eine central o-eleo-ene Rhachis
an. Die Samenzellen dagegen, die sich zwar auch, aber in A'ergleich
zu den Eiern viel weniger vergrössern, sitzen zahlreichen Rhachis-
lamelleii mit Protoplasmafäden auf, "

This difference lietween the egg- and s|K')-inatic-celIs in Diaiitmints
is still greater t^haii in .Iscaris^ where tlie spermatic cells become also
loaded with yolk-graniiles like the egg-cells, and gi'ow to two to foni-
times their original mass, wliereas in JJiap'nnius tlie growth is
very limited. Ihit this difference in size is a ])oint of no great
importance in comparison witli tlie much greafer similaiitv existing
between these two elements, in tlie c<implete disa])pearance of chro-
mosomes and the resting condition of iiuclei in both sexes. Here
again occurs a sliglit diffeivnce between the two in regard to the

1 4 C. IBHIKAWA.

;ibs<eiice or pi'esence of iiuoleoli, :is stated ahovc, and tliis T lliiuk we
shall be able to explain hy tlie difference in growth between the two
kinds of cells.

c. Tlu Zone of Wpeuiug. — This is the most important zone for
us, because we find here in l)<)tli egg- and spermatic-cells a kind (^.f
cell-division that we find nowhere else. This is the occnrrence of
tivct successive nuclear dirisinns witliouf <ni inteyrcniiuj restiuij sinije ami
the reiluction into li alt of the miinher of chroinoso}nes in the seeond of these
divisions.

As observed first liy Plainer,^'^^^ so for as my knowledge goes,
and recently to a mncli greater extent by Hertivig^^^^ in Ascaris
inegalocephala, there occurs no case of such a division exce])t in the
U'enital cells, so that these processes cjin rightly be looked upon as
corresponding stages of tl\e egg- and spermatic -cells ( l^hitner, Hertwig).

'Ilie nuclei that haA^e been resting for some time in the last stage
beoin to be active in this stao-e. Tlie chromosomes gradually come
int(^ yiew and liegin to arrange themselves in a circle under the
infliiencc (?) of the attractive centres which also now appear. The
number of chromosomes I counted to lie eight. In the sjiermatic cells
we can follow the steps from their dissolution and their gra.dual
shortening till the formation of dumb-bell shaped figures. Ihit in the
case of eggs the first distinct appearance of the chromosomes sliows
them already to be in that form. The division of these pi'oduces two
cells of ecpinl size in the case of the male elements, while in that of
the female one of the resulting cells is much larger than the other, and
thus are produced the egg and the first polar body. In all cases, how-
ever, the resulting cells contain each eight single chromosomes. The
nuclei of these cells do not, as said before, go through tlie resting stage
usual with a karyokinetic cell-division, but hegin to divide iunnrdiatehj
and produce incase of speruiaiic cells fuur cells eacli with four chromatic

STUDIES OF REPRODUCTIVE ELEMENTS: T. 15

elenuntx. In tJie case of Cfigs tliis second division occurs genercdly only in
one of these cells — the egg-cell — , whdc in the other — the first polar body —
this division is suspended, so that there arc noiv fur)ned three cells af
uneqnal sizes — a large, single egg-cell and ttni snudl polar bodies, the first
of whicli contains eight single chromosomes, while the second polar bod g
and the egg-cell each contains oiihj four.

Thus there is ;i complete parallelism between the e^g and sper-
matic cell.'. In both cuses the primary germ cells contain eight single
chromosomes, each of which diyides transversely and produces mariv
daughter cells — s[)ei-m mc>ther-ce]]s of males and oxnm motlier-cells of
females, lliese ctjntnin each eight chroniosrnnes like their inother-
cells. They grow to a certain extent aiid thcii two siiccessi\e cell-
divisions take place in them, in both sexes, without an intervening
restino- stao'e, o-ivino' rise to f(3ur spermatozoa in one case and an ea'a'-
cell with two polar bodies in the other. There can therefore be no
doubt that the eo-o--cell Math two (ov sometimes bv division of tlie first
polar body into two cells, three) polar bodies, corresponds exactly
with four s])ermatozoa derived fr<mi a single sperm mother-cell, which
again corresponds with the egg-cell Ijefore the ibrmati(Mi of the polar
bodies.

4. Fertilization.

During the formation of the second ]x)lar body the sperm-cell ])ene-
t rates into the body of the egg-cell. 'Jlie ])enctrating point seems t()
be quite irregular, but mostly near the place Avhere the secojjd polar
body is placed. I ha\^e given three drawings of freshly laid eggs in the
body of which a sperm cell is ah'cadv present. In fig. 31 we see
at the surface of an (.'<x.i^ tlic sef-ond ])olar spindle, and near it to the
right lies a spermatic nucleus. wlii<-1i lias just ])eiicti-;iic(l into the egg ;

16 C. ISHIKAWA.

a small notch at the surf'ice of the latter shows clearly the point where
it entered. Both the ])oIar spindle and the spermatic nucleus lie in a
common protoplasmic mass. Fig.i. 32 and 33 are drawn from eggs
in the same breeding sac as that from which fig. 31 is drawn. In
l)oth eggs the polar spindle is nearly in the same stage as in the egg
represented by fig. 31, the only difference being that in fig. 33 it lies more
in the centre of the egg, and that the chromosomes are more elongated
than in the (jther. The position of the spermatic nucleus is, however,
in botli cases difierent. In fig. 32 it lies in the same pole of the egg
as that in which tlie ])<>lar spindle is found, while in fig. 33 i^ has
penetrated an opposite pole of the egg. although the path of its penetra-
tion is not to be seen in the figure.

The two nuclei resulting from the di^ ision of the second polar
spindle, the nucleus of the second polar body, and the egg-nucleus, show
o-reat différences in appearance. That of the second polar body re-
mains small and its four chromosomes coalesce into a single mass, stain
xevy deeply bv picrocarmine, haematoxylin, etc., while the nucleus
of rlie egg soon l)ecomes greatly enlarged, and its chromosomes show
distinctlv as four thread-like. A'^-shaped ])odies (figs. 34 and 35).
At first their number is (piite distinct, but so(3n the chromosomes
elongate, become twisted and send out many ])rocesses which an-
astomose witli one another, and their innnber becomes indistinct (fig;?.
36-40). In figs. 34 and 35 the four chromosomes are still cpiite dis-
tinctly to be seen. In figs. 36, 37, and 40 they have begun already
to send out processes, and in figs. 38 and 39 they appear as if broken
up into a great number of elements. (The nucleus on the left of
the fig-ure is in both cases the ea-g- nucleus).

The changes which the spermatic nucleus goes througli after it
has entered into the l)ody of an egg and before its copulation with
the e""'-nucleus, are ahnost the same as those of tlio latter, except

STUDIES OF REPRODUCTIVE ELEMENTS: I. 17

during the firöt stages. At first the spermatic micleiis is relatively
small and generally oblong, and stains very deeply and uniformly
with colouring matters, but soon it shows within it a lighter space
in which chromatic fibres become more or less distinct (figs. 31-
33). At about the same time that the egg-nucleus begins to enlarge,
the spermatic nucleus also swells up gradually, and assumes a spherical
form, always remaininu' a little lari>-er than that of the euü'. The chro-
matic elements are yery distinctly to Ije seen, but they are so much
comoluted that it is \'ery difficult to determine their niunber (figs.
36-4U).

The nuclei of the egg and of the spermatozoa gradually approach
each other till they come to lie close together (figs. 36-49), but the
nuclear memijranes continue distinctly ^ isible up to the stage of the
segmentati(jn of the egg. The clu'omatic elements of the nuclei
gradually pass, during these stages, from their so called resting stage
to a state of activity again, and the indi\idual fibres become more and
more distinct. Tlieir nundjer is howe\er, no I<_)ni>'er four but eia'ht.
AVhether tin's is l)rought aljout l)y the trans\ erse diyisi'jn of the ele-
ments or b\- a loiigitudinal di\isi(ni, 1 am not able to tell. Still 1
thiidv 1 am (piite justified in supposing that this doubling of the
number of chromatic elements before tlie formation of a, spindle is
the same phen«jmen(jn as that oljserved by Flemiiimg^'^ and others in the
division of many animal and vegetable cells, (Flcmmhu/s '' hetero-
typische Form ").

The entire process of the copulation of the two nuclei ii}) to the
beuinninii' of the seu'menhilion will Ik; seen by lookiu"" al liü-s. 36-0'».
Fig. 36 re[)resents <jniy a. small part ol" an egir in which both
nuclei are to be seen lyinu' nl some ili-laiici' from one aiioliier. The
smaller ujtper one is I he egg- nucleus and the larger one helow is tiial (<t"
the spermatozoon ; both are more or less in the *• skein " stage. Fiu". 37

18 C. ISHIKAWA.

show8 the Hinge \u wliich the nuclei are more clo.sely placed
(hail in the one represented in fig. 36, the right smaller one being
the eo'f-nuclens and the left laro-er one that of the siDermatozoon.
Close to the smaller nucleus is seen a small spherical area with a
minute central hody in the middle of it. This evidently corresponds
with the central Ixxly with the attractive sphere around it. In fig.
38 the nucleus of tlie egg in proportion to that (^f the spermatozoon is
relatively larger than tliose shown in figs. 36 and 37, and the four
cliromatic elements are more or less distinctly to he seen. The central
body seems now to have become divided into two bodies lying still
very close to each other. The section represented b}^ fig. 40 did not
pass exactly through the plane of the nuclei, but a little obliquely t<3
it, so that they are seen overlappirig. One of the central bodies, the
lower one in the figure, lies below the spermatic nucleus and is seen
throuo'h it. The central bodies are now quite separated from each other.
Fio's. 41-45 are made from eggs killed with Flcmmincjs
solution of aceto-osmo-chromic acid, the chrcjmatic elements of the
copulating nuclei are very faintly stained by haematoxylin, but
the contour of tlie nuclei, as well as the attractive spheres are
Aery distinctlv to be seen. These are placed in all these eggs, in
contradistinction to tlie eggs shown in figs. 37-40, nearer to those
nuclei which, from their relati\e position to the second pijlar body,
appear to be those of the spermatozoon. In Wg. 41, besides the second
polar body, lying in the body of the egg, there is the first })olar l)ody
which happened Ijy chance to be carried with the egg into the breeding-
sac and came to lie outside the egg-mend )rane, just near the place where
the second polar ])odv lies. The nundjer of chromatic elements within
the first ])olar body is still distinctly to l)e counted as eight. Figs.
42-44 show three successive stages in the nuclear copulation ; and in
fiii'. 45 we see two nuclei closely in contact with one another, while the

STUDIES OF REPRODUCTIVE ELEMENTS: I. 19

sphere.^ of nttrnction nre found at the two poles of the plaiie of contact
of the nuclei, which appear to he more or Jess elongated.

Tlic sections represented hy tigs. 46-55 were all taken from
eggs kilJed with hot 30 ^/o alcohol to vsdiicli a few drops of sublimate
liad hcen added. Tlie chromatic elements and the attractive spheres
are tolerably well to l)e seen, but the central l)ody is not so clear
as in the eo'îi's killed with the incro-acetic acid sohition. Fig-,
46 sliows the two nuclei close to one anothci-. and the central
])odies rather fartlieraway from the nuclei tlian in the case represented
bv tig. 45. Xumer(His aehi-oniati** tibres are also well to be seen
exteri<ling l)etween the central bodies and the nuclei, in which are
seen eight single chromosomes. In fig. 47 which is nearly in the
saine stage as the one ^represented by fig. 46, the eight clnvimatic
elemerits are more elongated. The achromatic fibres from the attractive
sphere on the right of the figure are attached to ])()th tlie nuclei, but
those from the other sphere of attraction are connected oidy with
one of tliem, which tlierefore seems to lie nearer than the other to
tliat sphere of attraction. This is more clearly seen in fig. 48, Avhere
we find the nucleus lying above in the figure to be pulled more by the
central body on the right hand side, and that situtited below more
by the one on the left. The nuclear membrane, moreover, seems to
have been dissolved at tlie pole where the aclu'omatic til)res are
attached. The eiHit more or less elon^'ated chromatic l)0(lies a.re seen
in each of the nuclei. In tig. 49 both the nuclei are ])uiled equally by
the central Ijodies and the chromatic elements are f )nnd lying at the
centre of the spindle, whose achromatic tibres are now found indis-
tinctly within tlie nuclei. The nuclear membrniie is, howeven*, still
present except at tlie ])lace of their contact. Fig. 50 shows a cross
section of the nuclei in cojnilation as i.; rejn'esented by tig. 49. In
tig. 51 the nuclear memljrane has entirely disappeared, but the chro-

20 C. ISHIKAWA.

matic elements belonging to both the nuclei nre still to l^e seen in two
separ.'ite gr(^nps. In these tln*ee sections as well as in those i-epresented
bv the next tliree tignres the nnnilier of the chromatic elements is not
at all clear. Fig. .52 shows a cross section of a spindle at the stage
sliown by fig. 51, more highly magnified. Figs. 53 and 54 are
taken from the same lot of eggs as tliat represented by figs. 51 and 52,
bnt the chromatic elements are fused together at flie equator of tlie
spindle, and are now no more to be distinguished as two separate
groups.

Lastly in fig. 55 is found tlie first segmentation-spindle with
the chromosomes just separating from the ecinatorial ])laiie. Tlieir
nu.mber can be distinctly counted as eight in t\V(i rows, one of wliicli
at tlie riglit hand side happened to be pulled Iw the acliromatic filires
of tlie left, and is seen witli its one end at the riglit and the other at
tlie left.

P.. SUMMARY.

1. The primary sperm cells correspond exactly \Yith the primary
eg^'-cells. lîoth contain eight chromatic elements.

2. In fx^th cells the eight chr<^mosomes become constricted
transversely giving rise to eight dumb-bell shaped bodies. Tliese
arrange themselves m an equatorial zone and begin to di\ide in such a
manner that half of each clu'omosome goes to one cell and the other
half to the otlier. Tins kind of cell-division takes place two or
three times and the resulting cells fn-m the mother cells of eggs or
sperniatt)Zoa, as the case may be,

3. These grow consideralily ; after which

4. They begin to di\ide as ])efore ; each chromosome dividing

STUDIES OP REPRODUCTIVE ELEMENTS: I. 21

transversely. This stage corresponrls in the egg to the formation of
the first polar hody, which takes place exactly in the same manner as
that of the first division of the sperm-mother cell. En hoth cases the
original eio-ht chromosomes hecome divided into two, giving rise to
the dauirhter cells also coiitaininii* eiii'ht clu-oniosomos (Wn^waim^^
" Eqiiationstheilnng ").

5. This is immediately followed ])y another division, witliont
an intervening resting stage of the rniclei, and 1)y reduction in the
original number of chromosomes (^Weismann\s " Redulctionstheilung '*).
The eight chromosomes which at first are arranged in a single row
become arranged in double rows of tour each, and the cell begins to
divide in such a manner that four chromosomes go to one cell and the
remaininii' four to the other.

]')y divisions described under Xo. 4 and 5 u s])erm-mother cell as
well as an egg-mother cell increases to: four cells, which in case of the
former give rise to four spermatozoa, while in tliat of the latter a single
egg cell with two polar bodies, results (or tlu'ce when the first polar
body divides).

6. During the formation of the second polar 1)ody the spermatic
cell enters into the egg-cell. The nucleus of the sperm cell is, as a
general tlu'ng, at first rather small and ('(flours deeply and homogeneous-
ly, but soon the diiferentiation sets in and the four chromosomes become
distinctly visil)le. The nucleus of the egg-cell remaining after the
formation of the secoijd polar Ijody — tlie female pronucleus of Ed. van
Beneden — shows at first distinctly four elements. These soon grow
longer, show many convolutions, and pass into a " skein " stage.

7. The two nuclei gradually approach one another until they
come in close contact, but they do not unite into a single piece before
the equatorial plate is formed. The number of chromatic elements in
each of the copulating nuclei is now found to be eight, exactly double

22 C. ISHIKAWA.

the number present in the maternal nucleus after the expulsion of
the second polar body, and in the ripe spermatozoon.

This number goes unchanged to tlie formation of the first
segmentation spindle, which gives rise to two first segmentation
spheres, each of which contains eight single chromosomes.

C. THEORETICAL COXSIDERATIOKS.

Since the important publications of Anrrhach/^ Ed. van BcnciJcn,
Bilt.^clili. the Hrrhvig.'^, Fol, etc., investigations on the phenomena of
fertilization ha\e bec<yme more and more interesting, and now after
the well known theoretical treatment of tliis and other kindred
subjects l)v Trof ]Vei>!)iiann,^-"^ the formation of genital cells, tlieir
phases of ripening, find their copulation require exact and thorough

study.

The most complete work iri this direction is the beautiful
investigation of 0. HerHoig on the " \'ergleich der Ei und Samen-
bildung bei Xematoden," published al)out a year ago. In this work
is o-iven for the first time a clear insight iiito the exact iinralielism
existing between the egg and the sperm-cells, the mode of their
development, etc., e\'ery point in which corresponds so exactly with
the descriptions given in this paper, that it seems almost superflii("»us
for me to have published them. I have deemed it, however, worth
while to record the results of my own investigations because the con-
clusions arrived a.t 1jy Hertwig are regarded by some authors as
demanding explanations other than those he has found for them.

There are, so far as my knowledge allows me to judge, three
modes by which the " Reduktionstheilung" of sexual cells takes place.
Platiier'-^^'^^-'' in liis vari<:ius important publications on the sexual cells
mentions an exceptional ukmIc of cell-division in the last diNision of

STUDIES OF REPRODUCTIVE ELEMENTS: I. 23

s[)erni cells and in the formation of the second polar body. He there
.say.s : " Das allgemeine Schemn für die Zelltheilung verlangt, dass der
Kern nach der Theilung wieder in das Ruhestadiam zurückkehrt, das
heisst sich ans dem Aster der Knäuel und aus diesem das Kerno-eriist
wieder rekonstruiert, und so ündet man es auch iil)erall. Nur in zwei
Fällen findet hiervon eine Ausnahme statt. Der erste betrifft die Bildung
des zweiten liichtungskörperchens u.nd ist genügend bekannt. Es wird
hier das Kiihestadium übersprungen. Aus der innern Tochterkern platte
der ersten Richtungsspindel bildet sich sofort die zweite Richtungsspin-
del, und auch die in das erste Richtungskörperchen übergegangene Kern-
hälfte zeigt iiäutig das gleiche \ erhalten, das heisst sie bildet sich gleich-
falls sofort wieder zu einer neuen Spindel in entsprechender Weise um.
DieTlieilung der zweiten Riditungsspindel wird dadurch zu einer
ReduktioDstheilung in Rezug auf die Quantität des Kernmaterials. Der
zweite Fall dürfte weniger bekannt sein ; er l)etrifft die letzte Theiluno-
der samenbildenden Zellen. Auch hier wird das Ruhestadium über-
s])rungen. Die letzte Theilung schliesst sich direkt an die vorhergehende
an, indem sich aus der Tochterkernplatte sofort die neue Spindel bildet.
Also auch hier findet eine Reduktionstheilung der Masse nach statt."
He has thus, for the first time, clearly shown the truth of Weismann s
theoretical ccjnclusion as to the necessary occurrence of a reducti(3n of
nuclear elements at the fjeginning of each ontogenesis. In his well
known essay on tlie ''Zahl der Richtungskürper," etc. Prof. IVeisiiiann,^-^''-
after discussing the subject of copulation, where the ancestral plasma
ought to be doul)led at ea<'h process, sees the necessity of its reducti(>n
to half of its original mass. The sharjt insight of Weisinann has
brought out from can Boicihnis and Caruoii's work the necessity of
admitting the ]'e(|uired rnluction in tlie formation of thesecoiid polar
body. He says : " In der Ausst<3ssung der zweiten Richtungskörpers
aljer wird mit Kecht eine Keduktionstlieihuig erblickt werden, durch

24 C. ISHIKAWA.

welche die Hälfte der verschiedenen Ahnenkeimplasmen in Gestalt von
zwei Kernschleifen aiisgestossen würde." In another place he says:
" Sollte ich mich aber selbst in dieser Deutung irren, so scheint mir doch
die theoretische Forderung einer bei jeder Generation sich wiederholen-
den Keduktion der Alinenplasmen so sicher begründet, dass die Vor-
sränfj'e, durch welche dieselbe bewirkt wird, "-efunden werden müssen,
wenn sie auch in den bis jetzt bekannten ïhatsachen noch nicht
enthalten sein sollten."

This assumption of Weismann of a reduction of chromatic
elements in the second polar body in the eggs of Ascaris and iir
general, is now in a wonderful way proved by 0. Hertwig,^^'^ whose
beautiful moriograjjh lias gi\en me so much pleasure that 1 have read
it over and o\ er again, the more so, since his results are in exact par-
allelism with those obtained by myself in studying the sexual cells
of Diaptomus, as stated aljove.

Thus the observations of /Va//;e/-,"'"^^ Jlcrlwifj"-' ;ind myself show
clearly that there is a kind of nucletir division in the formation of tlie
second p(jlar body as well as in the last cell division in spermatogenesis
which is quite diiferent from tlic ordinary karyokinesis, and wliich takes
place in perfect accordance with ]]^eisiiianii's A'iews.

BoV('ri also sees the necessity of admitting the " Reduktions-
theilunf " at each ontogenetic stage, but he lets tliis take place not
in the formation of the polar l)odies, but betöre it. On page 0)2 of his
" Zellen »Studien, lieft 3," he says : —

"Wann die reduzierte Cliromosomenzalil zuerst auftritt und wie
die Reduktion zustande kommt, dafür besitzen wir noch sehr wenige
Anhaltspunkte. Retrachten wir zunächst die Eibildung, so können
wir niu- den einen S;itz als sicher und allgemein gültig auf-
stellen, dass die Heduktioii spälcstcns Im Keimbläschen erfolgen muss.
Denn bei der IJilduug der ersten Richtiuigsspindel kommen die Chro-

STUDIES OP REPRODUCTIVE ELEMENTS: I. 25

mosomen liereits in der reduziei'teii Zah] zum \ orsdiein. Fnlls also
Weismanu seine theoretische postulierte Keduktion der Z-dd der Ahnen-
])lîismen mit dieser thatsächlichen Iveduktion der Zahl der Chromos(j-
men identifizieren will — ^Yas rdcht nothwendig ist — so niuss er die
Annahme, dass dieselbe durch die l>ilduno- de.-! zweiten Hichtungsk()r-
j)ers vermittelt werde, aufgeben."

But as the observations of Bovcri on this point in Ascaris were
proved not to hold true by the above cited investigation of Hertwig,
T will not treat of it again here, but will oidy refer the reader to his
I )ea utiful monograph.

The latest series of ()l)servations come from Hacchcr'''^ arid Ileuh-
m^,'"'^"' botli of whom also admit the introduction of a re<luction of
chromatic elements at the Ijeoinnino' of each embrvou'enesis. Thev
admit, however, this to take place in the formation of the first polar
body and not in tliat of the second. Haechcr who studied the formation
of the polar bodies in Cijchps gives a couple of very fine woodcuts, which
lead one to think that the " Jieduktionstheilung " takes place in the
formation of the first polar body. xVs in the case of Diaptomus, the
chromosomes in the sexual cells of Ctidops number eight. These
divide longitudinally in stage A, and produce sixteen elements, every
two of which lie close together and thus form eight groups of double
elements. In stage ]>, they liecome se])arated into two groups each of
four double elements, one of which serves f(n' the formation of tlie
first polar body. The remaining four double elements now arrange
themselves to form the second polar spindle (stages C and D). Haeckcr,
however, quite rightly d(^es not regard his observations as to the
stages in which the " Reduktionstheilung " takes place as conclusive.
After discussing the possil:)ility of Booeri's discoveries in eggs of Timm.,
Echinus, Garinaria, Pterotracliea, and Fhyllirrhoi being in accordance
with his own view, i.e., that the " Reduktionstheilung " takes place

26 C. ISHIKAWA.

duriiio- the formation of the polar Ixnlies, he conchides : — •

"Die Reduktion findet also wälirend der AuHstossung der Rich-
tungskörper statt und es fragt sich niuinieln-, welches Stadinm im
Speciellen die Reduktion darstellt.

"Die nächstliegende Dentnng der \'erhältnisse wird wohl fol-
gende sein : die Längsspaltung der Chromosomen im Stadium A ist
geAvissermassen eine anachronistische, d. h. die normalerweise in der
Aequatorial platte der zweiten Richtungsspindel stattfindende Längs-
spaltung der Chromosomen, in gewöhnlichen Fällen also die secun-
däre, wurde in die Aequatorialplatte der ersten Spindel zurückverlegt,
ein Vors-ano-, der nach lîoveri's Befunden nichts Auffälliges hietet.
Sieht man also ah von dieser (secundären) Längsspaltung, so
übernimmt die erste Spindel aus dem Keimbläschen die ursprungliclie,
nicht reducierte ÄcJitzahl der Elemente, um von diesen durch einen
besonderen ^"ertheilungsprocess vier in den ersten Richtiuigskörper,
vier in den Eikern abzuscheiden, ohne dass die primäre Verdoppelung
der Schleifenzahl, wie sie sonst der ersten Spindel zukommt, auftritt.
Nach dieser Deutung fände also die Reduktion bei der Ausstossung
des ersten Richtungskörpers statt.

" Man kann ahev den Thatsachen noch eine andere Deutung
geben : die Spaltung der acht Chromosomen in Doppelfäden würde
der primären Längsspaltung der Elemente entsprechen. Auch diese
Deutuns' schliesst einen abweichenden 'Jlieilungsvorgang schon in der
ersten Spindel in sich : anstatt dass jeder l\3l V(^n jedem Doppelfaden
je ein Tochterelement an sich zieht, findet nach jeder Seite die Ab-
scheidungf von vier Paaren von Tochterelementen statt. Die vier im
Ei zurückgebliebenen Paare liefern dann die acht einfichen Ele-
mente, welche in der zweiten Spindel zu je vieren nach den Polen
derselben attrahiert werden. Diese Deutung würde die eigentliche Re-
duktion also erst in die zweiten Spindel verlegen,'^

STUDIES OF REPRODUCTIVE ELEMENTS: I. 27

Thus while HcerJccr allo^vs the proljul)iIity of the occurrence of
a " HeduktioiistheiJuijg " in the formation of either the first or the
second poJar hody, Henkiiig is quite decidedly of the opinion that this
division takes place in the forniatiou of the first polar hody. In his
latest work on Pynlwcoris ajttcrns, L. he gives a detailed description
of the formation of spermatic elements and polar bodies, in which he

"1) Den Ursamenzellen entsprechen die Ureier. ]>eide Zell-
formen enthalten die für die Körperzellen charakteristische Zahl von
24 Chromosomen.

" 2) Den unreifen Eiern cnisprechen die Sanienmuttei'zellen
(Spermatocyten I. Ordn.). Ikide wachsen erheblich heran, in beiden
kommt es zur Ausljildung' eines \erhältriissmässig grossen bläschen-
förmigen Kernes, in beiden werden Dotterkiigelchen erzeugt.

" 3) Die Absclmürung des ersten Richtungskörperchens entspricht
der ersten Theilung der Spermatocyten. In beiden Füllen kommt es
zu einer (Weismann'sche) Keduktionstheilung, indem sich die Chro-
mosomen ,, zwei reichig " aufstellen und zu je 12 Elementen in die
neuen Zellen übergehen. Die typische Zahl 24 wird also hier durch
einfache Trennung der chromatischen Elemente auf 12 reduciert.

" 4) Die Ausbildung des zweiten Eichtungskörpers entspricht der
zweiten Theilung der Spermatocyten. Die 12 chromatischen Elemente
werden unter lîeibehaltung der Zahl durch Aequationstheilung direkt
halbirt, ohne dass sich das Stadium eines ruhenden Kernes dazwischen
einstellte. Die sofortige Theilung der Spermatocyten II. Ordn.
wurde möglich, weil die vorhergehende erste Theilung nicht als
normal anzusehen ist und weil die letztere wahrscheinlich bewirkte,
dass sich gleich die auch für eine zweite Theilung nöthige (also
doppelte) Zaid chromatischer Fäden an die Chromosomen anheftete."

HcnlciiKi tries also to make his observati<3ns coincide with those

28

C. ISHIKAWA.

of Heriwig upon Ascaris by giving different interpretations to the results
obtained by the latter investigator. AMiatever may be the interpretation
in the case of Ascaris, my own case, given above, can not to my
mind be made to coincide with his observation on Pyrrhocoris, I will
not, however, assert the " Keduktionstheilung " in the formation of
the second polar body and in the last cell division in the spermatogenesis
to be the universal rule until a sufiicient number of observations be
obtained in other groups of animals and perhaps of plants too.
Theoretical considerations concerning the phenomena of fertilization
lead us in all probalDility to the " Keduktionstheilung " as occurring
in the second polar body and in the last division of spermatic cells.

I will now consider very shortly the phenomena of fertilization.
As stated above, tlie maternal and paternal nuclei do not unite into a
single segmentation nucleus, as Hertiüig^^~^ for the tirst time gives
out, but remain separate from each otlier till after the complete forma-
tion of the segmentation spindle. Something of the kind had been
already observed l^y \arious ^vritery, Ijut this fact was brought out in
its full light only by the last work of Ed. ran Bencden and Jul in *^-'
on Ascaris. In the eggs of a, c(jpepod Crustacea (Cetocliilus) Grohben-^'
observed for tlie -first time, that the two nuclei do not become united
with one another and form a single segmentation luicleus, but
" stossen die Ijeiden Kerne, Eikern und Spermakern, aneinander und
sind nur noch durch eine zarte Wand voneinander geschieden. Auf
dieses Stadium folgt sogleich die Bildung der ersten Kernspindel."
But above all, the recent valuable investigations of B over i^^^ on this
head in various groups of animals, as well as his enumeration of
facts obtained by previous workers, make us accept this as the rule,
and the perfect union of both the nuclei as exceptional cases only. To
these we may add the observations of Henliincf^^^ on the eggs of Fieris,
as well as that of Hmcher''''^on Cijclops. My own observation on the

STUDIES OF REPRODUCTIVE ELEMENTS: I. 29

conjugation of Noctihica^^*^ can also be looked upon as a further con-
tribution in this hne.

Science College, End of May, 1891.

List of References.

* Auerbach, L. — Orgauologische Studien. Breslau, 1874.

1. van Beneden, E. et A. N'eyt. — Nouvelles recherches sur la fécon-

dation et la division mitosique chez l'Ascaride mégalocéphale.
Bullet, de l'Académie royale de Belg., 3 "^^ Sér., t. XI V. 1887.

2. van Beneden, E. et Julin. — La Spermatogenese chez l'Ascaride

mégalocéphale. Bulletins de l'Académie royale de Belg.,
S"^' Sér., t. XIY. 1887.

3. Jjoveri, Th. — Zellenstudien. Heft 1. Die Bildung der Rich-

tungskörper bei Ascaris megalocephala und Ascaris lumbri-
coides. 1887.

4. Ijoveri, Th. — Zellenstudien. Hett 2. Die Befruchtung und

Theilung des Eies von Ascaris megalocephala. 1888.

5. Bijveri, 'ili. — Zellenstudien. Heft 3. Lieber das \'erhalten der

chromatischen Kernsubstanz bei der Bilduno- der Hichtuno-s-
körper und bei der Befruchtung. 1890.

6. Bütschli, U. — Entwicklungsgeschichtliche Beiträge. Zeitschrift

f. wiss. Zoologie, Bd. 29. 1877.

7. Fleiuming, W. — Xeue Beiträge zur Ivenntniss der Zelle. Arch. 1'.

mikrosk. Anat. Iki. XXIX.

8. Grobben, C. — Die Entwicklungsgeschichte von Cetochilus sep-

tentrionalis Goodsir. Arbt. aus dem zool. Inst, der Lniv.
Wien, Tom. III.

9. Haecker, V. — Uel^er die Reifungsvorgänge bei Cyclops. Zool.

Anzeiger, Xo. 346. 1890.

30 C. ISHIKAWA.

10. Heiiking, H. — Untersuciiungen über die er.sten Entwicklungs-

vorgänge in den Eiern der Insekten.

I. Das Ei von Pieris V)rassica3 L., nebst Bemerkungen über
Samen und Samenbildungen. Zeit. f. wiss. Zoologie, Ikl. 49.

11. Henking, H. — Untersuchungen über die ersten Entwicklungs-

vorgänge in den Eiern der Insekten.

II. lieber Spermatogenese und deren Beziehung zur Ei-
eiitwicklung bei l-'yrrhocoris apterus \j. Zeit. f. wiss.
Zoologie, Bd. 51.. Heft 4. 1891.

12. Hertwig, 0. — Beiträge zur Kenntniss der B)ildinig, Befruchtung,

und Theilung des thierischen Eies. Morph. Jalirb. 1875,
1877, 1878.

13. Hertwig, 0. — A'ergleich der Ei- und Samenbildung bei JSTema-

toden. Archiv für mikroskopische Anat., Bd. 36. 1890.

14. Ishikawa, C. — Vorläufige Mittheilungen über die Conjugations-

erscheinungen bei deri Noctiluceen. Zool. Anzeiger, No.
353, 1891.

15. Ishikawa, C. — On a development of a fresh water macrurous

crustacean. Quart. Journ. of Micr. Sei., vol., XXV.

16. Mayer, Paul. — Zur Entwicklungsgeschichte der Decapoden.

Jenaische Zeitschrift., Bd. XI.

17. Xussbaum, M.— Bildung und Anzahl der Bichtungskörperchen

bei Cirripedien. Zool. Anzeiger, 1889.

18. Blatner, G. — Beiträo-e zur Kenntniss der Zelle und ihrer Theil-

uno'serscheinuno'en. Arch. f. mikrosk. Anat., Bd. 33.

19. Blatner, G. — lieber die Bildung der Richtungskörperchen.

Biolog. Centralblatt, Bd. 8. 1888/89.

20. Weismann, Aug. — lieber die Zahl der Richtungskörper und über

ihrer Bedeutung für die Vererbung Jena. 1887.

Explanation of the Plate.

DiaptoiuK!^ sp. Î-

Fig. 1. — Lougitiidinal section of a testis : the lower end repre-
sents the formative /one and tlie np]^er end is tlie place where the vas
deferens takes its origin. Y TIT x Seibert = 120.

Fig. 2. — The formative zone of the testis represented by fig. 1.
more highly magnified. A karyokinetic; figure at the right is drawn
here from the corresponding part of another animal. yVII x Sei-
bert = 850.

Figs. 3~o. — Uepresent successive stages after the last division of
the cells in the formative zone. Y VIT x Seibert = 850.

Fi(js. 6-8. — Cells from the formative zoiie. In figs. 6 & 7 the
eight chromosomes are still long and are difficult to count. In fig. 8
the chromosomes are much shortened in the cell on the right hand
side. 7 VII X Seibert = 850.

Fi(is. 9, 10, cC- 11. — Show the first division of the sperm-mother
cell. Fig. 9 is drawn from a specimen killed with picro-acetic acid,
and coloured with hematoxylin. Three of the eight dumb-bell shaped
chromosomes are seen on this side and five others on the other side.
Figs. 10 and 11 are specimens killed with methyl -green-acetic acid.
In both figures the eight chromosomes lie on the periphery of a circle
and in both (^f them five elements lie on one side and the three others
on the other. All drawn by Seibert Y^^H ^md magnified 850 times.

Figs. 12-16. — Sliow the second division of sperm-mother cells
immediately following the last division without an intermediate resting

32 C. ISHIKAWA.

stage. Figs. 12 & 14 sliow a stage just after the first division : eight
single chromosomes are still in a single plane. Fig. 13 is the polar
view of the same. Fig. 16 represents a stage a little more advanced
than those of figs. 12 & 13. in whicli eight chromosomes lie in two
circles of fonr each . Fig. 15 is more advanced nnd the cell itself has
now begun to divide. Figs. 12-15 are drawn from specimens killed
with picro-acetic acid, and fig. 16 with acetic acid methyl-green.
All drawn by yVlI Seibert = 850.

Figs. 17-22. — ^l^ast changes in the formation of spermatozoa.
Fig. 17 is just after the sec(^nd division of the s])erm-mother cell. The
nucleus is now fouiid to stain homogeneously. In fig. 18 a cell on
the left shows a vacuole in the micleus ; in the other two cells, as well
as in that of tig. 19, traces of chromosomes are more or less distinctly
to be seen. Fig. 20 shows two cells in which a big vacuole ap-
pears. In fig. 21 chromatic elements have become more distinct than
in figs. 18 (two cells on the right) and 19 : \\\Q nuclear membrane has
become more or less indistinct. Fig. 22 represents four spermatozoa
found in the vas deferens. All drawn l\y yVII x Seibert = 850.

Figs. 23 du 21. — Represent the posterior ends of two ovaries. In
fig. 24 the extreme end is iiot represented, lîoth drawn by Seibert
VY-33.

Fig. 26. — Two eggs just befrre the formation of the first polar
body. Iri both of them are seen eight dumb-l)ell shaped chromosomes
scattei-ed rather irregularly in the germinal vesicle. In the germinal
vesicle of the eo-o- on the left, a nucleolus and a number of small
circular bodies — -the micro- nucleoli — are seen, while in that of the
^%^^ on the riglit the inicleolus is no more t(^ be seen. This figure is
compiled from three successive sections, y A" x Seil)ert = 330.

/•V^.s. 26-29. — First polar spindles. Figs. M, 28, and 29 repre-
sent tlie side view and fig, 27 the polar view. The nuclear membrane

STUDIES OF REPRODUCTIVE ELEMENTS: T. .^.S

has already disappeared nnd tlie ci'o-lit clnvnnosomes lie in a. ring.
Figs. 26-28 were treated with lii)t-alcohol-.sul)liiiiate and the achro-
matic fibres are not to be seen. In tig. 29 tlie achromntic fibres are
well represented. All draivn witli Seiberî^ Y^'TT"^^*^*^-

Fifi. SO. — .\ small snperficiïil portion of aii egg, just after the
fni'ination of the tirst polîir Ijody, and the second poLu* spindle is seen
from a pole. Eight short cliromatic elements are seen in a plane at the
e<[uat<)i- of the spindle which is not represented in the figure. Seibert
VVII-850.

Figs. 31, 32. d'-SS. — llepresent tlirce sections in which the second
polar spindle ;md a spermatic nucleus wre present in the egg, and in
relatively different positions. In nil iiu^ spindles the fonr chromosomes
are more or less distinctly to be seen, b'igs. 31 and 32 are drawn
by Seibert VV = 330 times, nnd fig. 33 by Seibert VVII = 850 times.

Figs. 34 é 35. — Division of the second polnr spindle is nearly com-
plete, and the egg-nucleus has swollen up a little. The four chromo-
somes are now more or Jess elongate 'd. I'.otli drawn with v^eibert
VVII = 850.

Fig. 36. — Piece of an egg in wliich the second polar body, the
egg nucleus, and the spermatic luideus wve present. The four chromo-
somes in the egg-nucleus are nuich elongated and jue joined togethei-
by " Lininfaden." The spermatic nucleus is now much larger than
the egg- nucleus. Seibert Y ¥11^^850.

Fig. 37. — The copulating nuclei out of an egg, the larger of
which represents tlie spermatic and the smaller the egg nucleus. At
one pole of the egg-nucleus is seen a small central body with an
" archoplasma " around it. Seibert 7 VI [ = 850.

Figs. 38-55. — Represent various stages of copulation and the first
segmentation spindle of an egg. In tig. 38 is seen the second polar
body at the left hand upper corner. Tlie two nuclei are approaching

4% C. ISHIKAWA.

one another. Xerir tlie smaller one — the e_2"2'-iiuc]ens — is seen two
centrosome.-^ not widely separated from each other. In fig*. 39 the nuclei
are much larger and the central bodies now lie between them. In
fig. 40 the section did not pass exactly in the plane of both
nuclei, which therefore are seen as overlapping one another. These
three figures are draAvn from s])ecimens killed witli picro-acetic acid
solution. Figs. 41-45 are drawn froin sj^ecimens killed with Flem-
ming's solution. In fig. 41, the first polar body is l)y charice seen
lying outside the egg-membrane. Figs. 46-55 are drawn from speci-
mens killed with hot-sublimate-alcohol. In figs. 46 and 47 the two
nuclei have still a distinct membrane. In both of them we see eight
chromosomes. The sizes of the nuclei are still a little different from one
another. In fio-. 48 the nuclear membranes have become somewhat
indistinct, and the nuclei themselves are more or less drawn by the
attraction spheres. The relative positions of the latter and the nuclei are
very interesting in regard to the manner in whicli the nuclei are drawn
by the attraction spheres. In fig. 49 the two nuclei are drawn equally
by the attracti(3n spheres, and the chromatic elemerits lie at the
equator of the I'pindle. Fig. 50 represents a transverse section of such
a spindle. In tig. 51 the nuclear membranes have disappeared com-
pletely, but the chromatic elements of both the nuclei are still lying-
separated from r,ne :inother. Fig. 52 represents a transverse section of
such a spindle more highly magnified. In fig. 53 and 54 the two
groups of chromosomes are no longer distinct from one another.
Lastly in fig. 55 the chromosomes have just begun to separate from
the equatorial plane into two new groups, each consisting of eight
elements. All these figures are drawn with Seil^ert yV = 330, with
the exception of Figs. 52 and 55 whi(;h are drawn with Seibert
7 VII = 850.

Further Studies on the Formation of the
Germinal Layers in Chelonia.

(Contributions to the Embryology of Reptilia III).

By

K. Wlilsukuri, Ph. D., Riéakuhakushi.
Professor of Zoology, Science College, Imperial University, Tokyo, Japan.

With Plates II.— IV.

Some yenrs ago conjointly with Mr. Ishikawa, I published a paper
on the Formation of the Germinal Layers in Chelonia (No. 1). Our
observations were then made solely on Trionyx japonicus,
Schlegel. Recently I have had an opportunity of studying the earlier
stao-es in the development of CI em my s jnponicn. Grnij. The
results of my observations in tlie latter species confirm onr vicavs on
all essential points. Jn addition. I have been nble to elucidnte more
fully the earlier phases in the formation of the mesobJast not only in
Clemmvs l^ut also in Trionyx. These, in my opinion, lead to
conclusions of considerable importance and deserve the attention of
those who are engaged in the study of the vertebrate development.

The materials for the investigation were as before obtained from
tortoises which breed freely in captivity. As each deposit of e^^r^
was marked as it was' laid, I had an unusual opportunity of obtaining
a complete series of embryos. In some cases, T took egg^ out of one
deposit at several different times, in order to determine more ac-

36 K. MITSUKURI.

curately the succession of the changes that take place.

On the present occasion, I shall not touch on the formation of
the mesoblast or mesenchynia at the periphery of the blastoderm an
account of which, I reserve for a future paper.

Clemmys japonica, Gray.

The earliest stage in my possession was obtained from the eggs
opened directly after they were deposited. The blastodermic region,
owing to its lighter specific gravity, is always found at the upper pole,
in whatever position an egg may happen to have been deposited.
Surface views of the blastoderm are represented in Figs. 1 and la
(PL II). It corresponds to that shown in Figs, la and lb of the paper
on Tri onyx (No. 1) but is somewhat younger. The blastoderm
shows a comparatively large pellucid area, in which the embryonic
shield is placed excentrically, nearer its posterior edge, and is joined to
this edge by irregular opat^ue patches. The most conspicuous
feature in the dorsal view of the embryonic shield (Fig. 1) is the
dorsal opening of the blastoporic passage. It is placed in the
median line near the posterior end of the shield, and is a crescent-
shaped, transverse slit, the concavity being to the front. The
embryonic shield shows indistinctly two concentric zones which are
most marked in front and at the sides. The innermost area is the
most opaque part of the blastoderm. Xear the front edge of this area,
there is however a somewhat less opaque area which corresponds, it
will be seen, on referring to the ventral view (Fig. la), to the ventral
opening of the blastoporic passage. In the same view (Fig. la), the
innermost ;ind most opaque area is seen to be the thick part through
which the l)lastoporic passage leads from the dorsal to the ventral
opening.

The minute structure of this early stage will become clear from

FURTHER STUDIES ON THE GERMINAL LAYERS ETC. 37

"a study of Fig«. 5 and 5a (PI. Ill, a longitudinal section) and
Figs. 6-10 (a series of transverse sections).

Fig. 5 is a longitudinal section of this stage, near the median line.
The blastoporic passage is very conspicuous, beginning at the dorsal
surface and leading obliquely forwards to the ventral surface. There
is a marked difference of structure between the part of the blastoderm
in front of the passage and that lying b e h i n d it. In front of the
passage, there are only two layers : the epiblast and the primitive hypo-
blast. The epiblast is already a well defined sheet, extending beyond
the area included in the figure — though how much beyond I have not
ascertained. In the transparent area in front, it is a thin layer con-
sisting of pavement cells ; as we trace it posteriorly however, the cells
become taller, changing gradually from the pavement to the columnar
shape. In the region directly in front of the dorsal opening of the blas-
toporic passage, the nuclei are in several strata, although the epiblast
seems to consist in reality of only a single layer oftall cells. As regards
the lower layer or primitive hypoblast, it is, in the anterior transparent
area, a loose layer of cells containing many fine yolk-granules (Com-
pare Trionyx l\o. 1, Fig. 15). In front it passes into the bed of yolk
in which nuclei are seen. Traced backwards, it becomes at first only
two or three cells deep, and then suddenly quite thick as we reach the
outer of the two concentric zones seen in the surface view of the em-
bryonic shield. The cells here are arranged in a loose network, with
large meshes. Further backwards, the lower layer is formed of
columnar cells and assumes an appearance like the superjacent epiblast.
It is thicker, however, and seems to l)e formed of severid layers of cells.
At the anterior dorsnl lip of the l^lastoporic passage, the epiblast
becomes continuous with the primitive hypoblast.
^ In that part of Fig. 5 (or Fig. 5a) showing the region behind
the blastoporic passage, there is a different state of things. Beginning

':38 K. MITSUKURI.

ß.t the hindmost part, the epiblast is already formed as far hack as is
given in the figure. As we trace it forward, it is distinct up to the
blastoporic passage, but here it becomes merged in a large thick mass
of cells whicli stretches jilong the floor of that passage. The lower
layer, which is continuous behind with the yolk-bed and which is
distinguished by containing a larger quantity of yolk granules, is also
joined to the large mass on the floor of the blastoporic passage by
irregular reticulate strands of cells. Thus, behind the blastoporic
passage the layers are fused together, and there can be no doubt that
the thick mass of cells is the beginning of what Eabl calls the per-
istomal mesoblast.* Eventually it will stretch backward for the space
of 180° like an open fan, between the epiblast and the definitive hypo-
blast.

Figs. 6-10 are a series of cross-sections from another embryo in the
same stage, arranged from behind forward. They confirm what we
have learned from the longitudinal section and give us some additional
information.

In Fig. 6, taken from directly behind the blastoporic passage, the
epiblast is marked by a groove at about the median line, and is at this
point proliferating downwards cells which form a small mass con-
tinuous with the lower layer by loose strands of the cells. This pro-
liferation is seen more or less distinctly in several c(jnsecutive sections
until it joins in front the large mass on the floor of the blastoporic
passage. This median liiic of proliferation I take to be the commencing
primitive streak. This becomes broader îind more conspicuous in later
stages. The same thing was seen in Trionyx (Joe. cit., Figs. 6
and 8).

In Fig. 7, the epiblast is no longer distinguishable in the median
region, Avhich is occupied by the solid thick mass of cells already

* C. Ra,bl :-^Theorie des Mesoderms. Morph. Jahrbuch, 1889.

FURTHER STUDIES ON THE GERMINAL LAYERS ETC. 39

. noticed in the longitudinal section. There becomes established later on
at this place the yolk plug, as reference to Fig. 22 will show, and
as has been proved sufficiently, I think, in the case of Trionyx
(loc. cit.).

In Fig. 8, the section passes through the blastoporic passage
which is, however, still open above on the left. The floor of the
passage is proliferating cells below.

In Fig. 9, tlirough the front part of the ventral opening of the blas-
toporic passage, the cells of the lower layer are arranged in the median
line in a regular columnar epithelium. This is what is usually known
as the chorda-hypoblast, although, as I shall show in the sequel, it gives
rise to something besides the chorda dorsalis. Laterally the chorda-
hypoblast becomes continuous with loose irregular reticulate masses of
lower-layer cells containing a large quantity of yolk granules. Still
more laterally the lowei' layer is reduced to a very thin sheet corres-
ponding to the transparent region of the surface view. Outside of
this it becomes continuous with the bed of yolk -matter.

As we trace the series of sections forward, the part of the lower
layer showing a regular columnar arrangement becomes smaller aud
smaller, the loose netw(jrk-like part encroaching gradually on it.
Columnar cells remain longest on the lowest stratum of the median
part (Compare Trionyx, loc. cit., Figs 13 and 14).

In Fig. 10, the whole lower layer hi the regicjn of the embryonic
shield consists of a loose network of cells.

This embryo thus consists almost entirely of only two layers, the
epiblast and the primiti^ e hypoblast. The only part which we can
distinguish as the commencing mesoblast is a median mass of cells
found behind, and on the floor of, the blastoporic passage, continuous
above and below^ with the two primary layers. In front of the blas-
toporic passage, the chorda-hypoblast is being gradually arran<'ed in

40 '■ ■■ ■ K. MITSÜKURI. '

the median line in the form of a regular columnar epithelium from cells
forming the loose network of the primitive hypoblast. The process
proceeds from behind forward. This embryo thus closely agrees with
the first stage of Trionyx, which we described in our former
paper.

Formation of the Mesoblast.

How does the embryo described above change into one in which
the three germinal layers are completely and definitely established?
As stated in the account of the formation of the mesoblast given in
our paper on Trionyx, the process is briefly this : as the forward
continuations of the peristomal mesoblast whose commencement we
saw in the above stage, a pair of mesoblastic bands become gradually
established, one on each side of the median chorda-hypoblast, between
it and the gut-hypoblast (= Darm-Enioblast). This is the gastral
mesoblast of Rabl. From my study of CI em my s , I am now in a
position to give more exact details in regard to the first stages in the
formation of this gastral mesoblast, and as will now appear I have to
qualify somewhat my views of these earliest stages. This is necessitated
by the discovery I have made concerning the chorda-hypoblast. I find
that in Chelonia at least, only the median part of what I
have hitherto called the chorda-hypoblast gives rise to
the chorda dorsalis, and that each side of it becomes
eventually incorporated in the mesoblast. Thus, in Fig.
11, from an embryo somewhat older than that represented in Fig. 1,
the median unshaded portion alone becomes the chorda dorsalis, while
the shaded lateral parts form in the sequel part of the mesoblast.

As this is a very important point, I shall try to prove it before

FURTHER STUDIES ON THE GERMINAL LAYERS ETC. 41.

proceeding further, from observations which in my opinion make the
above conclusion inevitable.

I wish to call attention first to Fig. 23 (PJ. I\\), from the head
region of a somewhat old embryo given in Figs. 4 and 4a. Here the
gut-hypoblast (or Darm-E)itohlast), instead of juiuing the chorda-
hypoblast, turns upwards and becomes continuous with the meso-
blastic mass. The chorda-hypoblast in immediate continuation of
the chorda also turns upwards and becomes merged in the meso-
blastic mass. Between the chorda-, and gut-, hypoblast, a diver-
ticulum of the archenteron enters into the mesoblastic mass on each
side of the chorda. Now it seems to me that this section can have but
one interpretation, and represents, as clearly as we can reasonably
expect in a meroblastic egg, the process of the mesoblast development
so well known in Amphioxus. Here, however, from the outer and
upper walls of the diverticulum (I am speaking more especially of the
left side of the section), a mass of cells stretches outward. That this
mass has budded out from the walls of the diverticulum is evident
from the karyokinetic figures which we see in it. This section ought
therefore, strictly speaking, to be compared to such a section of Am-
phioxus as is given in Fig. 40 (PI. TV.), in which the mesoblast has
stretched more ventrally. To make the C(3mparison yet closer, the
gut would have to be still in open comnuuiication with the coelom
in the section of Amphioxus. Now, when the chorda, the meso-
blast and the gut-hypoblast finally separate from one another in
Clem my s , at what point does this se})aration take place ? In order
to answer this question conclusively, I have introduced Figs. 33-36
from the head region of another embryo of about the same stage.
Fig. 33 is essentially like Fig. 23. The right side of this secti(jn is
more forward than the left side and is significant, for the gut-diver-
ticulum is quite simple, and there has not yet been as much pro-

42 K. MrrstTKURT.

liferation of raesoblast cells from its walls as on tlie left side or in
Fig. 23. But the point that I want to be particularly noticed in the
section is on the left side which, as I said before, is essentially like
the corresponding' side of Fig. 23. Two sections behind this (Fig. 34),
the hypoblast has pushed towards the median line and obliterated
the gut diverticulum, of which, however, its outer and inner walls
are as yet distinguishable. Fig. 35 is two sections still further
behind, where the parts are pressed closely together. Two or three
sections yet further back, the cliorda, the gut-hypoblast, and the
mesoblast have entirely separated from one .another (Fig. 36).
This series shows conclusively that the part of the primitive
hypoblast immediately adjoining the chorda becomes
a part of the mesoblast.

Kow turn to Fig. 12 (PI. Ill), taken from the head region of the
embryo shown in Figs. 8 and da, somewhat younger than that of Fig.
4, from which Fig. 23 is taken. In this section, l)etween the chorda-
anlage and the gut-hypoblast, there is a stretch of columnar epithelium
slightly arched upwards. From the point where this epithelium joins
the gut-hypoblast, there stretches outwards a mass of mesoblast cells
between the epiblast and hypol)last. Now there can be no reasonable
doubt that this section presents substantially the same structure as the
left side of Fig. 23. If the epiblast did not press down so closely, and
if the epithelium (lightly shaded in the figure) between the points
marked with f and * arched upwards with a greater curvature, the
section would be exactly like the left side of Fig. 23. We therefore
come to the conclusion, that the epithelium (lightly shaded in Fig. 12),
stretching between the chorda- anläge and the gut-hypoblast, and con-
tinuous with both, ought to be considered as the walls of the gut-
diverticulum, and "a slight l)ay l)etween f and * as representing the
gut-diverticulum itself. Fi-om the outer walls of this diverticulum,

FURTHEK STUDIES OX THE GERMIXAL LAYERS ETC. 43

the mass of mesoblast cells (darkly shaded in the figure) are
stretching outwards. This section again reminds us of the section
of Amphioxus shown in Fig. 40.

I wish to call attention next to the embryo represented in Fig. 2.
This is interesting, because the gastral mesoblast in extending itself
forwards from the peristomal mesol^last has not yet reached the anterior
end r)f the embryonic shield, where there is as yet no head-fold, and we
are thus able to see in what manner this forward extension takes
place. Figs. 13-22 are sections of this embryo. If we look at Fig. 16
from the anterior part, we at once recognize its similarity to Fig. 12.
There is the epithelium stretching between the chorda- anläge and the
gut- hypoblast, and representing the walls of the- gut diverticulum.
From the outer end of this epithelium there stretches outwards the meso-
blastic mass (darkly shaded). We see here as well as in Fig. 12 a very
clear indication, (1) that the mesoblastic mass is divided into two
layers : the somatopleuric and the splanchnopleuric, and (2) that the
former is continuous with the above mentioned epithelium and the
latter with the gut-hypoblast. The latter fact necessitates the con-
clusion that the gut diverticulum in extending itself into the pro-
liferated mesoblast mass does so from its outer end.

When the chorda, the mesoblast, and the gut-liypoblast become
independent of one another, at what point does the separation take
place? In tracing the series backwards, wepas;s suddenly I'rom sections
hke Fig. 16 to others like Fig. 17. This point corresponds in the
ventral view (Fig. 2) probably with the place where the two converging-
depressions come together and form the single median groove. The
change is brought about by the gut-hypoblast extending itself close to
the chorda- anläge, thus shutting off the gut diverticulum from the
enteric cavity. In other words, the point marked * in Fig. 16 has
moved itself to the point marked f . In Fig. 17 the splanchnic

44 • K. MITSUKURI.

mesoblast is «till C(3ntinuoiis with the gut-by poblust. This inward
extension of the gut-hypoblast seeni8 to l)e the signal for the separa-
tion of the three structures above meritioned, for very soon we come
to sections like Fig. 18, in which the chovàn-aiilage, the mesoblast,
and the gut-hypoblast have separated from one another. From this,
it is evident that the epithelium lying between the chorda-
anlage and the gut-hypoblast (the lightly shaded part in
Fig. 16) and representing the walls of thegut-diverticu-
lum, becomes a part of the mesoblast. — the same conclusion
as was reached in the case of Fig. 23.

If we now trace the series forwards from Fig. 16 we find the
proliferated mesoblast mass (darkly shaded in the figures) growing
smaller and smaller (Figs. 15 and 14). A few sections forward, we
come to the appearances depicted in Fig. 13. In this, we find laterally
the gut-hypoblast consisting more or less clearly of a single layer of
columnar cells. As we advance towards the median line, this epithe-
lium suddenly stops at some distance from the chovdu^-anlage, and
between it and the latter structure ^ve find a stretch of epithelium
with more than one layer of cells. This part I have shaded lightly in
the figure. The increase of cell-strata in this part is possibly due to
the fact that cells here are dividing rapidly to give rise to the meso-
blast mass. The darkly shaded part (the proliferated mesoblast cells)
in this figure ought therefore perliaps to have been extended further
inwards.

P\n'ther forwards, the chorda-((///r/^t', the mesoblast, and the gut-
liypoblast are all as yet unditferentiatcd, and the loAver layer consists
of a single layer of columnar cells throughout.

It is evident from the foregoing description, that the lightly
shaded part of Fig. 13 is equivalent to the similarly shaded part of
Figs. 16 and 12, which in its turn is comparable to the walls of the

FURTHER STUDIES UN THE (TERMINAL LAYERS ETC. 45

gut-diverticiilum in Fig. 2o, and th:it this part becomes eventually in-
corporated in the mesoblast. This obliges us to come to the conclu-
sion that the median part of Figs. 9 and 11, wliich shows a regular
epithelial arrangement — the part wliicii T liavc; hitherto called the
chor(hi-]iypol)]ast — does not give rise to tiu; chorda alone but has
potentially the elements 'of the mesoblast in it. I have tried to show
what I mean by shading in Fig. 11. The media. n unshaded part is
the part tliat gives rise to the chorda ; the lightly shaded stretch, im-
mediately adjacent to it on eacli side, which corresponds to the
similarly shaded part of Figs. 13-17, gives rise to the gastral meso-
blast and becomes finally incorporated in the mesoblast. The section
represented in Fig. 11 is therefore strictly comparalile to the well-
known section of Amphioxus reproduced in Fig. o9. According
to this view, the apparently insignificant features : the bulging down-
wards of the chorda-a/î/a^^3, and the slight bay on each side of this
median projection receive their explanation.

I think, I have now sufficiently demonstrated the proposition I
started with, viz: In Chelonia, at least, only the median
part of what lias hitherto been called the chorda-hypo-
blast gives rise to the chorda dorsalis while the lateral
p a r t s of it b e c (3 tu e eve n t u a 1 1 y i n c o r p o r a t e d i n t li e meso-
blast.

r will now rapidly go over different stages and give a brief but
connected history of the above occurrences, as well as of those points
not yet touched upon.

I have already described in full the stage represented in Figs. 1
and la. It will be remembered that this embryo consists almost en-
tirely of two layers, except in the region behind the blastoporic passage,
where the peristomal mesoblast is beginning to form. This mesoblast

46 K. MTTSUKURI.

soon increases in bulk and spreads out behind in all directions like an
open fan. From the two edges of this fan, the formation of the gastral
mesoblast proceeds gradually forward (see Fig. 2 and its sections Figs.
13-22). It has sufficiently been sliown nbove th;it a certain stretcli of
epithelium found on each side of the chordn-anlage in enrly embryos
(like that given in Figs. 1 and la) l3ecomes eventually a portion of the
mesoblast. Only there is as yet nothing to distinguish it as such.
While the remaining part (i. e. the gut-hypoblast) of the lower layer
becomes gradually reduced to a single stratum of columnar cells, this
stretch (^f epithelium distinguishes itself by proliferating cells whicli
spread |)artlv upwards, but mostly outwards Ijetween the epiblast and
the gut-hvpoblast (the embryo given in Fig. 2 and its sections Figs.
13-22). At this stage, therefore, the internal end of the gut-hypo-
blast on each side is at a considerable distance from the chovdii-anlage,
(Figs. 12 and 16). The gut-hypo])last, hoAvever, soon extends itself
towards the chorda- anläge, shutting otf the epithelial stretch in question
from the enteric cavity (Fig. 17). This inward extension of the gut-
hypoblast is ])i'obably the cause of the grooves converging posteriorly
into the single median chorda groove seen in the surface views. Figs. 2
and Sa. Tliis movement seems also to be the signal for the se])aration
of the three structures : the Ghordii- anläge, the mesoblast, and the de-
finitive or gut-hypoblast (Fig. 18). The separation is, however, com-
plete only in the middle of the embryo, for, as we go backward and
approach the blastoporic passage, the three structures are again united
(Fig. 19 and 20). This is necessarily the case, I think, because the
posterior part of the embryo is growing in length. In Fig. 22, we
see that the yolk-plug has become very distinct. This has been
brought about by the change of shape in the dorsal opening of the
blastoporic passage. Whereas it is at first concave forwards as in
Fig. 1, it becomes later horse-shoe shaped (see Figs. 3 and 4), with

FURTHER STUDIES OX THE GERMINAL LAYERS ETC. 47

the concavity turned backwards.

Of an older embryo (Figs. 4 and 4a) with the head-fold and the
commencing amnion, a section from the head (Fig. 23) has already been
sufficiently described. As we pass l^nckward, we see that the cavity of the
giit-diverticuhim is obliterated (Fig, 24). A little further behind, three
structures ; the chovda-anlage, the niesoblast, and the gut or definitive
hypoblast become separated after the manner shown in Figs. 83-86.
We then obtain a section such as Fig. 25. In the middle region of the
body, the formation of the cliorda dorsnli.s is completed (Figs. 26 and
2 7) exactly in tlie way described in our T r i o n y x paper (No. 1 ). Further
backwards, the definitive hypoblsist of two sides whicli is united
across in Fig. 27, separates again from each other (Fig. 28) and still
more posteriorly, the three structures nbo^e mentioned become united
once înore (Figs. 29 and 30). Figs. 31 and 32 are so ex;)ctly like
Figs. 21 and 22, or similar figures in Trionyx, that they need no
special description here.

Trionyx Japonicus. Schiegei

After making (jut the earlier phases in the formation of the gastral
mesoblast in Clemmys, I thought it necessary to reexamine Trio-
n y X. I succeeded in finding two embryos in which the gastral mesoblast
had not yet reached the anterior end and was in process of formation.
After cutting them into sections, I fjund that they ])resent exactlv the
same structures as the Clem my s embryo given in F'ig. 2. In order to
prove this point, [ have selected and figured two sections (F'igs. 37 and
38) from one uf the embryos. In Fig, 87, tlie gut-hypoblast is at
some distance from the median line, and there is a stretch of epithelium
between it and the (.'hovd-d-aJilage, which is continuous externalJv with
the proliferated mesoblast mass. Several sections behind, in F^ig. S8,
the gut-hypoblast has shifted its inner end to the chovdn-anlagr, and

48 K. MITSUKURT.

the aforesaid stretch (3f epithelium has been cut off from the enteric
cavity and incorporated with the mesoblast.

In ti note published in the Anatomischer Anzeiger, No. 7, 1891
I called attention to the section o-iven iri Fig. 23 of the present paper,
and Fio's. 25 and 29 of our 'f rion yx paper, and pointed out that while
both represented essentially the same structure, mesoblast cells in Trio-
n y X were budded off as separate stellate cells, while those in C 1 c i ii m y s
appenred as a more or less solid mass. I liave now to qu.alify that
statement. On referring to the original sections from which Figs. 25
and 29 of Trionyx were drawn, i find that they are very faithful re-
presentations. But in sections which I have obtained lately, I find
that the cells appear aggregated in a. loose mass, and are by no means
so separate as in Figs. 25 and 29. This difference, 1 think, is due to
difference in the fluid in wiiich they were killed. The earlier
embryos were treated with corrosive sublimate, wliile the later ones were
all ])reserved in picro-sulphuric acid. I am now inclined to tliinkt that,
Trionyx and Clemmy s are after all, not so unlike in this respect.

So far as I am aware, the facts described al)ove in regard to the
earlier phases in the formaticin of the gjistral mesoblast are now
brought out for the first time. It appears to me tliat they have
considerable significance, for they make the process of the mesoblast
formation in higher vertebrates agree with the same process in Am-
phioxus mneh more closely than we have hitherto been able to do.
These facts h;i ve also, in my opinion, an important bearing in explaining
the mesoblast formation in the chick. Fig. 100 in P>alfour's Comparative
Emhniology, A'ol. 11. is substantially the same as Fig. 17 or 38 of the
present paper. Balfour says : — " From wliat has just l)een said, it is
clear that in the region* of the embryo the mesoblast originates as two

* I. e. in front of the primitive streak.

FURTHER STUDIES ON THE GERMINAL LAYERS ETC. 49

lateral plates split off from the hypoblast, and that the notochord
originates as a median plate, siniultancously witli the mesoblast. with
which it may sometimes be at first continuous." (loc. cil. }). 157.
edition of l(S8.">j. Now suppose that the earlier phases of the meso-
blast formation in Chelonia are ^ery rapidly gone through or al-
together skipj)ed over, and the state represented in Figs. 17 and 38 is
venchaà per saltum : we shall then necessarily obtain appearances which
would make us conclude that the lateral plates of the mesoblast,
or at least the part of it immediately adjacent to the chorda, becomes
split off from thé hypoblast. My contention then is that the process
of the mesoblast formation in the chick is an extremely abbreviated
form of the ])rocess descril)ed above in Ciemniys or Trionyx . The
question naturally arises whether cells are added on to the mesoblast
from the gut-liypoblast, outside of the .tretch of epithelium represent-
ing the walls of the gut-diverticulum. I wish to leave this question
open at present : there are ap})earances which lead me to think so, but
the}' are by no means conclusive. Theoretically, there should be no
cells added outside of the gut-diverticuJum.

Science College, June, 1891.

Contributions to the Embryology of Reptilia.

(No. 1. ) I. Uu the Formation of the Germinal Layera in Chelonia. Quart. Jour.

Micr. !Sc., Vol. 27. Also reprinted in Jour. 8c. College, Tokyo,

Vol. I, pt. 3,
(No. 2.) II. On the Foetal Membranes of Chelonia. Jour. tSc. College, Tokyo.

Vol. IV., pt. 1,

50 k. MITSUKURl.

Explanation of Figures.

Plate II.

Piq I — Dorsal view of a Clemiuys embryo tüken out 1 hour after its deposition.

Zeiss aa x 2. (xxxv)
Fig. la. — Ventral view of tlie same, aa x 2.

Fig. 2. — Ventral view of a Clemmys embryo 3 days old. aax2. (xxxvid.
i^'/V/. 3. — Dorsal view of a Clemmys embryo 3 days old. aax2. (xxxvii).
Fi(j. Sa. — Veulral view of the same. The head-fold marks definitely the anterior

end of the embryo, aa x 2.
B'i(j. 4. — Dorsal view of a Clemmys embryo 3 days old. aax 2. (xxxxvm).
Fir/. 4a. — Ventral view of a Clenjmys embryo 3 days old, from the same deposit as

Fig. 4. Note the two depressions, one on each side, immediately behind the

head-fold and partly covered by it. These depressions are the diverticula of

the enteric cavity seen in Fig. 23. aa x 2.

Plate III.

Fic). 5. — Longitudinal section of the Clemmys embryo represented in Figs 1 and

1« near the median ventral line. BB x "2.
Fig. 5a. — Part of Fig. 5 more highly magnified. DD x 2.

Fig. 6-10. — Selected transverse sections from a Clemmys embryo from the same
deposit aud of the same sta^e as Fig. 1. BB x 4. (xxxva).

Fig. 6. — From directly behind the dorsal opening of tlie blastoporic

passage.
Fig. 7. — Still nearer the dorsal opening of the blastoporic passage.
F'^ig. 8. — Through the blastoporic passage.

Fig. .9. — Anterior to the ventral opening of the blastoporic passage.
Fig. 10. — Through the anterior part of the embryonic shield.
F^ig. 11. — Transverse section somewhat in front of the ventral opening of the
blastoporic passage. From a Clemmys embryo a little more advanced than
Fig. 1. This is introduced to show the destiny of different parts of the lower
layer (or primitive hypoblast) : the median unshaded part becomes eventually
the notochord, the lightly shaded part on each side immediately outside the

FURTHER STUDIE8 OX THE GERMIXAL LAYERS ETC. 51

chovdii-aitlatfe gets incorporated in tlie mesoblast, and the parts external to
these sliaded portions become tlie gut or definitive hypoblast. This should l)e
compared with the section of Amphioxus reproduced in Fig. 39. BBx4.
Fig. 12. Transverse section I'lom the anterior part of tlio Clemniys embryo

■ represented in Figs. 3 and 4rt. DD x 2,
Ficjs. lS-22. Selected transverse flections from the Cloramys embryo given in
Fig. 2. DDx2.

Fi(js. IS-IH. — From the anterior part, show the manner in which the gastral
mesoblast extends itself forwards. The gut-hypoblast is at a consider-
able distance from the chorda-««/«^/,'. The lightly shaded part is the
part of the originnl primitive hypoblast that becomes incor[)orated in
the mesoblast. The darkly shaded part represents the mesoblast mass
which has been budded out from the lightly shaded part.
Fig. 17. — The gut-hypoblast has extended itself inwards to the chovA-A-anlage.
Fig. 18.— A little behind Fig. 17. The chorda, the mesoblast and the gut-
hypoblast have separated from one another.
Fig. 19. — Further behind. The three structures have again united.
Fig. 20. — Directly in front of the ventral opening of the blastoporic

passage.
Fig. 21. — Through the blastoporic passage.
Fig. 22. — Through the yolk-plug.

Plate IV.

Figs. 23-o2. — Selected tra.nsverse sections from the Clemmys embryo given in
Figs. 4 and 4«. DD x 2.

Fig. 2S. — Through the head region and the gut-diverticula. See the ventral

surface view, Fig. 4«.
Fig. 24. — Tliird section behind.
Figs. 25-28. — From the middle region of the body, showing the formation of

the notochord.
Figs. 29 é SO. — In front of the ventral opening of the blastoporic passage

The c\\oxài\- anläge, the mesoblast, and the gut-hypoblast have again

united with one another.
Fig. 31. — Through the blastoporic passage.

52 K. MITSUKURI.

Fhj. 32. — Directly beliiiul the dosai openiug of the blastoporic passage.

Figs. 83-36. — Selected transverse sections from the anterior part of a Clenimys

embryo very similar to Fig. 4 aiid from the same deposit. Introduced to

show the manner of separation of the three structures : the notochord, the

mesoblast and the gut-hypoblast. Fig. 33, BB x 4, Figs. 84-3G, DD x 2,

(XXXXVIU).

Fig. 5-5.— Through the head-fold.

Fig. 34. — Second section behind.

Fig, 35. — Second section behind.

Fig. 36. — Fifth section behind.
Figs. 37-38. — Two transverse sections from a Trionyx embryo IY2 days old.
DDx2. (127).

Fig. 37. — Is more forward. The gut-hypoblast is at some distance from
the c\\oxi\\x-anlage and the median line.

Fig. 38. — The gut-hypoblast has extended itself inwards to the chorda-rt/j/rt^re.
Figs. 39-40. — Sections of Amphioxus. From Hatschek, after Hertwig.

On the Development of Limulus Longispina.

By
Kamakichi Kishinouye, Rigakushi,

Science College, Imperial University.

With Plates V— XT.

After working out a general outline of the development of spiders,*
I undertook the study of the development of tlie Limuhis of this
country with the object of ascertaining, if possible, liow it is related to
the Arachnida. In order to collect materials for this investio-ation,
I was enabled, by Ü\e liberality of the University authorities, to visit
Ajino in the province of Bizen, in the summer of 1889, and again in
the same season of 1890. In that place, I liad exceptional opportunities
of collecting and ol^serving the eggs oîLinmhi^, by the kind assistance
of Mr. 1^). jSTozaki ;ind i\Ir. T. IsTozaki to whom my best thanks are due.

Limulus longispina is generally known hy the name of Icahuto-
gani. but there are many local names such as uniiAongame, mangoyei,
hachigani, iinkgü. etc. In I'ronn's " Die Classen und Ordnungen des
Thierreichs " we find it stated that the Chinese call their Limuhis as
Umi-dugame ov UnJdie ; but this is ' evidently a mistake, these terms
l3eing a corruption of the Japanese names, umid>ugamti and uitkgü.

* Kisliiuonye — On the Development of Areineina. This Journal, vol. IV. Part I.

54 X. KTRHIXOUYE.

Of the spawning of the American Limulus there is a minute
description hy Lockwood in the American Naturalist vol. IV ; but as
the spawnirig process of the Ja])ariese TAumJiis differs a little from
thai of tlie American species, I shall give a brief account of it.

The kahiitogani deposits its eggs chiefly in August. On calm
nif'hts durino' that month, males and females, the former on the
abdominal shield of the latter, come in with the rising tide towards
sandy sliores. Judging from appearances after deposition, the
process of spawning is as follov.'s : Egg-laying takes place between
the tide-marks, l)ut only as tliis space becomes covered with water.
The female excavates a hole, about 15 c.m. deep, and deposits eggä
in it, while the male fertilizes them. The female afterwards buries
them and begins to excavate the next hole. This process is repeated
niany times.

As Limulus can not dig deeper than about 15 cm. when the dia-
meter of the hole is less than the breadth (jf the céphalothorax, the
eggs deposited in such holes are liable to be washed out of the sand,
and carried away by waves, when the wind is rather strong. This is
especially the case with older eggs the vicarious cliorion of which
beinof inflated acts as a sort of float.

As a general thing, fishermen do not pay much attention to the
lahutogani on acc<3unt of its small economic value, and even an ex-
perienced fisherman does not know tlie place where it spawns. Such
being the case, Mr. T. Xozaki kindly detailed a fislierman to make
special search for the lahuto(jaui\'< eggs along the shores of the Inland
Sea. The fisherman succeeded in finding spawn of the animal on
the shore at Obatake, a village not far from Ajino. I was taken by
the fisherman and Mr. Xozaki to this spot. When we reached the
place, the fisherman began to dig at random those parts of the shore,
from which the tide had retired.

ox THE DEVELOPMENT OF LIMULUS LOXGISPINA. 55

While I was looking about, my attention was caught by peculiar
markings on the shore, such as are represented in tig. 1. On a close
examination these markings proved to be the tracks of the spawning
kahutogani. They consisted of a number of small roundish elevations
(about 35 cm. in diameter) stretching in a line, which is always per-
pendicular to the coast-line and never p;u-allel with it. The length of
tlie line is l|-4 m.

The elevations are highest at one extremity and become gradually
lower towards the other. The higher end is the spot where the kahuto-
gani began egg-laying. Xear the end of spawning, the legs of the
female animal are no doubt tired, so that she cannot cover en'ji's with as
much sand as at the beginning of the operation. Tlie lower end of
tlie spawn is often lost in scratches from legs, which sIkjw that tlie
direction of movement has been from the higher to the lower end.
The higher end may be either near to or away from the shore. From
this fact we may conclude that the hahatogani in depositing eggs
proceeds either towards <jr away from the shore. Tiie latter will pro-
b;ibly l)e the case when the spawning begins at the time of tlie reced-
ing tide, and the former when it begins at the time of the rising tide.

Under each elevation of the spawn there are about one thousand
eggs aggregated and compressed together into a mass. Tlie mass of
eggs is not phiced just under the centre of each elevation, but is
deposited eitlier to the left or t») the right side of tlie median line of
the whole spawn. On digging out one whole series of a spawn, I
observed that in the hif^her half of it the ef;-o--mass deviated towards

O Co

the left side, and in the lower half towards the riglit side. I'^-um
tin's I coMchided that in this case the kahutogani deposited the eggs of
tlu' Icii o\ary first, and then tliosc of the right ovary.

As eggs are easily washed (jut by waves, it is very difticult to
obtain them in their later stages. E\en when not washed out, the

56 K. KISHIXOUYE.

peculiar and \kivy convenient marks of the .spawn are lost after three or
four days. Therefore I fonnd it necessary to dig out eggs as soon as
possible after the time of deposition and to transfer them into a large
wooden box, especially made for this purpose. The box was filled
with sand and was placed at the mouth of a canal. The place was
happily chosen as the box was covered by water during high tide and
exposed to the air during low tide, and was always exposed to the sun-
shine in the day-time.

In the summer of 1889 I buried eggs of different stages in the
box ; but in the year following I buried only two series of spawns
which were deposited on the same day, and thus I could easily find
out how many days old my eggs were.

Eggs one or two days old are not spherical but polyhedral by
mutual pressure. At this time they are connected together by the
coao'ulation of a fluid with wliich thev were covered, when deposited.
The averaa'e diameter of an eo'ii' is ^t^ mm. Its volk is vellowish and
glutinous ; but when exposed to the air it soon loses water and changes
its color to dirty green, and becomes hard, and brittle. It is covered
with a thick, tough chorion which with the abundant yolk makes
observations either from the surface or by section very troublesome.

Eo-o's were fixed bv heatino- in water to 60°-70° C, or bv
])]unging into liot water of the same degree. After cooling they were
tvaiisierred into 70 7o 'dcohol, in which they were left one or two days,
'llien in the case of eggs of early stages some of them were pierced
through into the yolk with the point of a fine needle at two or three
spots, care being taken not to hurt the germinal disc. These perforated
eggs were left in 70 % alcohol for one or two days more, and afterwards
were dehydrated in ascending: o'rades of alcohol. The chorion is
si)lit naturallv or h\ heating;' and is easilv removed: but at these staoes
the vicarious chorion is formed. This mcmbrsine was perforated

ox THE DEVELOPMENT OP LIMULUS LONGISPINA. 57

before heating by applying the points of two fine needles from opposite
points at the same time.

For the surface- view of the embryo, the ventral plate was peeled
OÏÏ from the underlying yolk of the preserved egg, and was stained
with borax carmine, then washed in acidulated alcohol, and after de-
hydration and clarification was imbedded in Canada-balsam.

For the sections the eggs were stained with borax carmine or
haematoxylin in tofo. As the yolk is very abundant, the sectioning
was very troublesome. In the case of the early stages in which the
dorsal part consists only of the one- cell layered epiblast, I cut away
this part as much as possible. By using the celloidin-parafiin
method of imbedding I obtained very good sections.

I am sorry that I couJd not observe thoroughly the whole
developmental history of the Aty 6 »%(YW?', for want of sections of eo-os

Co

of very early and of very late stages. My observations were made
chictly on the stages from the formation of the germinal layers to
about two weeks before hatchino-.

External Changes.

On July 29th, 1890, 1 dug out two series of the spawn, whidi
liad been laid on the morning ol the same day, traiisfcrred them into
the box before mentioned, and examined and preserved eo-os froni
them every day.

On August 2nd (5 days after spawning), I saw many irregular
furrows on oriC pole of the egg (fig. 2). This was the first surface
change I observed. These furrows were observed by Osborn'^ in the
American Li und us.

\) Oshovu—}rrlumorphusi.< of I.imiilti.^ poli/phnnu.^. Johns llopkin's Tniv. Circ. vol. 'S'. 18Sr>.

b8

K. KISHIXOUYË.

Uli AugLi.st 7tli (10 clciy.s after .spawniiig), I found a t<iiia]l i-ouikI
whitish disc (û^. o). This UTadiiallv erdai-fi-ed and on Auo-yst 10th
(13 diiys after spawning) it had assumed an o^'aJ shape. The Linger
axis of the disc corresponds to the future median hue of the embryo,
and the disc itself is the rudiment of the ventral [)late. The disc had
divided into two unequal parts by a transverse line (fig. 4). The
smaller portion of the disc corresponds to the cephalic lobe and the
first appendage-])earing segment. Xew segments are successively cut
off from the anterior end of the larger, posterior portion.

On the morning of August 11th (14 days after spawning), three
transverse lines and a median longitudinal line were visible (fig. 5).
The median line did not extend posteriorly beyond the third trans-
verse line. Thus at this stage the central plate is divided into four
segments, three anteri<jr ones of which are divided into two lateral
halves by the median longitudinal line. About noon of the same day
one more segment had been added (fig. 6), and the median line had
l)een produced to the posterior end of the new segment.

On August 12th (15 days after spawning), five transverse lines
were seen, and the median line was produced beyond the penult seg-
ment (fig. 7). Although the change is \ery gradual, yet when we
compare the two ventral plates represented in fig. 5 and fig. 7, we
find tliat the ventral plate is much larger in fig. 7. Moreover while
the angle made by tlie lateral hahes of a segment with the median
line is almost a ri^'ht an<jle in fii!'. 5 and in the anterior region of fio-,
6, the ano'le has become acute in fiüf. 7 — the acuteness increasing' more
and more towards the posterior end.

On August 13th (16 ditys after spawning), many imporfant
changes htid occurred. The external ends of the segments had united
with each other forming a white maroiiuil band on eacli side of the

ON TlIK l)i:\ E1.«)L'MK.N'J' < )F LLMtJLUS LOMilSPIXA. 59

ventral plate (figs. 8, 9. mar. hd.). Packard'' describes the band accu-.
rately. He sa^^s : " Around the edge (of the ' primitive disk ') is a pale
areola, destined to 1)e tlie lower edge of the carapace ; it is most distinct
along the middle, merging imperceptibly into the anierior and posterior
piid of the disk, tt is a thin ridge, due to a local heaping up of cells."'
Almost simultaneously wirb tlie appenrance of tlie Tiiai-ginal bands, two
]»:ii]'ed longitudinal grooves ore formed jnst internal to the band and
parallel with the median line of the ventral plate. 1 shall call the
outer of these longitudinal grooves the first, and the inner of them, the
second, lateral longitudinal groove (figs. 8 ik 9, 1 lat. gr., 2 Jat. (jr.).
The first appendage-bearing segmeiit had become cut ofi' ïvom the
cephalic lobe. /./'., the fir-t segment of the earlier stages (fig>. 4 Ä 7)
had thus been di\ ided into tlie first appendage-bearing segment and
tlie cephalic lobe. The cephahc lobe which was earlier clearlv divided
into two lateral halves had now begun gradually to unite (fig. 8), and
in fig. 9 is seen completely united, no dark line being found in tlie
median part of it. The sixth appendage-bearing segment had become
cut off. Tbe median line had heeM mucli produced and almost
reached the posterior end of tlie ventral plate. fhe posterior part
of the line is grooved.

On August 14th (17 days after spawning), the stomodaeum (^st.)
was distinctly seen in the cephalic lobe, at the anterior end of the Ion o-i-
tutlinal median h'ne (fig. 10). It is a very shallow, roundish de]»r('s-
sion. liudiments of the distal end of the appendages had now become
distinct as round protuberances witliin the marginal IvumI and were
very conspicaious feafiu-es of the ventral pla(<^ In the marginal band
and external to the fourth a])pendage; paired, round protuberances (/a/.
li.) appear. They are a litrle larger than tlie rudiments of appendages.
As the function as well ;is homology of these peculiar protuberances

2) Packard — The Development of Limulu!: pohjphemus. Mem. Bost. Soc. Nat. Hist. vol. II.

60 X. KTSPIIXOUYE.

are uncertain I .shall call them tlie lafevid humps. The second lateral
longitudinal grooves had now reached the posterior end of the fifth
appendage- hearing segment. The seventli appendage-bearing segment
had been newly cut off. At this time all tlie appendages are post-oral.

The external changes that occur before the appearance of the
rudiments of all tlie ambulatory appendages are very hard to observe,
as the \'entral plate is small and pale at this time. I could not observe
them in the summer of 1889, except the irregitlar fissures found in a
very early stage.

As the result of the gradual enlarging of the veritral plate, the
ego^ gradnall}^ flattens on the ventral side, thus producing a space
filled with a clear fluid between the ventral ])late and the vicarious
chorion whicli is by this time already present. The vicarious chorion
dilates greatly while tlie clKirion outside it cannot expand ecjually ;
thus the chorion is necessarily ruptured. T^wo specimens of the
Ijroken chorion are represented in fig. 11. The lines of rupture are
seen to o'O round the chorion irreo'ularlv and do not form closed
circles.

On August 15tli (18 days after fertilization), the eightli appendage-
bearing segment had appeared. The second lateral longitudinal
groove had reached the posterior end of the sixth appendage-beaTing
seo-ment, bevond which the o-voove never elono-ates. The seventh
appendage had appeared on this dav.

On August 16th (19 days after fertilization), the nintii append-
age-bearing segment had appeared (fig. 12). The eighth appendage
had been produced. The median longitudinal groove, whicli had
appeared four days before in the posterior part of the ventral plate, had
become very distinct in the List undifferentiated segment. The lateral
humps were not as elevated as before.

On August 17th (20 days after fertilization), the tenth appendage-

ox THE DEYELOPMEXT OF LIMULUS LOXGISPIXA. 61

bearing segment had appeared (cf. fig. IS J. The ninth appendage had
been produced. The second, third, fourth, and fifth appendages had
become chelate. The rudiment of the flabeJlum was found as a small
round prominence on the outside of the sixth appendage. A siüiüar
])rominence was also found in the segment of the fiftli appendage,
Tlie nervous system w'as seen as indistinct, wliite, longitudinal hands
near the median line. In the Ijrain, paired inva_oinati(Mis were f )und.
The marginal band had moved much farther outward, so that the
outei- h'tcral longitudinal groo\e had become very wide and shallow.
The first appendage was found at the level of the stomodteum.

On August 18th (21 days after fertilization), mesoblastic dissepi-
ments were found, and the homodynamous organ to the flabellum was
seen in the segments of the fourth, third, and sec<jnd appendages
(fig. 13).

From August 19th onwards, the abdomen became gradually pro-
minent by the development and addition of new segments. The
hatclied embryo has ten abdominal segments. Tliis number corres-
ponds to the number found in the adult animal. The sixth and the
first appendages became chelate. The seventh appendage gradually
degenerated from the distal end, and at last a small proxinud portion
only remained as tlie metastomum. As the ventral plate increased its
surface \ery rapidly, the at first spherical egg became fiat dorso-
ventrally, and the egg assumed the trilobite-like shape (fig. 17).
The lateral hunij) separated grtidually from the marginal ])and and
w^as found in the trilobite stage «ju the (bjrsal side of the eml)rvo.

Internal Changes.

A section cut through the wliite disc found in the embryo (fig. o)
of August 7th is represented in fig. 21. It shows that in the disc cells

62 K. KISHINOUYE.

are much smaller and more crowded than in other parts of the egg.
Thus the white disc is nothin«- more than a blastodermic thickenine:.
This blastodermic thickening is not produced by the addition of cells
from within, but by the rapid cell-division in a certain space of the
surface. The cells forming other parts of the egg, both superficial and
internal, are large, spherical, and all of about the same size. At this
stage all the cells contain yolk granules w^hich are smaller in the
vicinity of the nucleus.

On August 8th (11 dnys after fertilization), the iDlastodermic
thickening had become larger and also deeper (fig. 22), but on the
next day it had increased onl}' in the horizontal plane. At about this
stage a thin transparent membrane, the vicarious chorion, is secreted
from the blastodermic cells. As the blastoderm-cells become pressed
together, and in consequence, polygonal grooves are formed around
each cell, the vicarious chorion is tucked in to fit these grooves and
presents polygonal markings with a double contour.

On August loth (13 days after fertilization), an important change
had taken place. The cells forming the blastodermic thickening had
separated into two layers (tig. 24). The upper layer is composed of a
layer of cohunnar cells and represents the epiblast, the lower layer is
many cells thick and represents the mesoblast. Thus the blastodermic
thickening gives rise to the epiblast and mesoblast of the ventral plate.
The remaining germinal layer, the hypoblast is represented by the
large yolk-cells in the interior of the egg. Outside the ventral plate,
the epiblast rests directly on the hypoblast, the mesoblast being not
yet found in these parts. The epiblast cells throughout are smaller
than the hypoblast cells. Every cell of the egg had at this stage a
distinct nucleolus. Lute, on this day, the epiblast of the ventrum had
become composed of cells in many irregular rows, as a consequence
of rapid cell-proliferation (fig. 23).

ox THE DEVELOPMENT OF LIMULUS T-OXGISPIXA. 63

On August lltli (14 clays after fertilization, cf. fig. 5), the meso-
blast layer had divided into two lateral bands (fig. 25). Since the
preceding day the mesoblast had already divided into as many trans-
verse bands as there are segments externally seen.

Late on August 12th (15 days after fertilization, cf. fig. 7 J, the
mesoblast of the fifth appendage-bearing segment had split into two
layers, somatopleur and splanchnopleur, producing a cavity — the
coelomic cavity — between them (fig. 26). As the mesoblast is divided
into two lateral hahes the cavity is of course paired. The fifth
appendage-bearing segment was well developed, and was sepai'ated
from t*lie fourth and sixth a])pendage-bearing segments by deep
grooves.

On August 13th (16 days after fertilization, cf. figs, 8 & 9). a
short median groove had formed in the posterior part of the ventral
plate. Cells underlying the groove had become loose, wandered in, and
expanded into a sheet between the epi blast and the yolk-hypoblast
(fig. 27). I shall call the groove the primitii'c streak. The epiblast
cells of the ventral plate and most of the mesoblast cells have bv this
time lost their nucleolus, while the epiblast cells of the dorsum and
hypoblast cells liave still distinct nucleoli (fig. 41). The mesoblast
of the sixth appendage- bearing segment had split into two layers,
producing the cœlomic cavity.

On August 14th (17 days after fertilization, cf. fig. 10), a pair of
the coelomic cavities, common to the cephalic lobe and the first
appendage- bearing segment, had appeared (figs. 29, 30), and another
pair in the seventh appendage-bearing segment (fig. 31). The pri-
mitive streak had receded partly towards the posterior end of the ventral
plate. The mesoblast produced from the primitive streak had separated
into two lateral halves and then divided into many transverse seg-
ments. I am inclined to believe that the mesoblast belonging to the

64 'K. KISHINOUTE.

region of the body posterior to the sixth segment (exclusive) is formed
from the primitive streak. The white marginal liand (figs. 8 & 9)
externally observed on the preceding day was a thickening of the
epiblast (lat. hd.) as represented in fig. 30.

The lateral hnmp consisted of very high colvimnar cells forming
a little protuberance (fig. 42). The -cells stain faintly.'. The lateral
hump is a ])roblematic organ which was formerly erroneously des-
cribed bv Kingsley^^ as the rudiment of the lateral eye. It was
homologised to the so-called " dorsal organ" of other Arthropods
by Watase.^' Kecently Patten'' and Kingsley'^ have described it as
serially homologous with the lateral eyes. I can not corrol)orate the
last two authors, as I could not find such a peculiar organ in other
segments, and because it a])pears at first as a protuberance and not as
an invagination wliich it should be, if it were homologous to the eye.

The yolk granules in the cells of the ventral plate had mostly
disappeared. Late on this düy the nervous system had become
marked off from the general epiblast l)y a peculiar grouping of cells
(fig. 46). The arrangement of cells in the nervous system is just like
that found in tlie retina of the compound eye for the ommatidium.
Conical shaped groups of cells with spherical luiclei are surrounded liy
compressed and slender cells with long and deeply staining nuclei.
The top of tlie cones is directed exteriorly. The brain and the ventral
nerve-'MDrds are formed at the same time, ;ind are connected with eacli
other, though their two later.! I halves are formed independently
(figs. 28-30).

On August 15th (18 days after fertilization), the cœlomic cavities

3) Kiugsluy— V(i/c.s on the Emhrijoluitij of IJmuJux. Quart. Journal of Micro. Sc. 1885.
4j Watase— On the Morpholoçiy of the ( 'ompouiul Eye of Arthropode. Stud, from the Biolog.
Lab. Johns Hopkin's Univ. 1890.

5) Patten— 0;( tlie Orlç/in of Vertebrates from Arachnids. Quart. Jouru. of Micro. Se. ISyO.

6) Kingsley — 0)i tlie Phyloyeny of J/tinulus. Zool. Anz. 1890.

ON THE DEVELOPMENT OF LIMULUS LONGISPINA. 65

of the eighth appendage-bearing segment had appeared. Since
the preceding' dnv an iiicoTn]>]ete s(']'»finn liad been produced in the first
common cœlomic ca\ity, se])arating the ceplialic portion from that
of the first appendage-bearing segment (fig. 80).

On Angnst 16th (19 days after fertilization), three pairs of in-
vaginations were visible in the cephalic region. One pair ^vas in the
external part of the cephalic lobe (figs. 12, 34, 59, ex. gr.). I shall
call it the external cephalic gro(3ve. It is the gro(Dve for the ganglion
of the lateral eye. Another ]3air was a small roundish depression, ex-
ternal and posterior to the first pair (figs. 12, 35, 59, lat. e.), Jt is
the invagination for the lateral eye. The third pair was also a small
roundish depression in front of the cephalic lobe near the median line
(figs. 12, 34, med. e.). It is the invagination for the median eye. The
mesoblast whicli had been divided into lateral halves had now re-
united in the cephalic region (fig. 59), and in the second (fig. 33),
third, and fourth (fig. 39) appendage-bearing segments. The ninth
pair of the cœlomic caA'ities had a})peared (fig. 32).

On August 17th (20 days after fertilization), one more pair of
the grooves had ap])eared in the internal, anterior portion of the cephalic
lobe (figs. 36, 38, int. gr.). Tlic new gr<)<)^•e is long arid crescent-
shaped. I sliall call it the inter] lal cephalic groove. It is the groove
for the brain. The tenth pair of tlie cœlomic cavities liad appeared.
The rudiment of the flabellum had appeared as a small, round protuber-
ance formed ofhigli, columnar cells (fig. 47). A similar, and undoubt-
edly homodynamous organ may be seen in the segment anterior to
the segment of the flabellum, though much smaller (figs. 13 and 48).

On August 18th (21 days after fertilization), the ventral iierve-
cord had divided into ganglia (fig. 13). The paired invaginations for
the median eye had united (figs. 13, 36, 37). A pair of ronnd pro-
tuberances, homodynamous with the flabellum, was found in the seg-

66 K. KISHINOUTE.

ments of the fourth, third, and second appendages (tig. 13). The
mesoblast belonging to the fifth and sixth appendage-bearing segments
had united in the median line.

Formation of the Germinal Layers.

No gastrula month is found in the formation of the o-ermiual
layers, but the blastodermic thickening, shown in figs. 3 and 21,
similar to i\\e primary thickening'' of the spider's 1:)]astoderm, may be
considered as a modified gastrnla mouth, though in addition to the
epiblast it gives rise only to the mesoblast, while the similar thickening
of the spider gives rise to both the mesoblast and hypoblast besides the
epiblast. lliongh T was nnable to stndy the segmentation of the egg
of Limulus, I am inclined t(^ believe that after segmentation the egg
is a solid sphere consisting of many splierical balls of similar size, each
of which contains a nnclens and abundant yolk granules in it. In
one spot of the egg's surface these balls are divided again and again
and form the l.)]astodermic thickening. Therefore we find many cells
in the interior of the egg.

In the spider all tlie segmentation nuclei come to the surface of
the eo-g, fifter segmentation is over, and form the one-cell layered
blastoderm enclosing the yolk which is free from nuclei. At one spot
of the blastoderm, cells are \evy rapidly multiplied and form the
primary thickening. Some cells forming the lower part of tht;
thickening wander in again into the yolk and form the hypoblast.

These two types in the formatic^n of the germinal layers, exem-
plified in Limulus and in tlie spider, are often found in closely related
o-roups of Arthropods, and neither of them is of rare «occurrence.
I think tliat the type of fjimulus is an abbreviation of that (jf the
sjüder. In the f :)rmer tlie liypoblast cells, instead oi coming out of the

7) Kishinouye— Oh the Development of Araneina. This Journal, vol. lY.

ON THE DEVELOPMENT OF LIMULUS LOXGISPIXA. 67

yolk and afterwards returning to it a.s in the spider, remain in it
from the time of their formation.

The epiblast iu Liniulus is derived in t\V(3 diiferent ways. The
epiblast of the ventriim arises from the superficial layer of cells of the
blastodermic thickening, separating from the lower cells, while the
epiblast of the dorsum is difl^'erentiated from the immediately under-
Iving hvpoblast cells by rapid nuiltiplication, thus forming a single
layer of columnar cells (fig. 41).

The mesoblast of Limiilus has three sources. One portion arises
from the cells forming the lower part of the blastoderm thickening.
This portion forms the mesoblast of the céphalothorax. The second
portion arises from the primiti"S'e streak. After the separation and
difi'erentiation of the cells of the blastodermic thickening into the epiblast
and mesoblast, and after the metamerism of the ventral plate has
already begun, a median longitudinal groove, the primitive streak, is
found near the posterior end of the ^'entral plate. From the bottom
of the groove many cells become loose and proliférai e vigorously
between the epiblast and hypoblast. These cells form the mesoblast
of the abdomen (probably the mesoblast of the last thoracic segment
also). The primitive streak is fomul even in an embryo about three
weeks old (fig. 32), Tt recedes gr;idually ]_)osteriorly giving rise to
paired sheets of the mesoblast. It may be compared to the secondai'v
thickening, the caudal thickening, of the spider's l)lastoderm, though
the latter is produced before the difi'erentiation of the germinal layers,
thus of course before the appearance of metamerism. The primiti^•e
streak of Limulus is probably homologous with the structure of the
same name in the Chordata. The section shown in fio-. 27 has a strik-
ing resemblance to a section across the primitive streak of a chick.
The third portion of the mesoblast arises from some yolk cells. In
later stages some yolk-cells losing the yolk granules come out of the

68 K. KISHINOUYE.

yolk und mix themselves with the mesoblast cells (figs. 40, 41, mes).
This takes place chiefly in the dor.sum. These secondary mesoblast
cells may be compared to the fat cells of the spider. I was unable
to trace the fate of these cells, but tliink that some of them probably
become blood corpuscles.

In early stages, just after the separation of the epililast and meso-
blast in the bJastoderm thickening, we find often some large cells in
the deep part of the mesoblast (fig. 24), find these gigantic cells seem
to play an active part in the multiplication of the mesoblast cells.

Mesoblast and Segments.

Tlie mesoblast after its formation extends very rapidly, chiefly
by division, which takes place mostly near the ventral median line.
The dorsal (distal) end of the mesoblastic somites is gradually pushed
towards the dorsal surface. In these parts the karyokinetic figures are
rareh' found, the cell multiplication taking place, as just stated, chiefly
by the division of cells in the ventral plate. The mesoblast cells in
the dorsal part of the second, third, and fourth appendage-bearing
segments become loose and spherical (fig. 39, 40).

I can not say whether the metamerism arises from the change in
the epiblast or from that in the mesoblast. When the metaineric
division takes place, the mesoblast of the ventral plate is divided into
transverse segments between which the epiblast is grooved.

The order of the separation of the segments is as follows ; — First
a common segment for the cephalic lobe and the first appendage-bear-
ing segment is cut off as the smaller anterior part of the ventral plate
(fig. 4). Then from the larger posterior portion the second, third,
fourth, fifth, &c. appendage-bearing segments are successively cut off.
When the sixth appendage-bearing segment is formed, the first

ox THE DEVELOPMENT OF LIMULUS LOXGISPIXA. 6Î)

appendage-ljearing segment is ^epai-ated from the cephalic lobe. After
two or three segments are cut off. the me-ohlast of tlie ventral plate is
divided in the median line into îwo lateral hah es, bei>inninii' from the
anterior end. in early .■stages the dafk Hues in the ventral [)late.
where few ov \io me.-ohlast cells are found, show froni the exteri<jr the
divifîion of the mesohlast into transverse segments as well as into two
lateral liah es (figs. 4-7).

The mesohlast "which was separated into lateral moieties unites
again i'vnm the a.nterior end of the ventral plate. Afterwards there
is found a special compact accumulation of mesohlast cells in the
median line of the ce})halothorax above the nervous system (tigs. 51,
Ô2, 5t), t)8, cntosL). This accumulation is laterally very thick. It is
the rudiment ()f the entosternite.

About tlu'ee weeks after fertilization, tlie mesoblastic dissepiments
are f)rmed in the cei)halothora.x bv the siidvinir in of mesohlast cells
into the yolk (ß'^^. 52, 57). They are intersomitic, dividing the yolk
into as many compa.rtments as there are segments. But there is no
dissepiments Ijetween the ce[)halic lobe and the first appendage-bearing
segment, aiid the dissepiment between tlie second and third ap])endage-
beariug segments arid that between the sixth and seventh appendage-
bearing segments are short. In the abdomen the dissepiments ure not
well developed.

Céphalothorax and Abdomen.

The céphalothorax consists of the cephalic lobe and tlie succeeding
seven segments. Tt firms the greater part of the cg^^, and becomes
gradually flat by the horizontal increase of the ventral plate.

The deNelo]>meiit of" the a.lidomen takes place wvy late. At about
hie lime wlieii I he I \\ n nie. nbltir-tie plates of tlie seventh a pi ;eudage-

7Ö^ . k. Ki8UI>'0tJYE.

bearing t^egmeiit unite in the dorsal metlian line, the abdominal part
becomes ])ronnnent, as the yolk iö then forced into it and as the
epil;)la8t and niesohlast iiicreasing by rapid cell-division produce a pro-
jection (tigs. 15. 16). Tluis the abdomen comes to be distinguished
from the cephalotliorax. The y(jlk always ]-)lays a passive part.

The peculiîiiity of the abdomen is that the yolk is found in the
later stages in the middle portion (rachis) only (figs. 54, 55), while
the cephaloth(3rax is entirely filled up with the yolk. In the abdomen
the epiblast with the enclosed mesoblast extends as two large wings (pi.)
on either side. In these wings there is no yolk. The coelom is also
not found in these wings.

The appendages borne on the abdomen ditler greatly from those
on the ccplialothorax, remaining to the last as fiat, band-like ju'omi-
nences, compressed antero-posteriorly, and the two lateral members
afterwards iiiiiting more or less at the ventral median line (fig. 55).

A Mille before hatchini«- the abdomen consists of ten se^-ments,
(tlic number e<ptal to tluit found in tlie adult animal) the four
anterior ones of wliich bear the appendages (fig. 56).

Appendages.

The fir^t rudiments of tlie appeiid.'iges a]>]tear in the stage oi' fig. 7.
J I is not righi to <"onsider the roiiiid jiroi iiberances foiuid in figs. 8, 9,
1(1. as the first rudiments of jqipendages, and the bases of the ])rotuber-
ances as the external extremities of tlie segments. A groove is produced
between every two segments. It is deeper towards the lateral ends.
Thus a [>air (,)f band-like prominences may l)e found in e\"ery segment.
Such a prominence is the rudiment ol' an a])pendage. When the
a!»iKMida<'>-e is tlius far formed, a i:'roove. the first lateral otoovc,
appears at the lateral i'd'^c <»f tlie segment on eaeh side (figs. 8, 9. 10.

<.»N' TUK i)i;\'i:L<:)i'.\ii;.\'r of i.i.miias i,().\»;isi'i.\ v. <1

1 hit, gr.). Shortly after thi.<, a second latenil e'roove is formed,
parallel and itiJernal to tlie tirst l:it(vral irt'oove (figs. 8, 0, 3 lat. gr.).
Thus in sonic segments arixc round pnjtiihei-ances l)ounded 1)v the
lateral grooNes and transverse grooNos. These protu])erances are the
rudiments of flic (Ji<;taJ portion of the ap[>endaù-es. The coihlast is wcw
tucked in from the external side of the protu Iterances, thus se[)aratin"'
the hand-like portion internal to the protuheranee.s from the o-cneral
surface of the subjacent body (fio-. 33). The banddike portions thus
cut off are the rudiments of tlie proximal [)ortions of the append-
ages. Three distal joints (f )ur in the last ambula.tory leg) are de\('lop-
ed from the [»rotuberanees. and tlu'cc [)roxinial joints t'nun the flat
ba nd-li ke j x^rt i on s.

Though the appendages (especially the anterior six p;urs) appear
almost simultaneously, yet by a close examinati«^n I f )und that the
fifth appendage a))pears first, and gradually firward; thefoiu'th, third,
second, and first appendages are formed ; then gradually backwards
the sixth, seventh, eighth, &e. appendages. The riKJiments of all the
appendages are almost alike. The order of the difi^^^vntiatit^n of the
distal [>ortion (round protuberances) of the appendages does not coin-
cide with the order of tlie appe:u'ance of the ap[)end;iges themselves.
The differentiation liegins at first in the fourth appendage, and ju'o-
ceeds in others successively to the first appendage, then graduallv
in the opposite direction in the fift'n and sixth appendages. From the
seventh appendage (inclusive) posteriorly, the second lateral rn-oove
is not formed. Thus all the abd«^minal appendages develop from
tlie banddike ])rominence-; and finally assume a leaf-like forîn.

The six anterior appendages become afterwards chelate. The first
appendage does not develop as vigorously as tlie others, ft remains
small and slender and is afterwards placed l)efbre rhe mourh and l)e-
comes the chilaria or antenna, The f dlowing five a])pendages bec(/nie

72

K, XTSTITXOUYE.

the ainlHil:itorv legs, the four anterioi- ones of whidi are, later ,six

joiiited, while llie la«t one is seven jointed. The la;^t anihnlatory leg

dilfers from the other ambulatory

leo-.s îil.r'o ])v havniij- four rod-like

a]>]'endice.s at the ij.i.se of the ^^ixtli

joint. The presence of these a{)-

pendices enable:? the last anibii-

latorv leg to serve fjr digging.

The seventh appendage gradua.lly

desfenerate.s fn /in the external side

(fig. 14), leaving a small ]>roviinal

])orlinn 'inlw ^vh!<•h he<'i)mes ihe

nieta.stonunn ol' ilie adult.

Tlic tippcndage:^ from tlie
eighth b:!ck\vai'd.-^ Ix'l.uig to ilie
al)domen. Tlie eiglrih pair of
appendage.^ bee(yme- tlie ojK'rcul um
(figs, 10, 12-14. 53-57, op.).
The riu'ht rüül left mend)ers of it

Limulus longispina. 15.
(A'eutral side).

1, Cliilaria; 7, Metasforaa ;
8, Opevcnliira.

unite secondarily wirh ea'di otlier to a great extent and f )rni a single
jtlate (fig. = - 54, 55). The proxim:d j)ortion oi" the opercnhnn coiitaiiio
the me.'ohlast cells, but Hie distal ])ortion does not. Hence the
])roxim:d poi'tion is verv mii''h tliicker than the distal ])oiiion (figs.
5.3, 54). 'I'lu' mesol)last is diffcrcntinted into muscles. Tiie Dtli-lotli
a.ppendagcs 1)ear the gilldamcllae. Among them the ninth ])air is
the earliest develojunl. fn endiryonic stages, the two lateral members
of the j)air are united a.t the median line only for a slight length (tigs.
54, 55). Like the oparcidum the a])pendage is thi«'k at the proximal
portion (^^j.;^. 49, 5.3, 57). Tlie epililast of the posterior side of the
thick portion is. invaginated by many transverse furrows. The least

ox THE L>i;\ Kl.uJ'.MEXT ol' l.l.MlUs L( »Xcilsl'lXA. 7^

iiiiniber of" the furrows whidi I observod \va^ three.- The number
increased to five, tlièn ,^ix (in the stn^-e of figs, 17. 51, 57), new
fin-rows l)einfi- added posterior to tlie older ones. Tlie einbryo, soon
nftef liatehina-, lias only four pairs of rlic abdominal ap{)enda2'es, and
the second pair alone bears the gill lamellae.

The [>e« iiliar a[)pendix, the flab.'lliim, -at. the exterior base of the
sixtVi ap|>endaL;-<î de\elops i'rom a small I'oiind protuberance (fig. 13).
The liomodynaiiKjus protuberances are also found in the segments of
t-he 2nd-5th ajipendages ; but they do not develop anv fiu-ther and
disa])pOMr.

Nervous System.

The lalcral liahc-; of the nervous system develop indepen-
dently of each other. Ividi lialf of the brain with its corresponding
ventral nerve-cord is ])roduced as a continuous long cord of epiblastic
thickening, just inside tlie base of tlie appendages (i\f^^. 12-1-1). It is
easy, howevei-, to distinguish the brain from the ventral nerve-cord.
When They aiv first formed, the former is vei-y much broader than the
latter, occnpying ahiiost rlie whole of tlie segment of the cephalic lobe,
Avhile the Neutral iierNc-ctn-d oc(ai{>ies onl\' about one tliird of the
bre:idtli of eadi a])pen(lage-beai'ing segmeiit (fig. 12).

In the stage of fig. 12 we see most distinctly that the nervous
.system consists of peculiar cell-group-; like the ommatidia of tlie eve
(figs. 34, 3G, 38. 16). These ]>eciili:!i- cell-grou])s of the nerxoiis
system were first noticed by Patten. They (lisapjK'iir Avhen the \enlral
nerve-cord is divided into ganglia and begins to ])g separated frojn the
epiblast.

A paired small invaglnatimi appears in the lateral part of thé

74 K. kishi.n'ouyï:.

brain (fig. 34 ex. gr.). The invagination is in the margin of the brain
where none of the peculiar cell-groups above referred to is f«nind.
After the appearance of this invagination there is found another jiaired
e]Ml.)lastic invagination, along the antei'ior internal corner of the l)rain
(figs. 13, 30, 38. ////. ///•.). This new invagination is also on the
maro-in of the brain, where the peculiar cell-grou])s are not found. I
believe that the external invagination is homologous with the invagi-
nation of the lateral vesicle of the spider and the internal one to tlie
semicircular groove. These cephalic invaginations of Limulus, how-
ever, are very shallow and disappear before the separation of the
nervous svstem from the epiblast takes place. They are already not
found in tlie eml)rvo in the stage of fig. 14. Ihit tlie two cell-masses
which were thus invaginated are found separate in the deep part (figs.
37, 51). The part of the brain formed l)y the external groove liecomes
the oj^tic ganglii^n of the lateral eyes as in the case (^f the spider. The
optic ganglion of tlie niedian eyes is produced from the cpildastic
thickening forming the united mouth of the invagination for tlie
median eves (fig. 69, g. uird. r. see infra). Tiie thickening is always
between, and touches on each side, the two eephalic ganglia (figs. 14,
37, 69).

At first the anteriin- and lateral borders of the lirain were directly
on the anterior and lateral borders of the ventral ])late ; but as the
oTowth of the brain la o-s l)ehind that of the ^-entral plate, it becomes
gradually se])arated from the margin of the ventral plate.

The brain whicli was almost circular in its outline, as its height
was almost equal to its breadth (figs. 12, 34), becomes afterwards
semicircular (fig. 13), later still, sic-kle-shaped (fig. 14), and shortly
before hatching almost str;iight (fig. '59). 'I'his is caused pfobal)ly by
the ])eculiar de\'elopment (if segments. All the segments seem to
develop most vigorously ai the line inidway between tlie ventral aiid

ox THE DEVELOPMENT OF LIMULU« LONGISPIXA. '^7^

dorsal median lines, i.e., all rlie seg'nients have their irreatest antero-
posterior extension on this line, and bex'onie shorter and converge, like
tlie frame -pieces of a folding fan, toAvards hoth t'lie ventral and dorsal
median lines. Therefore the external ends of the brain are pushed
anteriorly ])v the growtli (jf the succeedirjg segments. About two weeks
before the hatching of the embryo the brain proper liecomes divided
into two transverse ])ortions by a constriction (fig. 69). 'J'hiis the
brain of Jjimulus jnay be divided into four i)arts — the <'*anoliou of the
median eyes, the ganglion of the lateral eyes, and the antérieur and
posterior portions of the brain proper. 'J'hese four i)arts are arranged
in three transverse rows. 'Jlie anterior row is occupied bv tlie two
pairs of tlie <.)ptic ganglia, the middle row by the anterior ]K)rtion of
the brain pi'oper, and the posteri<jr row by the posterioi" p(»rti<jn of the
brain proper (tig. 69).

Though the posterior p(jrtion of the l)rain pi-nper is verv early
(earlier than any otlier ])art of the nervous system) cut (jif from the
e))iblast, and the iil)rous conunissure is de\ eloped between the I'ight
and lei't sitles (figs. 45, 5J, 69), its anterior ])ortion as well as the two
]>airs of tlie o])tic ganglia are for a long time not separated from the
epiblast (fig. 56).

The ventral nci've-cord consists at first of one continuous I»»noi-
tudinal thickening of the epiblast (tigs. 1:^, 30, o.")). The thickening
is at this time distinguished by the pe«;uHar cell-groups aln^adv ]neh-
tioned. At altout the stage of fig. 13, the thickening is divided into
ganglia, as the cells conij)osing it accumulate into a mass in CAery
segment. A ])air of sudi ganglia may be found in eacli of the
segments (jf the first and se\enth appendages as in the other segments.
I he ganglia of the first and tlie second a [>j)rndage-bearing segments
form the cireum(i'so])hageal ring (figs. 51 aiid 69).

Lying between tlic two laicral mcjubei-s of the L:-ani;-|ia tliere are

7'6 K. KISHINOUYE.

found .some cpihlast cells (Hg. 68, iii.c.). 'I'lies^e C'[)ib]nst cells seem to
take no part in tlie tnnnalion of tlie liiteral eomniissure. Tlicy form
probably tlie menibrane covering tlie ner^()lls system.

Cells of the nervons system, facing the centre of the egg and ly-
ino- near the mediajt line of each nervous tlrlckenino', become chaneed
into fibres. The fibi-es of the ganglia as well as those of the Ijrain and
of the o})tic ganglia of the lateral eyes commnnicate with one another
and foi-m the longitudinal commissure (fig. 51). The fibres develop
internally and form the lateral commissui-es (figs. 14, 45. 52). There
is only one lateral commissure in the bruin : — at the posterior portion
of tlie 1)rain proper (fig. 69). The lateral commissure does not de^ elop
in the segments of the first and second appendages (fig. 51). The
fibrous portion of tlie central cord develops externally and innervates
the appendages (figs. 1-1, 62, 69).

Eyes.

The lateral eyes make theii* appearance as small epiblastic
thickenino's with shalhjw invaginations, just at the margin of the
ventral plate, and at al)out the level of the posteri(jr end of the external
cephalic groove (fig^. 1^, 35, 59, 60). At this stage they are not
distinctly seen in the preser^ed eggs nor in tlie surface- view }>rej)an!-
tions. Thev are distinctly seen in sectioiis only. Ihis is due to their
verv small size and also to their being placed near the cephalic thicken-
ing of the nervous svstem and neai' the anterior end of the thick
mai'uinai band, liut in one or t\vo days alter their formation when
thev arc a little rem<ned exteriorly and posteriorly from the cephalic
thickening (fig. 13), and then from the marginal band (fig. 14), they
become easily recognisalde in the sin*face-view ]>reparations. As they
are thus removed, ilie o]»ening of their invaginations is directed
])osieri<>fl\ and dorsalh. Ilie lliickeiiiiig i> nioi-e (haii one-cell tlii(;k.

ON THE DEVELOPMENT OF LIMULUS LONGISPIXA. 77

It i.s interesting that the lateral compound eye of Liniuliis is at
first an epiblastic thickening with an invagination like a simple eye,
and not a group of thickenings or invaginations, and tliat it ap]iear.s
at the outer margin of the Lrain, as in the cnse of otlier Arthropods.
The lateral eyes of Lininlus are not thoracic eyes, hut cephalic eyes.
After their ibrmation they shift their position gradually dorsally and
posteriorly and at last they are behind the lateral hump, at tlie level of
the fourth a[)])endnge (fig. 17).

Cells forming the bottom of the invagination of the lateral eye
become large and are faintly stained ])y a colouring solution (fig. 62).
The invno-ination is faintly divided towards the posterior end into two
brariches or depressions, ventral and dorsal. The large faintly stained
cells are found in the ventral branch only. The dorsal branch is very
short and is soon aborted. The invagination of the lateral eye is not
deep, and its bottom prolonged anteriorly as a short solid tube
(tig. 63).

After the disappearance of the dorsal branch of the invagination,
cells forming the thickening, dorsal to the invagination, are pigmented
îind grouped into rudimentary ommatidia (figs. 64-66), smaller and
more pigmented cells surrounding larger and less pigmented cells.
Each of these groups of larger cells is spindle-shaped. Thus at this
time there is not to be found a separate invagination for each ommati-
dium. The first differentiation in the lateral eyes is the grouping of their
constituent cells into rudimentai-y ommatidia. I do not consider the
invao-ination for an ommatidium as of much value, as it seems to me
to be produced sec<3ndarily by the thickening of the cuticula into the
lens. The changes which take place in the lateral eyes after the for-
mation of the rudimentary ommatidia are not minutely known to me.
The optic nerve of the lateral eyes is formed from the lengthening
of cells forming the solid proLjngation of the invagination (fig. 6(!),

t8

X. KISHINOUYE.

and in tlie embryonic stnges does not communicate with the brain.
From the ndiilt anatomy and from the aua](3gy of the spider, I
consider the p(3rtion of the l)rain formed by the external groove as
tiie optic ganghon of the lateral eyes.

The lateral compound eye of Lwiulus is homologous uith the
o-roup of the lateral simple eyes of the Arachnida. For the lateral
simple eyes of the Arachnida arise as a group from a common epiblastic
thickening — as I have recently shown in the Döbutsugaku Zasshi
(the Zoological ]\lagazine, Japanese) and as is set forth in the article
immediately following in this Journal. The lateral eyes of the scorpion
are most nearly related io the lateral compound eye ol' Liiiiidus,
as they are monostichous and are placed close to one another.

The median eves a})pear as paired invaginations in paired epiblastic
thickenings near the median line and in front <)f the cephalic thicken-
inc- (fig. 12). Thev are formed just outside the brain (tigs. 34, 38),
so that they are not neural in <)rigin. The paired invaginations after-
wards aj)pro;i('h each other (tig. 13). and hnally form a median unpnired
invagination (tigs. 14, 36, 37). This unpaired invagination becomes
deep and slender and develops anteriorly and dorsally, its blind end
touching the e[)i])last (figs. 50, 56). The lumen of the invagination is
lost as it becomes exceedingly slender, and at this stage the median
eves are represented Ijy a slender solid rod (tig. 51). Later the ex-
tremity of the rod becomes enlarged and at the same time epiblastic
cells lying on it Ijecomes columnar (figs. 56, 67). The enlarged
extremity Ijecomes the retina and tlie columnar ei)ithelium forms the
vitreous body.

The mouth of the invagination is closed, when the tulje of the
invagination becomes solid. The epiblast where there was originally
the mouth of the invagination is thick and slightly depressed (figs.
6(S, 69). This thickened area of the epiblast probably gives rise

ON T?IE DEVELOPMENT OF LTMULUS LONGISPTNA. 79

to the ganglin <if tlie median e3^es, arid the slender stalk which con-
n3c|-s this are.i with the retinal portion to the optic nerve.

I was nnahle to study the later cluinges of the median eyes.
Their developineut i^'reatly l:)g's hehind that of the lateral eves. T do
not know wlictlier the anterior end of tlie retinal cells is mor|)ho]og-i-
cnlly the anterior end or not. The nn])aired retina] portion is after,
wards divided into two and gives rise to two median eyes in the adidt.
That the median eves of lAmulus are homologous with those of the
Ayachiiithi is most prol)al)le ; but it is a little doubtful whether they
are exactlv liomologous in every respect. Thus the median eye of
Limiihis ap])ears -is a tliickening anterior to the brain and outside the
semi-circii]:u' cejihalic groove, wliile llia.t of the Arachnida appears as a
thickening at tlie jiosterior end of the semi-circular cephalic groove.

I find no more eves tlian the two ])airs mentioned above, nor
unv otlier structure which I can consider as homologous with them.

Alimentary Canal.

The stomodaeum is first of all ])i'<vliiced as a shallow round
invagination in the ce]>lialic lolie (figs. 10, 20, sfoiii.). 'Hw invagi-
nation becomes gradually deej) and takes an anterior and u])\vai-d
course (figs. .50, 68). When it almost reaches the dorsum it bends a
little backwards. At first it develops with Wie surrounding mesoblast
between the epiblast and the yolk-liypol)last (fig. 50); but later, the
volk finds its wav into tlie region in front of the stomodaeum, so that
in sections, we find masses of yolk before the stouK^daeum (fig. 52,
C+l: and fif. 56). The stomoda-al wall consists of hi^-h columnar
cells (figs. 45, 68). The stomodaeum gives rise to the œsophagus
and proventriculus. As the upper lip grows posteriorly, the mouth-

80 K. KISHTXOUYE.

opening whi^li was at first pre- appendicular gradually shifts its position
backward and becomes surrounded by tlie cephalothoracic appendages.

Tlie procf-cxlaeum is not well marked out. In the sagittal section
represented in fig. 50, we see an invagination at the posterior end of
the body. The invaginatioii is crescent-shaped, as represented by tlie
horizontal section, fig. 53, and is continued to the grooves produced
by the ventral reflexion of the pleurae (pi.). Therefore the invagina-
tion can not he considered as the proctodneum.

I could not find anv trace of the mesenteron at all, even in the
embryo of the trilobite stage (fig. 17). According to l^rooks and
Bruce, the proctodaeum and the mesenteron do not appear in the
embryonic stages.

Coelom.

The early development of the cœlom may easily be understood
by examining figs. 12-17. The cœlomic cavity is produced by the
splitting u]) of the mesoblast into the somatopleur and the splancli-
nopleur. The somatopleur is thicker than the splanclmopleur, the
former being many cells thick, while the latter consists of a single
layer of cells (figs. 29-32). AVhen the cœlomic cavity is ]rro-
duced, the mesoblast is already divided into many transverse seg-
ments, in every one of which the mesoblast is separated into
lateral halves, so that the cœlomic cavities are always paired in a
seo-ment. Thouo-h the lateral halves of the mesoblast afterwards
fuse toofcther secondarily at the ventral median line, the cœlomic
cavities of both sides remain always separate. The walls of the first
cœlomic cavity fuse together along the whole line in whicli the two
lateral members meet — from ihe ventrum up to the dorsum. Fron;

ox THE DEVELOPMENT OP LTMULUi^ LOXGISPIXA. 81

the second cœlomic cavit)^ linrkwnrrls the walls of the two lateral
memliers do not fuse togetlier at the dorsal, thoiio-li tliey do at the
ventral median line.

A pair of cœlomic cavities appear in every segment, except the
segments of the second, third, and fom-tli appendages, in which the
cœlomic cavity does not appear at all. At least eleven pairs of these
cavities are pr<xlnced (fig. 53). The eleventli pair l)elongs to the
seventh ahdominal segment.

All tlie C(Te]omic cavities develoj") towards the dorsum lietween the
epihlast and tlie hypohlast, and meet witli one another at the dorsal
median line (figs. 17, 43, 44). They des elop jnst ahove the liypohlast
and do not enter nor give l:)ranclies into tlie epihlastic ontgroM^ths,
such as the appendages and the alidominal pleurae (figs. 53-55).

The first pair of cœlomic cavities is common to the cephalic lohe
and the segment of the first appendage (fig. 12). A little later this
common cœlomic cavity is partially divided into two hy an incomplete
septum lietween the cejilialic lohe and the segment of the first append-
age (figs. 12, 30); 1)ut as the cœl<imic cavity graduallv degenerates
from the jiosterior end, tlie smaller ])orti<^n helonging to the segment
of the first a])pendage disappears so(^n after its formation (i]o\ i;;).
The first Cd'lomic cavity always accompanies the stomoda3al invagina-
tion {i\g>^. 45, 50, 52). As the stomodaeum does not develop alwavs
along the external epiblast and as its disttd end takes gcadiiallv an
upward and tlien backward direction, and grows into the volk mass,
the first coelomic cavity is necessarily embedded aiming the volk (fig.
52). Taking the upward and then the backward direction the first
cœlomic cavity reaches at last tiie dorsum and tliere meets witli tlie
wall of the second cœlomic cavity, which has grown forward to this
point (fig. 17).

Tlie second cœlomic cavity bel()ngs to the segment of the fifth

82 K. KTSHTNOUYE.

appendage. It is well developed. From the segment of the fiftli
appendage backwards, a pah' of cœlomic cavities develop in every
segment. These cœlomic cavities develop at first in a dorsal and
posterior direction. The second and third cœlomic cavities are di\id-
ed into two ]iortions each — veutral and dorsal — as the cells forming
the middle ]^art of their wall become loose and fill up the cavity (figs.
14, 58). Tlie ventral portion of the second cœlomic cavity remains
as the coxal gland, while that of the third cœlomic cavity disappears
soon after its separation (fig. 14). From the fourth l)ackwards
cœlomic cavities gradually disappear from the ventrtd median portion
(fig. 55). The dorsal portion of the cœlomic cavity remains long
at the sides of the circulatory system (figs. 54-56); but it disappears
l)ef(^re the embryo hatches. The dors:d y)ortion of the second cœlomic
cavity elongates anteriorly and meets with tlie posterior end of the
first cœlomic cavity (fig. 17).

Coxal Gland.

The bi'ick-rcd gland of Packard is mesoblastic in origin, and tlie
liuuen of the gland is the remnant (^f a portion of the scond cœlomic
cavity. Tlie gland develops from the ventral p(^rti<in of the second
cœlomic caA'ity, which belongs to the segment of the fifth appendage.
Almost simultaneously with the separation of the cœlomic cavity into
the dorsal and ventral portions, (^ne laver of cells enclosing the ventral
portion is separated from the other mesoblastic cells, (which are used to
form connective tissue, muscles, entosternite, &c.,) and causes that
portion to have the shape of a sac or tube. The sac is the rudiment
of the coxal o-land. The cells forming- the wall of the o-land are

ox THE DEVELOPMENT OF LIMULUS LOXGISPIXA. 83

pressed close too-ether. I'li^y bave a high colinniiar sliape near the
ventral median line ; Itnt a« Ave recede from that liiie tliey become
almost suddenly low, fiat, and loose, and are lost in loose, scattered,
connectixe tissue cells (figs. 52, 58). This thin walled portion
becomes the funnel of the gland.

The coxal gland is at first straight and obliquely directed ; but
so<jn afterwards a small axial pcjrtion of it near the median ventral
line is bent backwards parallel to the median line makins" almost a
right angle witli tlie rest of tlie gland (fig. 14). The apex of the angle
is now gradually sliifted forward:- ; the result Ijeing that the angle be-
comes more and more acute, as the limbs of the angle increase in
length, wliile the distance l)etween their l)ases remains aluKjst
constant. The |)osterior end of the internal limb of the gland de\el<j[)s
a little downwards and then ))ackwards till it touches the p(jsteri(.)r
surface of the c<jxal joint of the fifth ap[)endage, where it is connected
with tlie epiblast and inakes the lumen of the gland communicate
freely with the exterior. The coxal gland at this stage is represented
in fig, 19. Its anterior apex reaches the mesoblastic dissepiment
l)etween the third and f jiu-th appendage-bearing segments. Its external
lindj is arched externally, the key-stone of the arch being at the meso-
blastic dissepiments between the fourth and fifth a[)pendage-bearin('-
segments. The Ihnnel is directed outwardly and posteriorly and is in
the mesoblastic dissepiment between the fifth and sixth appendage-
bearin''' seii'ments.

In the next stage (fig. 20) the anterior apex of the gland has
reached in its gr<jwth the mesoblastic dissepiments between the second
and third appendage-bearing segments, and another curvature — this
time tcjwards the mesoljlastic dissepiment between the third and fourth
appendage-bearing segments — has been added to the external limb.
A\'h('n the uland of this sta<i'e is seen from (jne side, its external

u

K. KISHIXOUYE.

limb presents many wave-like curves. The numljer of these curves
corresponds with that of the metameres in which the gland extends.
The limb presents a dorsaiJy directed curvature nt each mesoblastic
dissepiment. There is thus a dorsal as well as outward curvature
over each of these dissepiments. The coxal gland in such a stage of
development is found in an embrvo of about the stsige of fig. 17. The
further development of the gland I did not follow.

The coxal gland is probably a degenerated excretory organ, as in
development, position, and structure it is similar to the excretory
organs of other animals. It is on both sides of the entosternite (tig. 52).

The coxal o;land of Liinulus is not exactly homoloa'ous with that
of the spider. In the latter, tlie gland opens at the base of the third
appendage and reaches about to the base of the sixth appenda^i-e,
while in Linmlus the gland opens at the base of the fifth nppendage
and develops forwards to tlie base of the third ;ippendage.

Vascular System.

The chief dcn-sal circidatory vessel is formed from the mesoblastic
wall of the cœlomic cavity. As the walls of the lateral halves of
the succeeding cœlomic cavities unite gradually, beginniijg with
the posterior segments (figs. 15, 10), the dorsal circulatory vessel is
formed, pari passu, from the posterior end of the l^ody. Though the
walls of the cœlomic cavities on both sides meet in the dorsal median
line, they do not fuse together (figs. 17, 43, 44). A longitudinal and
many transverse slits separate every cœlomic cavity from its fellow
on the opposite side of the same segment, and from the preceding
and succeeding cœlomic cavities of the same side (figs. 15-17). The

ÔX THE DEVELOPMENT OF LIMULU8 LOXUISPIXA. 85

laterul hulve.s of the first cœlomie cavity only are fürfed tof>ether and
not .-separated by a longitudinal «lit (figs. 16, 52). In later stages,
however, tlie walls of all the cœlomie cavities fuse tou'ether at two
lines, d(3rsal and ventral. Thus a tulje is formed (figs. 54-5G). The
tube, as in the case of spiders, has many lateral slits (ostia). as the Avail
does riot fuse together at the intersomitic lateral places. In the tube
some wandering mesoblast cells are enclosed. They are destined to
become Ijlood corpuscles. Probably all the blood corpuscles are formed
from these cells.

As no cœlomie ca\ity is developed in the segments of the second,
third, and foiu'th appendages, tlie mesoblast of these segments plavs no
part in the formation of the wall of the d(jrsal circulatory vessel. The
first cadomic ca\ ity, ^vhich Ijelongs both to the cephalic segment and
t(j the segment of the first appendage, also does not take part in the
formation of the dorsal circulatory vessel, because the walls of its
two halves are fused together as stated above (fig. 17).

When the dorsal vessel is not yet completely formed, the aortic
arches {(10. a.) are produced at the sides of the œsophagus (figs. 17,
45). A tubular lumen appears in the mesoblastic wall of the first
cœlomie cavity, where the somatopleur and splanchnopleur unite,
between the cœLjmic cavity and the œsophagus. The lumen is paired.
The lumina of the two sides unite into one and communicate with the
lumen of the d<jrsal circulatory vessel, at the posterior end of the blind
stomodieum (fig. 17).

While the aortic arch is thus developing, a large unpaired blood
space (.s^ a.) appears Ijclow the entosternite {entost.) and around the
nerve cords ou the ventral median line (figs. 50-5:^, 56, 5(S, 68),
T'his is the sternal artery, which communicates anteriorly with the
aortic arches in later stao-es.

o

L can not but tliink that Kinu'slev is mistaken in reo'ard to the

86 K. KISHIXOÜYE.

vascular system of the American Liviuhis. niid tliat it will be found to
l)e formed in the same way as the Japanese species. The nnml)er and
position of the oslia of the American Liiiiuhis (fig. IS) agree exactly
with those of the embryo of the kdhu'ogoni [Wg. 17).

Dorsum and Venlrum.

Tlie componnd eyes of the adult Linitiliis are very peculiar in this
that tliev lie in tlie thoracic region and on the dorsal sui'face of the
céphalothorax. Previous writers differ in their opinions, as to what
thoracic segment the lateral eyes belong to, though all of them allow
that the lateral eyes are thoracic. If now the lateral eyes really belong
to a thoracic segment, it is an exceedingly interesting fact, for there is
no parallel in other animals.

AVhen we look into the matter more carefully, we are struck, first
of all, with the iiict that the lateral eyes are innervated from the brain
— a fî'.ct well known for a very long time. Xow if they really belong-
to a th<,racic segment, they ought to receive their nerves from the
o-anolia ofthat sei»inent, and it is, to say tlie least, verv peculi;ir that
tliev should be connected with the brain and not with the ganglia
of a thoracic segment.

Examining the adult animal (fig. IJ) we find that the dorsal surface
of the ceplialoihcracic shield is divided into five, while that of the
abdominal shield is divided into three longitudinal lobes, as in the
Trilobites (fig. \). These lobes I name after the corresponding lobes
of the Trilobites — the median urjpaired lobe as the g!ahcUa in the
céphalothorax, sind as the racJiis in the abdomen, the first (internal)
paired lateral lo^jes as the fixed chcclcs in the céphalothorax, and as the

ox THE DEVELOPMEXT OF LI1MULUÖ LOXGISPIXA.

Fig. IV.

Fi?. TT.— ly. Limulus lorgispina l/".

'Fig. IV. A. Transver.se secfimi ilivongli tlin
ceplmlotliorax at the level of tlie lateral
eyes. B. Transverse soctinu tlironp:]! the
alxToraen at the level of the second lateral
spine.

Flcr.Y.A Trilobite (Angelina Sedg-

Fig, V. •Wickii). A/ter Nicholson.

jileurae in the abdomen, und the seoo.id (exter.ml) p;iired lateral lobes,
which appear (3nly in the céphalothorax, as thi free cheeks (hr. eh.).

88 K. KISHIXOUYE.

Al-^o after the corresponding structure of the Trilobites, I name tlie
furrow which separates the median lol^e from, the fir.^t lateral lohe as
the axial fiuroiv. and the suture lietween the first and the second
lateral lohes as the facial suture.

It is remarkahle that in Limuhis the si^ine-!, movaljle aiid immov-
able, are found on the facial suture of the céphalothorax and tlie marü-in
of the ahd(mien, and within these boundary lines only (figs. ir-I\^).

It is also very remarkable that the eyes are f~)und below the f icial
suture oidv. The Trilobites, in which the ficial sutures of both sides
ffenerallv do not meet in the dorsal median line, have no median eves
(fig. V). Harpes among the Trilobites, and Liiniihts in which the
facial sutures of both sides meet in the dorsal median line, have the
median eye.'^.

In some Trilobites such as Mglina, the free cheeks are not well
developed ; they ara not seen from above, hence the lateral eyes are at
the lateral margin of the ce])halt)tliorax. In these forms the fixed
cheeks are al^^o very feebly deveh^ped. I regard this type, which is
found in most Arthropods as the ]")rototype of the co] »lia lotliorax.
In Phacops eic, tlie free cheeks are a little seen from the dor.^al side.
In the majoi'ity of the Trilobites the ïree cheeks are well developed at
the lateral sides of the fixed cheeks ; and in Harpes and J.liii'iln.'< they
are enormously developed, at the lateral sides as well as in fn^nt of the
fixed cheeks. In these animals the céphalothorax is mucli broader
than the abdomen.

In the ventral surface of the alxlominal sliield of Liiiiuliis we find
a region (figs. III. IV, /r.' cli.') corresponding to the free cheek of the
céphalothorax. It is an elevated portion of the lateral edge.

The development of the eyes, which I have described aljove,
shows that thev (both lateral and median eves) arise from ])ain'd
epiblastic thickenings, just at the margin of the epiblast of the ventral

ox 'J'HE DEVELOPMENT OF LTMULUS LONGISPTXA. 89

plate. The lateriil eyes;, however, gradnnlly travel fro7n the thickened
margin of tlie ventral p'ate exteriorly and posteriorly, until they are
f(innd in the d(^r>!nl surface of the embr3^o, behind the lateral hump in
the level of the f»MU-th tlK^racie appendaire. The invan-ination of the
median eye-; Ijecome.-^ o-radiially deep, and while tlie iiKjuth oï the
invagination dc.e^ not shift its ])lace, with respect to t1ie hrain, the in-
vaginated tnhe grows anteriorly arid dorsal ly, keeping its blind end al-
ways in contact with tlie epil)la.st. Its deNclopment soon surpasses that
of the thiekevied margin of the ventral plate, and at last itsti]) is found
a.t tlie dorsal surf ice <^f the emlrryo. Tn the trilobite-stage (fio-, 17)
the e{)iblast is tliickened in a line above the eves (tig. 64).

I pr<~)pose to interpret the above stated facts as follows : The
epil)last, covering the body of LimnJm may be distinguished into the
dorsum tmd ventrum, and the line in whicli thev meet is clearlv
marked out as the external margin of the pleurae in tlie :djdomen, and
as the ftcial suture (the outer inargiii of the fixed cheeks) in the
cephalotliorax. The ventrum is the epiblast wliich develops from
tlie ii])[)er layer of cells of tlie blastodermie thickening, ami the dorsum
is the descendant of the epiblastic cells covering a.ll the surface of the
ego- exeept the blastodi'rmic thickening. Thus the free-cheeks whicii
are usually looked on as a {)art of the dorsum are in mv opinion, a ])art
of tlie veiitrum. Tf we acce])t the view that the origiiial blast<i]^(^»re
is in the ventral median line of the Artln'o]ioda and tlu- stomoda^um
arid the proctoda^um are its two ends, and that the segments of the
Arthropoda are homologous with the compartments of the Cu'lenterata,
theii tlie ventrum as defined aliove. corres])onds to the subinubrella of
the medusae, all the important organs being produced ii'(-iH it a?id
the dorsum to the exumbrella. 'i'he margin of the umbrella, i.i\, tlie
boundary line between the two, has all the sense-oi-gans on it.

At the time when the eyes are first formed, the ventrum and the

90

K. KISHIXOUYE.

ventral plate are one and the same ; but later tlie ventral plate does
not keep pace in its growth with the ventrum. The ventrnni extends
very quickly, as is known from many karyokinetic figures in it, while
the dorsum seems to increase very little after its formati(^n (after tlie
differentiation from the underlying liypohlast), if it increases at
all. As the result of this increase of tlie ventrum, tlie egg is flattened
dorso-ventrally, and the ventrum is in the céphalothorax reflexed up-
wards and forms apparently a ])art (^f tlic dorsum, and in the abdomen
is elevated as in fig. IV . The retinal portion of the eye is always at the
maro-in of the ventrum, iust as tlie eves of the medusae are alwavs on
the umbrellar margin, between the exumbrclla and the subumbrella.

The maro-in of the ventrum of the cephalic lobe develops not only
dorsally but also posteriorly. Thus, though the lateral eyes are found
at the level of a thoracic a]ipendage in later stages, they are not pro-
duced there, but are formed in the cephalic lobe like the eyes of other
bilateral animals.

Table showing the chief early changes of the Kabutogani's eggs,
which were fertilized on July 29, 1890.

SEGMENT.

OŒLOM.

APPENDAGE.

br.

1

2

3

4. 5

6

7 Is

9

If

In:

1

2

3

1

5

6

7

8

9

ir

I

•>

3

i

5

6

/

8

9

Aus.

10

11

12

.1
T

X

X

X

1

X

X

13

X K

K

X

'<

K

X

<

X

14

X

X

r

K

\

15

•

X

-

.<

.<

16

K

X

X

17

X

<

_

_

„

^

„

X

ON THE DEVELOPMENT OF LIMULUS LOXUISPIXA. 91

Relation ofLimulus with Other Arthropods, with Some Remarks
on the Arthropod Ancestry oflhe Chordata.

'i'he clo.^est rcJative uf Liiindus auioi-.g tlic Arthropüda is un-
douljtedJy tlie Trilobite.s. The relations l^etweeo them have already
been g'iven in the previous section. Tlunigh the appendages and the
internal structure of the Tril(.)l)itey are but little known, their external
features match I hose of no other animal 8o well as those i)f l/hiiulus. The
five-lobed céphalothorax, the three-lobed abdomen, and the eyes under
the facial suture, are the characteristic features of both Linuilus [unl the
'I'rilobites. Tliesc characterislics are not distinctly found in other
animals, even if not entirely wanting, ^[oreover, Liiiinlns and the Trilo-
bitetj resemble each other in their haljitat — swarming in the muddy
bottom of a shallow sea.

The chief ditterences between Limnhis and the Ti'ilobites are as
follows: — In the Triloljites, some anterior abdominal segments ;»re
separate, while in Liiiiulus all the abdominal segments except the last
one are united into a single shield. In the Trilol)ites some posterior
al)dominnl segments are united and form the pygidium, while in
Liiindns the last ^-cgment is separate from all the other abdominal
aegments and forms the sword-like telson. In the Tiilobites the two
lateral lobes (jf the free cheeks are generally not uinted in the dorsal
median line, and the median eyes are generally absent*, while in
Liiiivhis the two lateral lobes of the free cheeks are united in front and
a pair of tlie median eyes is present.

Those differences ai'c not of mucli importance and do not speak
against a close relationshi[) existing between the Trilobites and Liiindus.

The next near allies of Liiitidas are the Merostomata Çlvury-

* Present in Hurpc^.

■92 K. KISHIXOUYE.

})terid((, Ptcnigolns, &t*.). Two pair^ <^f eye.s («hu', lateral and roni-
])ouii(l, the other, median and simple), the ambulatory appendages
around the mouth, and the .sworddike tel^on, are the points of re-
semblance between them, ihit tliere are msmy differences ; the chief
ones among which are the want of the facial suture in the dorsal surface
of the céphalothorax, and the fact that the a])pendage8 are divided into
ni(jre than six segments in the ^lerostomata. The Merostomata re-
semble closely tlie Scorpi(jnida, an order of the Arachnida. Hence we
find a relation between Liiiiidns and the Arachnida.

Fr()m early times the genetic relation between Limuhis and the
Arachnida has been maintained, and at present we do not doubt the
reality of such a relationship; but ^vhether Liiiudas ought to be
classified anion^' the Arachnida or amono- the Crustacea, or be made
into an independent class is still an o])en question. ]n order to show
at a glance in what points Liinuhis resembles, and in Avhat j'oints it
differs from, the Crustacea on the one hand and the Arachnida on the
other, I liave introduced the table on the next [>age. I venture to
think that there are some new j)oints which h;i\e not been noticed by
previous writers but which !ire nevertheless quite signilicant.

From the table it will be seen that Liiinilus differs in many
points from both the Crustacea and the Aracluuda. With the sole
exception of the facial suture, there is no important point in which
Llimdas diiters from Ixjth the Crustacea and the Arachnida. In those
points in wliich Liiinilus differs froni the Arachnida, it resendjles the
Crustacea, and where it ditfers from the Crustacea it resembles the
Arachnida. Tlierefore it appears to me not ad\ isable to place Ijliiiidiis
in either class, or to make it an appendix to either. On the whole it
seems safe, or rather necessary, to make an independent class for Liiituhis
a] id the Trilobita.

Hitherto the Merostomata have u'enerallv l»een consideied lo be

ox THE DEVELOPMENT OF LTMULUS LOXGTSPIN'A.

93

more nearly vehieà to LimuJun than tlie Trilohita are; but T venture to
doubt the correctness of this view : my conchisions as set forth above
point in just the opposite direction.

Lateral eyes

ARACHXTDA

many, simple

]Mediari eves

The distal portion
of the amhulatory
api^endas^e from the
carpopoclite consists
of

Yolk in the emlirvo
remains long' and
aljiindant in

Oœlomie cnTÏtv

two (paired)

four secrmonts

the posterior region
of the body

LTMULUS

riîUsTACEA

two, componnd two, compound

two (paired)

three se^-ments (in
the last pair, four)

the antei'ior rej^'ion
of the body

one pair m every
seo-ment and enters
into the appendao^o

Malpig-liian tube

Brain and optic
"rançlia ai'iso from

Xanplius sta^e

Breathe

Oric^nsof mesoderm
of the ventrnm

Blood vessel en-
sheatlies the ner-
vous system

Entosternite

present

paired grooves in
the paired epiblastio
thickening's

wantiuLC

does not enter into
tlie appendage and
is not developed in
some seo'ments.

wanting:

one (unpaired)

three segments

the anterior region
of the body

does not enter into
the appendage and
is not developed in
some segments

wanting

paired grooves in
t)ie paired epiblastic
thickenings

paii'ed epil.>lastic
thickenins's

wanting

in water

two (in spiders)

two

Facial suture

present

indistiîict

present^

present

most of them in
water

in most of them not

wanting

distinct at
drirsal 'side

the

distinct at the mar-
gin

Tlie name Gi/jaiifo>^trara may conveniently be retained for the new
and somewhat restricted class contai niuu' Limulii.'^ and the Trilobita.
The ^lerostomata excluded from the group (Miglit, in my o[)inion, to
be classified as an appendix to, (ir as an order of, the Arachnida.

94

K. KISHINOUYE.

The ofenealoofica] tree which I would construct is as follows :

Arachnida Merostomata

Crustacea

What order of 'i]\e Crustacea iy moA neai'ly related to tlie Gigant-
ostraca I do not know, sis the developmental liistory of different orders
of the class is not yet well known.

I have already compared the eyes of Limuhis with those of the
Aracluiida, and foiuid that they are probahly hi^moh^u'ous witli each
other. ])iit I do not know whether the eyes of L'lmalm are homologous
with those of the Crustacea or not.

The homology between the pulm(3nary sac of the Ai\aclinida and
the lamelligerous gills of Liinulns is most probable and is generally ac-
knowledged. l^>at as to the manner in which the former has been deriv-
ed from the latter, whether by invagination or by subsidence, o[)inions
of investigators do not agree. If a pulmonary sac of the Araclmida is
formed by the invagination of a lamelligerous appendage of a Lhnulu^-
like ancestor, (1) tlie mouth of the invagination ought to look towards
the head, (2) the gill lamellae ouglit to 1)8 formed on the posterior wall
of the invagination, (o) new lamellae ought tobe added ventral to those
already f ^rined, i.c.^ the most dorsal gill lamellae must be formed first.

ON THE DEVELOPMENT OF LIMULUS LOXGISPIXA. 9-^

But none of these points so happen in the development of the pulmonary
sac of the Arachnida. Hence I think the pidmonary e-ic of the
Arachnida has been produced by the subsidence of the lamelligerous
appendage of a Limulus-Wke ancestor.

Tlie number nnd position of the eyes are exactly the same in
Liiimhis and in tlie Choidata. The median eyes of Lhiiiihis are repre-
sented by tlie pineal eve of the C'hordata, which is pioi):!l)Jy frrmed by
the union of a pair of median eyes such as tliose in Tj'mnliis, The
lateral eyes of Liniiilns isre repre>erjted by the paired e}es in the
Chordata. The paired eyes of the Chordjit;i differ from the lateral eyes
of X(?'»«t/z(s by having- their retinal portions inverted; but this is the
effect of the closure of the medullary plate with the optic area into a
tube. The retina of tlie [)aired eyes of the C'hordata is also composed
of ommatidia — a cone surrounded by many rods.

The lateral eyes of Liimdus receive their nerves from the pre-oral
cephalic lobe. Then the ancestral mouth of the Chordata must be
searched for^behind the optic chiasma, and witliin tlie ring of the ner
vous system. We have an invagination in the nervous system, which
cannot be explained otherwise than by considering it as the degenerated
stomodai'um of the ancestor. It i-^ the infundibulum. The view that
the infundil)ulum is the remnant of the ancestral mouth is maintained
by Cunningham, l^itten, Gaskell, &c. The facts tliat the infundibulum
is closely in contact with the anterior end of the mesenteron in the
embryonic stage, and that it is behind tlie optic chiasma, fixvours
this conclusion.

The origin of the mesolilast, separation of the ner\'e-cord from the
epiblast, formation of the lieart, the number and position of the eyes,
the grooves in the Ijrain, &c., make Limuliis approach in(_)re cl(3sely to
the Chordata than it was thought to do formerly, and accordingly make
the Arthropoda more nearly related to the C'hordata than to tlie Vermes.
Tokyo, June, 19, 1891.

96

K. KIöHIXOUYE.

Explanation of Figures.

List of Abbreviations.

1, 11, III,

ao. a.

apj>.

br.

a

CO.V. (jl.

d.

d.g.

en tost.
C.V. ijr.

Jlab.
ßab'.

[I-

<j. I at. e.

tj. Died. c.

Id.

int. <jr.

lat. e.
lat. (jr. 1.

kc. Segments of the 1st, 2ucl,

3rd, i*v.c., appeudages.
Aortic artery.
Appendage.
Brain.

Cephalic lobe segment.
Coxal gland.

Dorsal side of the embryo.
Dorsal groove of the

lateral eye.
Entosternite.
External groove of the

brain.
Flabellnm.
Structure humodynamous

•with the flabellnm*
Ganglia.

Ganglia of the lateral eye.
Ganglia of the median eye'
Heart.
Internal groove of the

brain.
Lateral eye.
First lateral groove of the

ventral plate.

lat. (ir. 2.

Second lateral groove of

the ventral plate.

lat. h.

Lateral hump.

mar. bd.

Marginal band.

m. c.

Epiblastic cells between

lateral ganglia.

Died. e.

Median eye.

ijied. I.

Median line of the embryo.

mes.

Mesoblastic cells derived

from the yolk-hypoblast.

n.

Nerve.

oeso.

(Esophagus.

op.

Operculum.

ost.

Ostia of the dorsal circula-

tory vessel.

pi.

Pleura.

jiriiii. gr.

Primitive groove.

/iri)ii. ■■str.

Primitive streak.

prov.

Proventriculns.

St. a.

Sternal artery.

slum.

StomodcBum.

V.

Ventral side of the embryo.

r. g.

Ventral groove of the

lateral eye.

ox THE DEVELOPMENT OF LIMULUS LOXGISPIXA. ^7

Plate V.

Fig. 1. Peculiar markings oii the shore, showing the place where eggs were laid.
Fig. 2. Surface view of an egg which has many irregular fissures (5 days after

fertilization).
Fig. 3. Surface view of an egg with the blastodermic thickening (10 days after

fertilization).
Fig. 4. Surface view of an egg, at the beginning of the metamerism (13 days

after fertilization).
Fig. 5. Ventral surface view of an egg, 14 days after fertilization.
Fig. 0. The same as above, a little more advanced.
Fig. 7. Ventral surface view of an egg, 15 days after fertilization.
Fig. 8. Surface view of the ventral plate of an egg, at the commencement of the

appearance of appendages (16 days after fertilization).
Fig. 0. The same as above, a little more advanced.

Fig. 10. Surface view of the ventral plate of an egg, 17 days after fertilization.
Fig. 11. Two specimens of the chorion, broken up by growtli.

Plate VI.

Figs. 12-14. Three successive stages in the development of the ventral plate.

The nervous system is marked dark red, while the mesoblastic somites are

marked blue and the cavities in them light blue. Fig. 12, 19 days old ;

fig. 13, 21 days ; fig. 14, 25 days, about x 30.
Fi-'. 15. Side view of an embryo, about 24 days old.
Fig. 10. Dorsal view of an embryo, about 25 days old.
Fig. 17. Dorsal view of an embryo of the trilobite stage, showing the formation of

the dorsal circulatory system.
Fi". IB. Heart of Uiiniliis l'uhifhenuts, after A. Milne Edwards (much reduced).
Fig. I'J. Coxal gland of an embryo, about 27 days old, constructed from sections.

a. Ventral view. b. Side view.
Fig. 20. Coxal gland of an embryo, about 30 days old, constructed from sections.

a. Ventral view. b. Side view.

98 K. KISHIXOUYE.

Plate VII.

Fig. 21. Transverse section through the blastodermic thickening of an egg,

10 days old, shown in fig. 3. 2C.

Fig. 22. Transverse section througli the blastodermic thickening of an egg,

11 days old. 2B.

Fig. 23. Transverse' section through the rudimentary ventral plate of an egg,

13 days old, showing the separation of the blastodermic thickening into

epiblast and mesoblast. 2B.
Fig. 24. Portion of a section, similar as above, showing the columnar epiblast

cells and a mesoblast cell wilh 2 very large nuclei. 2D.
Fig. 25. Transverse section through the cephalic lobe of an embryo, 1-i days old

(fig. 5), showing the separation of the mesoblast into 2 lateral bands. 2B.
Fig. 26. Longitudinal section through the ventral plate of an embryo, 10 days

old (fig. 8), showing the appearance of the cœlomic cavity in the 5th

segment. 2B.
Fig. 27. Transverse section through the primitive streak of an embryo, 10 days

old (figs. 8,9), showing the formation of the mesoblast cells in the

posterior part of the ventral plate. 2D.
Figs. 28-31. Transverse sections througli the ventral plate of an embryo, 17 days

old (fig. 10). 2B.
Fi". 82. Transverse section through the posterior part of the ventral plate of an

embryo, about 20 days old (fig. 14). 2B.
Fig. 33. Transverse section of the anterior part of an embryo, shown in fig.

12. 2B.

Plate VIII.

Fi"s. 3-4, 35. Horizontal sections of the cephalic region of an embryo, shown in

fig. 12. 2C.
Figs. 36, 37. Horizontal sections of the cephalic region of an embryo, shown in

fig. 13. 2C.
Fig. 38. Horizontal section of the cephalic region of an embryo, shown in fig.

14. 2C.

ON THE DEVELOPMENT OF LTMULUS LONGISPINA. 99

Plate IX.

Fig. 39. Portion of a transverse section of an embryo at the stage of fig. 12. 2C.
Fig. 40. Portion of a transverse section of an embryo, shown in fig. 18. 2C.
Fig. 41. Dorsal portion of a transverse section of an embryo, showing the

cohimnar cells of the dorsum. 2D.
Fig. 42. Portion of a transverse section of an embryo, shown in fig. 10, showing

the prominent lateral hump. 2D.
Figs. 43, 44. Dorsal, median portions of transverse sections of an embryo, at about

the stage of fig. IG, showing the formation of the heart. 2D.
Fig. 45. Portion of a transverse section of an embryo, represented in fig. 17. 2C.
Fig. 40. Anterior portion of a longitudinal section, showing the peculiar cell

group of the brain. 2D.
Fig. 47. Portion of a transverse section of an embryo, shown in fig. 13, through

the fifth ganglia. IC.
Fig. 48. The same as above, cut throngh the sixth ganglia. IC,
Fig. 49. Longitudinal section of the second abdominal appendage, before the

formation of the gill-lamellae. 2D.

Plate X.

Fig. CO. Median longitudinal section of an embryo at the beginning of the

trilobite stage. 2ai.
Figs. 51, 52. Horizontal sections of an embryo in the same stage as above. 2aa.
Fig. 53. Horizontal section of the abdomen of an embryo of the trilobite stage.

2aa.
Figs. 54, 55. Transverse sections through the abdomen of an embryo, a little more

advanced than the one above mentioned. 2aa.
Figs. 5G, 57. Longitudinal sections of an embryo in the stage of fig. 17. 2aa.

Plate XI.

Fig. 58. Portion of a transverse section of an embryo, shown in fig. 14, through

the coxopodite of the 5th appendage. 2C.
Fig. 59. Transverse section (a little oblique) of the cephalic region of an embryo,

shown in fig. 12. 2B.
Fig, GO. Portion of a transverse section of an embryo, shown in fig. 13, through

100 K. KISHIXOUYE.

the lateral eye. 2D.
Fig. 61. Lateral portion of a transverse section of an embryo, a little before the

stage of fig. 15, through the lateral eye. 2D.
Fig, G2. Transverse section of the lateral eye of an embryo, shown in fig. 17.

2D.
Fig. G3. Two consecutive transverse sections of the anterior end of the lateral

eye. 4B.
Fig. G4. Transverse section of tlie lateral eye of an embryo of the trilobite stage.

2D.
Fig. Go.. Cross section of three ommatidia of the lateral eye of an embryo of the

trilobite stage. 2F.
Fig. GG. Longitudinal section of the same. 2F.
Fi». G7. Longitudinal section of the median eye of an embryo, at about the stage

offig. 5G. 2D.
Fio-. G8. Portion of a longitudinal section of an embryo, sliown in fig. 15. 2C.
Fic^. GO. Diagrammatic representations of tlie anterior portion of tlie nervous

system of an embryo of the tri]ol)ite stage, a. Frontal view. b. Side

view of the right half.

On the Lateral Eyes of Spiders.'

bv

K. Kishinouye, Riéakushi.

Science ('(»liege, Impérial I'liiversity, Tokyo.

In order to coiiipaiH- Lininlns and spiders with re^jpect to the
development of their eye.-. I re-exnmiiied ray sections and found that
I had ()\ci-Iooked in my reeent p;i[)er. a very imi>orhint stage in the
develo] »nient of the Jateral eyes of sjnders,* so that my views on this
])()int were in part iiicorreet. Tliis ohlio-es me to write ont hriefly the
ncnv ronchision J have arrived at.

,MI (lie lateral eves of sjnders. giaieraJiy three ]»airs, arise from a,

common thickening of the epiblast
on each side at the posterior ex-
terna] corner of the lateral vesicle
before it is completely cut off
from tlie geiieral epiblast — at
about the stage ol tlie reversi()n
of the emljrvo. Tlie thickening
is sligbrly iiiragiiuitdd and con-
sists of cells arranged in many
irregular rows (fig. A).

After the process of the re-
version of the embryo has greatly
advanced, the invagination disap-

diirsiil

^ Fig.B.

ri'iitriil

viitrnl

Lougitiiiliual sections through the
" optic area " of the lateral eyes. Fig. B
shows the "anterior lateral eye'" and
"posterior lateral eye'" only. Zeiss
2xJ).

1. This article was published in t)ie Zoologischer Anzeii,'er Xt). 370 of Nov. 2 1SÎ)].

* Oil fill- Di'i-flopiDt'iit Ol' Anuii'iii'i. This Journal. Vol. IV.

102 K. KI8HIX0UYE.

pears, niid the epiblnstic tliickeuing above the lateral \esic]e, which
latter is by this time separated from the general epibla.st becomes flat.

A\ lieu the reversion of the emljryo is almost over, a- differentia-
tion occurs among the nuclei of the epil3lastic thickening. At three
places in the thickening, luiclei become a little larger, and stain slightly
less than those which are found elsewhere, ajid wdiich are pressed
together and are of a long ellipsoidal shape (fig. 1j).

These three groups of larger nuclei form the retinal portion of
tlie three lateral eyes. They are spindle-shaped or rather wedge-
öhaped, narrower towards the exterior surface. Later tliey are separated
from the surrouiiding nuclei at the narrower end l)y a ring-like furrow,
peculiar to tlie lateral eyes, and the surrounding nuclei grow and ineet
together o\er the retinal |)ortion, forming a layer of cells — the
^itreous body.

The lateral eyes receive tlieir ncr\es from a portion of the brain,
formed ])y the lateral vesicle. Thus the latter is the optic ganglion,
formed from an invagination, independently of the semicircular
cephalic groo^'e wdiich gives rise to the brain proper.

The common epif)lastic thickening of the lateral eyes of spiders is
most probably homologous with the e]>iblastic thickening of the
lateral compound eyes oi' Liiiiuln.^, as its position is just the same :ind
the invagination is similarly produced in both cases. Then, are the
peculiar groups of larger nuclei of spiders homologous Avith the
tmimatidia of Jy///i/f///.s / 1 am inclined to believe that such is the case
and that fli<' lalrral riics of .spiders are se/Kirated, ('tilargril. au(J modified
(jmiiKttidia of a coDipinuid eye of tlie iv ancestor.

In PI. W, illustrating Parker's ])aper " 'Ilie Eyes in Scorpions,"
we distinctly see that all tlie lateral eyes of the scor])ion tilso arise from a
Ci)ninion thickening o!' tlie epiljlast. Thus we see that the occurrence of
this interesting plienomenon is not confined to spiders but is found in

ox THE LATKlîAL EYES OF SPIDEIÎS.

108

ail allied ofdei-, Scorpioiiido:!. Pai'ker, however does not «eem to
consider this interesting' fact as of much vahie, il'lie has not indeed
o^■erl^Joked it.

Lankcster and lîonrno* arriNcil at rlic same (-(ynchision as \ have
done, from a study of the strii<:ture of the eyes of the adult Liinulus
and of Scorpio: hut thev Avaiited the emhryologi(';d proof. Since
tliey Mrotc miidi work has l)een done on tln' de\ clopment of spiders,
scorpions and Lhiiiihn^ : but no one till now has coiiiii'incil their
conclusion.

The facts that the number and the relative position of the simple
eyes of s})iders and scorpions are very varialüe and that the eyes are
j)laced more closelv together in the emln-yonic tliau in latei* stages,
sj)eak in fa\oui' of oin' eonclusion.

The separation and modification of the ommatidia of a compound
eye into simple eyes ai'e ])robably the ctfects of t lie change of the
animal's liabit— from that of wandering about in pursuit of prey to
that of Iving in Avait for it.

The lateral eyes of spiders Avere called " Augen mit pr;il)a(allären
Kern " by «J raber, and '' Xebenaugen " by 15ertkau ; but -as they are
homologous ;is a whole with the lateral eyes of scorpions and with the
lateral conpound eyes nï LiiiiuJus, 1 propose to call them laU'val eijes as
\ have done in this paper.

* Lankestor :i.u<l Boiu-ue — 'ZVc Minnie Strticturc of thi' f.iifrni! 'iiul the Cfittrnl Eijeit of
Sroriiio and of Linin/iif. «.^nart. Join-. Mii'. S»;. XXIIT.

Notes on a Collection of Birds from

Tsushima.

by
Î. Ijima.

Riéakushi, Ph. D., Ri^akuhakushi,

With plate XII.

The interest attacherl to the island of Tsushima,* as one of the
Hnks connecting the Japanese Islands with the continent, led ns to
send Messrs. Namiye and Tsnchida, Assistants in tlie Zoological
! laboratory, Science College, to make a general reconnaissan^'e of its
lamia. They collected specimens at several places on the island,
altoo-ether from Febr. 19tb to April 7th, 1891, but ofthat time, short
as it was, they conld devote only a part to the work of the ornitholo-
o-ical collection. Nevertheless, they succeeded in acquiring 136 skins
of birds referable to some 48 species, a number which well attests the
zeal of the collectors. It is upon these specimens that I now propose
to make notes.

* Tsushioia lies iu tlio Straits of Corea, between Kiushiu and the Corean peninsula.
Although it had been hut imperfectly explored l)y zoologists, we had long known of the existence
there of a species of wild-cat fonnd in no other of the Japanese islands, and of a wood-pecker,
Tliriiwna.v richardsi, considered to lie peculiar to that island. The occurrence there of the
Chinese Ring-necked Pheasant, Phasiaiius toniuntu^, not found on any of the main islands of
Japan, has also been recorded, but this T I:.elieve is to be regarded as an element introduced
from Oorea 1 ly huuian agency.

106 • I. IJIMA.

1. IVÏerula fuscata, (l'ai].)

J;ip. names : Tsugnrai ; Chöiua.

This species was fcund iii gTent niimhers on open paddy-fieldH.
They vrere pro1jpJ)ly on rnioTntion. Eiirht speeimen;«!, dating Fehr.
22iid (!) ]\[nrcli 7t]i, were ol)t;!ined at four différent localities.

A specimen Avas also hiv^nght liome from the island of Tki,
between Tsnshima and Kinshiti.

•2. Merula naumanni (T.i

ifarlivo-t.sngniui : Akaüiüii.

This species, wiiich but rarely straggles to the north-eastern
portion of fIond<^, seems to be a common visitor to Tsushima. Three
si^ecimens, all inales (dating Febr. 22n^to Marcli 6tli), were ol)tained.
They were foniid mixed in flocks of the alcove species. According
to the repcn-t of Taczanowski (Troc. ZooJ. Sue., 1888, p. 463)
.1/. uanumimi sliould also Ije common in Corea dnring tlie time of
migrations.

3. Merula pallida (Gm.)

Shirohara ; Yabntsngumi.

Numerous in ])nshes. Four specimens obtained, Fefa-. 19th to
March 6tli.

4. Monlicola solitaria (Miiii)

Iso-l)i_yo(lovi.

A iemaJe and two male;- were collected at W'ani-ura at the
northern extreniiiy of ihe island.

NOTES OX A COLLECTION OF BIRDS FKOM TSUSHIMA. 107

Ö. Tarsiger cyanurus (Pa)].)

Ruribitiiki.

This lunl was very ubiindantly mei: with. Eight specimens were
()l)taiijed at Iziihara and vicinity on Fehr. 19th and 21st.

A female specimen of Puiticilla aurorca was obtained on the
island of Iki. This species undoubtedly occurs also on Tsushima.

(i. Hypsipeles amaurotis (T.)

Hiyodori.

This species was one of the commonest Inrds of the island.
Fifteen specimens obtained at cliiferent localities. In Tsushima as in
Hondo, this bird has the habit of frequenting the blossoms of Camellia
japonica. All the specimens from Tsushima have more or less pollen-
powder, undoubtedly of the above-mentioned tree, attached t(3 feathers
at the base of bill. Mr. IS'^amiye observed at Tsushima that the same
tree is a favourite resort of Mustela iiwlaiupm daring night or in early
morning. Anatomical examination of this mammal shot down from
tliat tree, in\ariably showed him no ..ohd contents in the stomach. On
the other hand, lie found that the half-open aiid up-turned corolhi of
(Jaiiidlid contains drcjps of nectar, much sought after 1)\' chihh'en.
1 share with him in the belief that the Mttstela as well as the lîrown-
eaved liulbul seeks that fluid instead of feeding on [)ollen.

On some of the specimens of llypsi petes aiitaiiratis fnjm Tsu-
shima, I notice the jugulum rather distinctly traversed by a band
of pale-chestnut joining the dark chestnut patches on the sides of tlie
liead. It is caused by the apical half of the jugular feathers being-
suffused with that colour, which gradually fades away into the whitish
of the attenuated end. The latter is usually found more or less
abraded. 'Hie band is by no means e(pially pronounced in all

108

ï. IJIMA.

specimens and, where very faint, might easily be overlooked. Bring-
inu' to"-ether Hondo specimens (obtained in winter) for comparison's
saJ^e, I find similar colouring of the jiignlar feathers ; in at least three
ont of ten specimens the jngular band is as marked as in the Tsushima
specimen which first atti'actcd my attention t(j the matter. Possiljly
the deejjer or fainter tone of chestnut on the jugular feathers is merely
a matter of age. E\en when \evy prominent, the ruddy area is so
inextensive as to exclude the idea of directly linking the Tsushima
birds with H. squainiceps of the lîonin Islands or with H. pnjeri oi'tlm
Loo-ch()os. In size the Tsushima specimens are as variable as Hondo-
birds and in their average I see no appreciable difference from the latter.
The measurements of Tsushima specimeris are appended below :

Museum
number

Sex.

Length of
wing.

Length
of tail.

Tarsus

Middle toe
with claw

Exposed
culmen

Hemarks.

1697

^

120 mm.

112 mm.

21 mm.

21 umi.

21 nmi.

#

1698
1699

^
^

126 „
124 „

116 „
114 „

23 „
22

23 „
23 „

22A „
25 „

*
(Scarcely any trace of
\ ruddiness on jugular
( feathers.

1700

Î

131 „

118 „

23 „

23 „

25 „

*

1701
1702
1703

130 „
126 „
122 „

122 „
112 „
112 „

22

23 „
22 „

23 „
22
23 „

24 „
23 „
23è „

-*
[The pale chestnut of
j jugular feathers rather
( prominent.

*

1704

t

130 „

119 „

23 „

22

25 „

*

1705
1706
1707

s

133 „
132 „
118 „

123 „

122 „
105 „

23A „
22

22è „

23 „

24 „

26 „
25 „
23 „

#
[The pale cliestuut of
■1 jugular feathers rather
[ prominent.

*

1708

s

132 „

123 „

23è „

23 .,

25 „

»

1709

—

128 „

115 „

22

23 „

25 „

*

1710

^

123 „

115 „

25 „

22

22

1711

s

132 „

117 „

25 ,,

22

23 „

* Jugular feathers suffused with pale chestnut iu varying degrees.

NOTES OX A COLLECTION OF BIRDS FROM TSUSHIMA.

109

Messrs Xauiiye and Tsiicliida also oljtained two specimens of
this species on the island of Iki, Ijetween Tsushima and Kiiishiii.
Both of these are much suffused with ruddy colour on the iu<>-ulum.
The collect(3rs do not remember to ha\'e noticed any difference in the
screeching cry between the Tsushima and Hie Hondo Browai-eared
Bulbuls.

7. Zosterops japonica, T. & s.

Mejiro.

This species is reported to be common on the island. It frequents
Cantellia japonica like Hijpsijjetes aiiiaurods. The tAvo specimens
brought back present the following measurements :

Mus. No.

Sex.

Wing.

Tail.

TarsiLs.

Middlo toe
with claw

Exposed
culmen

1740.

1750.

ad. S
ad. $

59i mm.

tjo „

44 mm.

IS mm.

18 „

li mm.

11 „

13 mm.

]3oth have the bill perceptibly stouter and longer than average
Hondo-specimens, in which the exposed culmen nieasiu-es 10 — 1 1 mm.
The breast and Hanks are somewhat less rufous tlian in nianv Hondo-
specimens, others of which however match exactly in this respect
with the two Tsushima skins now befc-re me. AMietlicr the latter
represent a local race, perhaps intermediate between typical Z. jiiponica
and Z. stejnegeri, I am not prepared to say.

8. Cellia cantillans (T. c^ s.)

Ko-uguisii.

A single female specimen was brought home. The wing me;i-
snres only 55 mm., on which account I refer it to thi.s wpecies.

110 I. iJlMA.

The collectors have very often hcürd the notes of this or the larger
species (C. cantans). I would here remark that the distinctness of
these two forms is exceedingly doul^tful.

V. Regulus crislatus orienlalis, Hoci>.
=■ R. japonicus, P'p.

Kiku-itaclaki.

This is said to he not uncommon on the island. A single
specimen, a female, was ohtained Fehr. 28th.

10. Parus minor, T. & s.

Sliijiukara.

This species was found common in pine-forests. A single female
specimen was secured on Fehr. 19th.

11. Parus varius, T. & s.

Yaniagara.

Common in hushes. Seven specimens, all males, were ohtained
on Fehr. 21st and March 2nd.

i'2. Corvus macrorhynchus, Wagi.

Haöliibutügarayu.

The c()llectors hrought home two specimens of the Oriental
Raven. In gloss of plumage and in having grey hases to feathers,
they agree perfectly with the two races known to occur in Japan,
viz., C. luacrorJnjndnis japo}iensis of Hondo and C. macrorltyiichus levail-
lanti of Loo-choo. In size of hody they are decidedly smaller
than the former, a.pproaching the latter. The measurements are as
follows :

NOTES ON A COLLECTION OF BIRDS FROM TSUSHIMA.

Ill

Mus.
No.

Locality

Dato

Sex

Win»-

Tail-
foather

Tarsus

Middle

toe with

claw

Bill in Height

front of of upper

the nostril mandible

ISU
1S12

Tsushima

Febr.
23rd.

*
Î

316 mm.
31S ,.

204 mm.
20 1 „

ôTîimi.
57 „

53 mm.

54. „

H mm.
39 „

li) mm.

IS „

For sake of comparisoii, I append l)elo\v iiieasiiremeiits ofthe two
races just meinioned.

V. maerorliyiU'hThs japonensis.

Mus.
No.

Looality

Date

Sex.

Wino-

Tail-
feather

Tarsus

Middle j Bill in IleioV,t
toe with front of of upiier
claw the nostril m;indilile

113
U05

Tokyo

Suka-

g-awa

Nov. 28th
1883

Jan. l.st
1891

ad. S
ad. —

349 unn.
340 .,

227 uim.
21(1 „

03 mm.

OO „

55 mm.
53 „

41 nun.
43 „

IS umi.

17è umi.

C. macrorhviichiio levaillanti.

Imp.
Mus.,
T..kvo

Loo-choo

March
13th. ISSO

ad. ^

320 mm. 210 unn.

mm. 50 mm. 37 mm.

1.) mm.

In the above measurements, the height of the upper mandible
was taken bv placing one end of a divider on the cutting edge and
the other on the ciilmen across the centre of nostril.

Of the two specimens from Tsuslvima, one (namely No. 1811)
has the bill almost as slender as the specimen of C. inacrorhijiichus
levaillanti from Loo-choo witli wlii'^li I ha\-e compared it. Witli regard
to the other specimen (Xo. 1812), it is to be stated that the bill is as
thick as in (7. inacrorliyiirltns japniunsis, although in other respects it
ao-rees well with Xo. 1811. T notice however that the curvature of
the culmen is slightly hut perceptibly less arched than in average
specimens of tlie llondo-race. Whether tlie indicated characters are
due simply to immaturity or are to be regarded as pointing to the

112 I. IJIMA.

Loo-dioo race, my knowledge does not reach far enough to decide.
As it is known that the two races intergrade, it is possible that I have
intermediate forms before me.

Tlie collectors very often noticed the thick-hilled raven 1)otli
in towns and on fields, associated with the following species.

13. Corvus corone, L.

Hasliibosogarasu .

This should be qnite common on Tsushima. A single immature
specimen (No. 1813) was brought home.

14. Garrulus japonicus, Bp.

Kakesn, Kasliiflori.

The collectors have met with this species on two occasions,
Febr. 21st and March 6th. Three specimens were obtained,

15. Lanius bucephalus, T. .t s.

Mozn.
A male specimen seen only once and obtained.

10. Motacilla lugens, lutti.

Haku-sekirei.

This was found not so common as in Tokyo. Two specimens,
an adult and an immature male, were brought back.

17. Motacilla leucopsis, GW.

Höjiro-sekirei.

This species, which occurs also in Corea (Taczanowski, Proc.
ZooL Soc, 1888, p. 461), is an addition to the (n-nis of tlie Japanese

NOTES OX A COLLECTIOX OF BIRDS FKOM TSUSHIMA. llo

Empire. Altlioiigli I have no continental specimen to compare witli,
I do not lie.îitate in tlie Jea^t to consider the specimen now Ijefore mc
as of tliis species, as it matches perfectly with Mr. Sh-irpe's descriptii-n
in Brit. Mus. Calalogne, voJ. X. It is a male adiill in full [.hima^-e
(iMus. Xo. 174G). The hlack of the throat is a Jarg'c patch and tlie
base of tlie secondaries is white on hoth webs. Dimensions : Wiu;'-
00 mm. ; Tail-feather 89 mm. ; Tarsus 24 mm. ; Middle toe with claw
17 mm. ; 15ill in Iront of nostril 10!^ nnn.

The specimen was shot March 24th (jn Mitsii-shima, a group of
rocks at the northern end of T.^ushimji. The collectors looked on it
as a.n old example of 21. Uujens ; but it is at once distinguishable by
the absence of black eye- s tripe.

ly. Anlhus spinolella japonicus, (T. k s.)

Taliibari.

A specimen in much aliraded plumage was secured, Febr. 20th.
!'lo<'ks of this bird were observed several times.

I'J. Fringilla sinica, L.

Ko-kawiir<iLi\va.

^ ery common on the island, but only a single male specimen
was obtained.

20. Passer montanus, (L.)

Hnzumc.

Aery abundant near houses as in Hondo. A specimen was
brouuht home.

114

I. IJIMA.

21. Emberiza ciopsis, Bp-

Hnjiro.

? Emberiza castaneiceps, Mooio.

Cliosen-Hôjiro.

E. caslaiii'iceps, origiiitilly known from China, also occurs in
Corea (Gigiioli and Salvadori, I'ruc. Zuol. Soc, 1887, p. 582 ;
Taczanow^ki, ibid., 1888, p. iGb.) On the main islands of Japan it is
represented by E. ciop.'^is, which, so far as I am aware, differs from the
Chinese form only in the males having the ear-coverts hlack (simimer
plumage), or almost black with a slight suffusion of russet (winter
plumage), instead of deep chestnut always. In what points the females
of the tw(j species diifer, I do not know.

Messrs. Xa.miye and Tsuchida collected (jn Tsushima six speci-
mens of lUuiting, all in winter plumage. The following is the list :

Mus.
Xo.

Ijocality

Dalu

Sex

Wiu-

'J'ail-
fcaihcr

Tarsus

Middle

toe with

claw

Expo.sed
culoieu

1751

Tsusliiuia

March IGtii 18'Jl

ad. 3

7ilJllJl.

71 unn.

lOumi.

18 mm.

10 mui.

1752

„

„ Sitl „

,. „

73 „

72 „

13 „

20 „

lo.i ,.

1753

,,

i'V'l.r. I'Jtli „

,, „

7i „

70 „

iSi „

19 „

11 „

175 i

,,

March 2iul „

„ „

73 „

O'J „

I'J „

18 „

10 „

1755

1'Jtli „

c

71 „

•)8 „

I'J „

10 „

10 „

1756

"

,> s

77 ,,

72 „

20 „

20 „

10 „

Of tlie fi\e males, one (No. 1756) was presented to Canon
Tristram, so tliat 1 have now four males before me. ]\Iinute com-
parison of these witli winter specimens of E. ciopsis collected on Hondo,
shows a, close agreement in all respects exce[)t in the colour of tlie
ear-coverts. Namely, two specimens (Nos. 1753 and 1751) have the

NOTES OX A COLLECTION OF BIRDS FROM TSUSHIMA. 115

l)In<'kisli ;nii'i'iil:irs slightly more suffused \v\t]\ rnsset or chestunt limn
in most Hondo specimens ; ])ut then Hondo specimens thnt m-itcU
com])letely in this respect, are not wanfino-. In the third Tsushima
specimen (Xo. 1752), the anricnlars ])ear a russet tone to such a de_"Tee
as is never knowji in F. ciopsis of Hondo. The fourth Tsushim-i
specimen (1751) has the anricidars a. sh;ide more russet ; 1 wonld
simply call it russet-l)rown or deep chestunt. l^nfortunately I h.ave
no speciinen of E. castaneiceps to compare it witli. Perhaps the t^vo
forms are to he considered as intergrading with e:ich other on the
island of Tsushima. It will l)e interesting to know wh(^thw in
suinmer the ear-coverts of the Tsusliima ihrnting tniai hlack oi- remain
suffused with chestnut more or less.

According to ^fr. Sharpe (Jlrit. Mus. Catalogue^ \o]. XI 1, p. 614),
E. rasfanricfps should he wanting the tiny hlack s[)ot on the chin ;
hut that tliis is not always the case, has heen shown hy Canon
Tristram (Ihis, 1880, p. 294). Of the four mak; Tsushima skins
now hefore me, three liave a distinct chin-spot, the forn'th (Xo, 1753)
liaving ili.'it pa.rt destr(^yed hy shot. In true JJ. ciopsis of Hondo,
the chin-spot is mostly wanting ; out of fortv-two male skins that I
examined, only six showed it with any distinctness. The sincle
female skin (Xo. 1755) from Tsushima shows no trace of chin-spot,
agreeing in all respects of colouration with females collected on
Hondo.

In the anKMnit of white on the outer tail-feathers, I see no
apprcci:il)k' dilfcrence hetween Tsushima and Hondo specimens.

j\Iessrs. Xamiye and i'sucliida also collected two jnale specimens
on tlu' island of Iki (Xos. 1824 et 1825). These ha\'e the ear-coverts
agreeing well in coloiu' witli average Iloiidö specimens.

IIG T. TTTMA.

22. Emberiza personala, T.

Awoji.

A mnle speoiiiion o])t;iiiic<l ^[nrcii 2ri(l rnoii^nrc-i : Wii\g^ 70 iinn.;
Tnil-fe.'itliv'T 70 inm.; Tiirsiis 21 nun.: '\ïi<l(lle toe witli r-law 20.\ ^n^n.;
Exposed ciihiiert lOJ, inin. l! diJlvTH eo}isidera])]y in eolonrino' fVom
adult speeimenH colleeu'd oil jfoiidn. Tiie lores are more l)]ack ; the
head, nape, hind-iieck, and sides of head and neck are less olive-green
but ni("/re ashy-o-rey ; the sliglit streak above the ear-coverts is wliitish
instead of snlphnr-yellow ; the cheek-stripe and under parts from throat
to under tail-coverts, wliitish, washed with very p;de sulphur-yellow,
yellower on breast an<l sides ofal)domen. In fact, the yellow of the
plnmaii'e is palei- than T ha\'e ever seen oii Hondo specimens; other-
wise it agrees well with the lal ter. Young, in first win! er plumage?

A male s])ecinien of EiiiJii'riza raridhiJi.'i in immalure phunage
was brought liome from the islaiid of Iki. This s|)ecies has, as far as
I know, never yet l)een reeoi-ded from C'oreii.

28. Emberiza elegans, T.

Miyama-linjivo.

Common on tlie islaiid. Five specimens (-.btained at tlu-ee
different localities, ^[arcli 2nd to 10th.

24. Thriponax richardsi, (Tristram.)

AmanojaknnLa (PI. XII)

Tin's is undoubtediy tlie most interesting species among the
present cohection. Onl}^ a single fem.ale specimen hitlierto existed in
the possession of Canon Tristram, tlie original describer of the speeies
{Pror. Zonl. Soc, 1879, p. 886). :\b'ssrs Xamiye and Tsuchida liad

XOTES ON A rOLLE<'TTON 01' EIRDS FROM TSUSHIMA.

117

siicc('('<leil ill sccin-iiiii- llircc iii:i[!-iiifi(rii1 >])ocitneR.s during' lliciv -^tny
oil Tsiisliiin:!. 'I"lu' InlNfuItiij- i- llicic hililc of m(':i-^iriviHOiits.

: Anle-

lull

Mus.
No.

Loeil'ty

l)a,tri

Sex

Total
[..■not],

Stretrli
of

V\'in-

Tail-
feather

'I'arsus

exter-
nal toe
withonl
claw

from
frontal
fea-
thers

iTsr

K'un<'-in;ik;i

ManOi Sth.
isi»l.

A.1.Î

-.21 nivn.

r'.'lt mm.

-") nun.

iSr. i,n„.

^''f mm.

27.' mm

•'!) mm

17S5

XiiiiunM

., ir.th „

A,!^

'><>2 mm

77.^" mm.

"i.'O mm.

100 mm.

;M' mm.

2(J^ nun.

.">•" mm.

i7sr.

l\niii'-in;ikii

., l:lth ,.

\d.^

ISS IMIU

771- mm

2 17 mm.

ISOu.m

^\ mm.

2(j mm.

•")7 mm

111 tho ;il)(r\-c incnsnrt'inoiits, tlu' total lona'tli and .-^tivtdi of winii's
wore taken li\- tlio rollcctoi-;-; (Vont tlic fresli sju'cimcns. Tlio roloiir of
(lie iiT< .--hoiild 1)(' clciir i/rUow. not lilack as iT'])r('.^('nt('(l in ('anon
'riislraiii's l\(j;nvo (he. cit. Tl. XXXI). «rr a.-^ (juotcd by ^Tr. Ilaru'ilt
(ßrit. i)/"«.^. Cr//., vol. XVTII. ]). oOG) from Pudiards the collcct.^r of
ilic tv])e sp('<'inien. lîill liornv l)Iack, cadi mandible Atitli a small
diill-wliiti.dt spot at tlie ti]) of etitting edi>-<'; tarsus and toes Itlaek;
claws liorny-klack.

'Ï\\Q deseription of adidi female ])liima,U'e .as o'i\('ii by ^Fr. llai'iiatt
(Inc. cit.) from the type speeiinxMi tallies ^vell witli tlie two female skins
now Iv'fore tne. 'i'lie male n,i;-rees witli th(i female in all respects ex-
cept in Itavinu' tlie same sexual df-tinction of red on the head possessed
hv its cong-enors, as had been forelold ])y ( aiion Tristram twelve years
a<i'o. As r })resnme that s])ecimens of tliis species Avill continue to be
rare anionu" collections, T insei-t tlie folIo\vini:' des(aa'])tioii of ilie
])Iiimaa'e.

Adult male. TJic prcviiiJmj colour is hJac],- or deco ln-ownisJi-
hhtch. villi rxcrpiiom In he im'iifionrd in the seniicl. FralJuTs of lliis
colour hiire (jeucrallu darl' grcij Imsrs, ond ihosr of the hind tied,-, tlie iippcr

118 I. I.JIMA.

hacJc, tlia side of neck, llic ear -cor ni s , tlic smaller wimj-corerts, the loivcr
tliroaf and tlie upper hreeist slioir a rarijing deijree of (jreenish gloss. On
the upper hach this is tJie most inJense, and here as on the upper hreast, it
is seen as restricted to the rather ivell -defined, narroiv margined zone of fea-
thers. Forehead, crown and. elongated, occipital crest bright crimson, the
feathers having the liasal pari white and the extreme hase dark greg.
Broad malar stripe also crimson, hut someudiat duller, each feather with a
smidl wlrilisti jiatcli near the ]):ise which is dnrl: greg. Nasal bristles hlacJi
with smol'.ii-brown bases, ('hin and upper throat darl: smolij-greg. gradual-
hf passing info the Itrownish-hlacJi witlr greenish -black gloss of the lower
throat. The latter is tlmig strealaul with short while lines, caused hg the
marginal lips of liarbs bi'ing of that colour. A few simihir sireal's also
found on posl'}n<dar featlicrs and. a patch of them just behind the ear-
coverts. JjOwer bad' and ruuip silltj irliite, the exposed, parts of feathers
hearing a slight J)Uli)j tinge. J few feathers along the anterior border rf
tlris while area have more or hss Jdaclc on thrm, leaving the tips white : this
can onhj be recognized bi/ raisitng the feathers. Some few hindmost feathers
of' the lou-('r rumji have a Itlacl' spot near the lip, varging in shape and size.
The tuw) centred, featliers of the upper tail-coverts are white with a large
irregular spot of Idacl' on their apical portion : but when ihe featlters ef the
rump are not raised, theg liave the appearance of being black margined with
ivhite, as Mr. Jlargitt obst rves. Six primaries (2nd to 7th) lipped with
white, broadest on the :jrd, dth and ■)th prim'trg, narrowest on the outer web
of the 7lh. jirimani. liases ef all primaries and second'iries white with a
slight tinge of i/ellow. the former onhj on the inner web (to the extent (f
about IS mm. on. the 1st and edioul SO mm. on the -Ird pri]ivtrg) : the latter
on bnlh webs (to ihe extent of 70 -SO mm. on the inuer web i. Cnder wing-
coverls moslhj wliite with a gellon-isli tinge, some feathers near the edge of ihe
wing lieing niarh'd. with V'irifing amenint (f darl-brown, udiereas iJn' edge
itself is lilacli with greenisli gloss. Axilh(ries, the entire sides of the bodg.

NOTES OX A COLLEOTIOX OF BlltDS FKOxM TöUÖlIIMA. 119

loîvcr hrcdxl and tipper ahdomtn, wliilc u-'ilh a dight yelhmish or huffy
tinge, llie feathers Jiacing lite cxiretne huse durk-greij and (lie rent of huml
porlion sil/üj while, assuming (lie above -me iidoned liiige lonards (he exj)Oxrd
apiced porlion. The black feathers of the breast in close proxintitg to (hf
while area are margined at the lip with buify while. Lotrer cdidonunal
feathers black and also margined with buji'ij while. Thigh-feathers ivilh a
large black area, presenting the appearance of being likewise black and
margined with bully white. Tibial feathers with a brownisli-black marking,
leaving the lips bufl'y-while and ihe Ixisal parts wliitish. Shafts of quills
and of tail-feathers deep brownish-black.

Adult Icinule. I/ikc the male in plumage, e.ccepl thai the head is
entirelij wanting in red. The feathers of the forehead, crvwn and occipital
crest, as also of the malar region black with greenish gloss, the bases of fea-
thers being dark grey. The greenish glass of the upper back less intense
them in Ihe male. On one (Xo. J 71^6) of the tiro female skins, ihe short
1st primarij is tipped with while, which, is not the case on the other
specimen; the six follow ing primaries have always while tips as m the
mede.

Of the habit of thi^< s|iecic8, and of othei" points coiiceriiiuii" it,
Mes8r8. XaniiN'c and 'I'siicliida haM' kindly su})plicd nie with ijialei-ials
for the followin;Li' account.

On }.larch 3rd, while passing through the deep forest of Tadera
(ahout 15 miles to south-west of îzuhara), (heir attention was called
to a strange piercing cry re[)eated a few^ times. Whence it emanated
they could n(jt tell, biit imagined it was something like the shriek of
some hawk's nestling. They waited for many minutes cx[)ecting to
hear it once again, hut in ^•ain, and as no sign of any auimal was
tliscernihie, they mo\'cd on, little thinking that they had just heard
the l(jng-sought 'Thriponax richardsi, as subsequent experience taught

120

I. IJIMA.

thtjiii. A few days later, the l)ii-(l itself was si^'lited fjr the first time
at a ^illao•e called Kuiie-iiiaka. Its cry is very characteristic and
S(juiids somewhat like a ])rol(jij;u'ed '' iu/«//,'" alike in hotli sexes, verv
loud and heard for a great distance. This it repeats at intervals
when on the win^' as well as when clindjini»' trees. Oidv in the latter
case, each single " 7u/a/< " is less prolonged. besides the localities
ah-eady mentioned, Messrs. Xamiye and Tsuchida observed the hird
also in the villages of Xii, Takesliiki, Mitsune, »Sago, Sumo, ^.^c. The
specimens now^ in the Science College were shot, ;i pair at Kune-inaka
and a second female at Xii, as v\'ill be seen from the list I have given.
It is needless to say that the collectors made special endeavours to
secure more specimens ; but the Avariness and the rapid movemeiits
of this bird made approach dilhcult and ottered but little chances of
a shot. The collectors' own (observations and the answers ot natives
to iiKpiiries made at various localities, prove that tlii- fine wood[)ecker
is by n(j means rare on Tsushima.

It finds its abode in dense, more or less- exten.>i> e forests of tall
pines, firs, crv[)tomeria.s, oaks, c;implior-trees Sec, Such a forest
usuallv exists in valleys between hills, and is known to natlNcs as
huromi (a darlc [)lace). The bird is never found in any nundjcrs
together ; perhaps a [)air is the utmost that a huromi might
harbour. Standing on the hill-to|), one hears its peculiar cry and
loud ta])pings at some considera,ble distance in the w<joded ^alley
Ijcneath; he descends to tlie spot probably to find the bird g<jne, but
some chi[>}>ings ot bark or wood strewn on the ground, and some bare
places on the tree-stem a.bo\e tells him the wo,rk it was recentlx' busy
at. Dead trees or bran<'lies naturally attract it when in search of
fjod, and it is said that the bird goes regular rounds to its fnoiiritc
trees every dav. Should one of its ti'ces be rec()gniyed, a collector
wotdd do well therefore to lie in andjusli awaitimi' its arrival. Its

NOTES OX A COLLECTION OF BIRDS FlîOM TSUSHIMA. 121

maiURT of fliuht i.s siiiiilp.r to tluit of otlier woodpeckers. The collectors
have often marked the spot where tlie liird alighted, aiid on more
than one occasion, tliey discovered it ag'ain on flic (jrinivil. Avhence it
climbed up a tree-trunk in the nsual manner on tlieir ap[)roach, [ do
not know whether a similar hahit has ever Ijeen noticed in any other
woodpecker.

The lower classes of the inhabitants of Tsushima hold this bird
in some deuree of religious awe. Some natives, as Mr. Xamiye tells
me, indulu'c in the superstiti()ri that when I)udd]ia was in the process
of creating man, a certain being called aina-no-jaliuma pressed to lune
a certain part put on his forehead instead of much lower down on his
body, and that that being was none else than the woodpecker in (jues-
tion. Hence the natives call this bird h\ that name. In ordinary
•lapanese, amn-no-jaliu or amd-no-jdhimu (evidently of buddhistic origin)
is an appellation gi\en t() a cross-minded person.

'1Ö. lyngipicus kisuki, (T.)

Kogem.

1 he t\pical foriu lound on the Hondo also occurs (jn Tsushima.
It Avas tound to Ik; \ei"y common. Six s])ccimens were obtained
l)etwecn Fel)r. 19th aiid March IDtli. T'hey agree in colour and
markings -with specimen.-; collecteil in Provinces Sagami and llida.

i^(i. Turlur gelaslis, (T.i

Kijiljiito.

Abundant on the island. Xine specimens (jbtained. Length of
wing, measured from the cai-])al joint, 183 — 197 mm.

122

I. IJIMA.

27. Phalacrocorax capiMalus (ï. & s.)

Bliiiuatsn.
Abiiiidaiit on rocky shore.s. A specimen brought back.

28. Ardea cinerea L.

Aosagi.

An adult ypeciuien bi'(3Ught home was the only individual that
was seen on the island.

29. Ardea jugularis, Wagi.

Knrosagi.

On Mitsusliima, a group of rocks at the northern end of Tsu-
shima, tlie collectors, have met with a flock of this Ijird already
known to inliabit the island through the collections of Jouy and
Uino-er. It was exceedingly difficult to approach. Two line speci-
mens were seciu-ed.

Mns. Xo.

j
Locality & date

Sex

Wing

Tail-
feather

Tai-sus

Middle

toe

without

claw.

Exposed
culmen

1802
1803

Mitsushiuia, March 20th 1891

Ad. ^
Ad. ^

290 mm.
284 mm.

112 mm.
105 mm.

80 mm.
78 mm.

58 umi.
55 mm.

83 Limi.
81 umi.

T(jta] length and stretch of wings, as measured by the collectors,
were 640 mm. and 1004 mm. in Xo. 1802, 627 mm. and 1041 mm.
in No. 1803, respectively.

Dr. Stejneger has erected the grey Keef -heron of Tsushima into
a distinct species, Dcmiegretta ringcri, for the reason that the top
of head and the occipital crest are plumbious and ligliter than the
Ijack {rroc. U. S. Nat. Mus., 1887, p. 300). On the two specimens

NOTES OX A COLLECTION OF BIRDS FROM TSUSHIMA.

123

before me, T fail to see tliis distinction ; hence T have j^'efeiTed to
retain Wao-ler's name, as 'Slv. Seehohm does in liis Jl.'rJs of tin'
Japniie^c Euiinr('.

The white on the chin and throat seems to be ([nilc \:'riable in
amoniit. On one specimen Qso. 1802), it is a narrow iii1errn[>ted
streak, wliile (^n the other it is represerited by a broad large patcli on
tlie upper throat fo]h)wed l)y some tliree little spots.

The white lln-m of Keef-lieron was not observed.

Î50. Anas formosa, Georoi.

A;i-eriuno ; Touioye-ganio.
A male sppri?nen wai^! shot at Xiimura, March 16th.

;n. Anas galericulata, L.

( tsliidovi.
A male specimen was ol)faiii('d also at Xiimura on tlie same day.

Î32. AIca carbo, (Pall.)

Kf'iinafnvi.

A specimen (sexed $ with query, ^lu.'. Xo. 1787) was sliot near
Ofnnako.slii. ^Fareli 27t:li. This was the onlv individual tliat tlie
collectors have met with. It is in mature plumage with remiges and
rectrices much abraded. Amongst otlier localities this species also
occurs in Olga ]^)ay ((«i^'lioli & S-jls'adori, Froc. Zool. Soc, 1887, ]>.
593).

33. AIca anliqua, Gm.

Umi-snziimo.
On March 15th a specimen was sliot at Sagamura. A few days

124 T. TJIMA.

later five specimens were secured at Ina-ura,. They were found in
flt^cks.

34. AIca wumizusume, d.)

Kanmnvi-nniisTiznmo.

A pair of this rave hi rd was ohserved and «»ik' of tlieni (Mus. Xo.
1783) secured, near Öfnnadvoshi. ]\[arch 27th. Tlie s])ecinien ohtained
is a male and is fin-nished with a l)lack occipital nvi^t.

85. Fratercula monocerata, i\\\M)

Utö.

'I'his species was common, mostly found in pairs. Five specimens
were ohtained at tln-ee or four ])oints on tlie C(\ast, AEarch 18th. The
horuv projection ahove the nostrils is in various degrees of development,
fnll}^ de\el(^ped on only one specimen.

3(i. Larus cachinnans, rail.

Segiu'o-laimome.

There are among the collection two specimens of Herring (inlls,
wliich I refer to this species. 'We one, shot (^n ^litsushima, March
25th, is an adult, measuring 366 mm. in the wing (Mus. Xo. 1815).
The other ol)tained at Azama, ^farcli ôtli. is in young plumage, the
wing measuring 317 mm. (Mus. iSo. lcS17).

37. Larus vegae, (PaimciO.

In 18901 sent to Dr. Stejneger for identification three specimens
of Herrino- (udl, collected at or near Tokv(3. Tliev were returned
to me identified as L. vegac, a species originally discovered on
the coast of Tchuski Land hy the " Vega " expedition and descrihed

^^)TES ox A OOLLECTIOX OF HIRDS FltOI\[ TSUSHIIMA. 125

l)v Piiliiién iiinlci- tlie name of L. argi'nlatu<;. \ur. vrqar CBidrag Sil)ir.
fsliafsl'. Lotii'lftiUHd ]'('ijii-cxpcdiiion''''). Tlic sninc species was also
i'oniul l)v Dr. liimu'c on tlic f^iakoji' fsl.-inds (/<*•///•. z. Kenntu. d. Jliiss.
Ficichr^ II. (1. angreiizi'inJi'H Lihuh'v Jx/Vz/.s-j"). Xow, tliere is anion«''
the present eollection fmni Tsii .liinia an adiilr specinKMi of Hei-i-iii^-
(Hill (Mus. Xo. ISKî. obtained at Kiita. I^'hr. 20Mi) wliirji a,uTees
eoin])letely with those identified by Dr. Stejne,n-er as Jj. vrgac. It is
very niiich h'kc 1j. cachiiDian^ hut smaller. 'I'otal len^'th (120 mm.
(aLfaiiist 710 mm, of adult Tj. cachiniKvm, (Afiis, Xo. 1815), wing
^WIS mm. (a_u"ainsr 866 mm.), middle toe Avith claw 61 mm. (aii'ainst
68 mm.), exjioscd ciilincii 5n mm. (aL;-aiiist 6! mm.).

HM. Larus crassirostris, \iriii.

I iiii-iH'kd.
'l\vo ndiilr s])('cini('iis Avere ohfaincd.

80. Larus canus, J-.

Karanino.
A specimen in immature phima^'e oI)taiii('(l.

ii>. Haematopus osculans, Swinh.

3riy;il\(>(1()i-i.

Abundant on Mitsiishima, at the northern extremit\' of Tsudiima.
Three specimens obtained.

The Avhite on the outside AA'eb of the primaries appears on one
specimen (^[us. Xo. 1799) on tiie fiftli and on another on the sixtli
(piill, Avhile the third specimen (Mus. Xo. 1800) slu^ws a mere streak
of it on the fifth (piilL

* t These works have reuiained inaccessible to uie, and aj'o known to uie only tlirou^h
Mr. Seebohm''s account in Ihh, ISSS, p. .3i9.

] 2(S T. T.TIMA.

Ji. Numenius cyanopus, Vioiii.

Hnrolai-sliigi.

A specimen was oiioe met witli and .secured, on tlie sea- shore at
Kônra. ^[arch 1 Itli. It is a. femaJe ^vitli tiie ex]X)sed cülmen IS'2
mm. long.

42. Totanus fuscus, (L.)

Tsinni-sliigi.

A female in winter ])lumag-e was shot at Xii-mnra. ]\iarch IGtli.
That Avas the oidv time lliat this species was ol)served.

4.n. Totanus glareola, (L)

Tiikal)U-slii,t];i.
A female was shot at Ki^moda, Api-il 1st.

44. Totanus hypoleucus, iL.)

^rnsliibami-shigi.
A male obtained at Wa.ni-nra, ^[arch 23rd.

4'. Colymbus arcticus, L.

Ohamn.

Tliis species was ofteri met Avirli. A female in innntitiire plumage
Avas ohtained. Ahove, hrownish black, witli lew white spots on wing-
coverts ; below, white from tlie chin. Wing 182 mm., exposed culmen
50 mm.

NOTES OX A COLLECTION OF BIRDS FROM TSUSHIMA. 127

■in. Podiceps rubricollis major, T. i^ s.

A kano(lo-kiiitsnnnn-i .

A fine pair was f^hot .at Takeshiki, April 1st. ^[ale (with
chestnut tliroat) and female measure respüeti\eiy 181 mm. and
180 mm. in wing-, 50 mm. and 48 nmi. in exposed eulmen.

47. Podiceps cornulus, i^hn.)

]\Iiiui-kaitsnmiu-i.

A specimen was only once met with and ohtained at Ina-ura,
Mardi 21st. It is a female in winter plumage. AVing 135 mm.,
exposed eulmen 22 mm.

48. Phasianus lorqualus, Gm.

Körai-kiji.

This is the common pheasant of Tsushima. P. versicolor is not
found. Three males and one female were ohtained at the villages of
Uchivama, Kune-inaka and Ku(a. Ft is said to he most ahundant at
O-ura, a village not iar from izuliara. i lia\e no continental speci-
mens to compai'e witli.

In an aiitheniic inanus('ri[)t woi'k entith'd '' Tsiislilina l\.iri;aka''
(^0-%^^^-> treating of the g-eogra[>]iy, liisioiy, and natural pi-oducts
of Tsushima, written ahout 190 years ago) l)y Suyaiua, it is stated (liat
j)heasants are said t(,) have been originally entirely wanting on the
island and to have been first introduced in the middle ages on I nijima
(at the northern extiemity of Tsusliima), whence they spread over the
island proper. In another old manuscript " TsusJiiiiia-Kiji " (j_^ ^ fg :^,
a voluminous work of similar natur'c and eijually aiithentie) 1)y llira-
yama, there stands a statement to the same ett'ect only more definite.

128 I. IJIMA.

In this connection ] nuiy mention th;it in the first named woik
I find a statement that tlie phea.sants of rlishima (a small island off'
the coast of the province of Chiknzen, Kinshin) are the same as those
of Tsushima, as the result of transplantation from the latter island,
llino Kanroku in his ornithological work (" Yökin-]\[onogatari,"
Narratives on Bird-keeping, written ahout 90 years ago) has also left
a record of the Corean pheasant being introduced and made to thrive
on some island off the western coast of Kiushiu (one of the Hirato

group?).

On the Formation of the Germinal
Layers in Petromyzon.

By

S. Malta,

Zoulugical Laboratory, Science Collège.

With Plates XIII. ami XIV.

In spite of the fact that .se\eral eininent investigator« have lu^en
eno-ao-ecl in studyino- the enihryoloo-y of the Cyclostoinata, the develop-
ment of Petromyzon presents as yet many points ^vhich remain
obscure or which are stated in contradictory terms ])y different writers.
The present investigation was undertaken to throw hght on some of
these points. It was carried on during the academic year of 1890-91
in tlie Zoological Laboratory of the Science Cc^llege, under the su[)er-
.vision of Prof-^. K. .Mitsukuri and I. Ijimn. I may, in ihis ])]ace, be
permitted to express my sincere thanks for tlu" vahial)le advice winch
they have o-i\en during my work, and the kind manner in wliich they
have forwarded my researches.

The species which I have studied is prt)b;il)ly either l\(ron}tjzon.
planevl or a variety of it. The larger part of tlie materisds used was
collected and preserved l^y Prof. Mitsukuri during the month (jf Feljru-
ary, 1890, in fresh- water streamlets ])et\veen paddy-fields near the t(jwn

130 s. HATTA.

of Gull, and my special thanks are due to him for placing them at my
disposal. The other part of the materials was obtained by myself at the
same place during the spring of the present year (1891). We wish to
express our deep obligations to Mr. Nawa, the enthusiastic naturalist
of Gifu, without whose aid we could not have succeeded in obtaining
the objects of our search, and to the authorities of the Middle, and of
the jS^orma], Schools of that town for affording us laboratory accom-
modation.

The eggs and larvœ were hardened partly in Kleinenberg's picro-
sulphuric acid, and partly in corrossive sublimate. A few larvœ were
also killed in Flemming's solution. The sublimate specimens gave
the best results, although good sections were obtained in all cases.
Acids, on the whole, had the effect of making yolk-granules highly
refractive, and thus greatly increased the difficulties of observation.

As to the staining fluids, picro-carmine gave by f;xr the most
satisfsictory results. This, being the nuclear stain and not affecting
yolk granules, made observation comparatively easy. Other colouring
fluids like borax-carmine or haematoxylin (of Kleinenberg as well as
of l>(jhmer) stained diffusely both the protoplasm and the nuclei, and
above all, were most unsuited for my purpose from the fact that they
stained yolk granules the deepest.

Tlie age of the eggs and of the lar^-œ was not determined by the
actual time elapsed, but by their appearances as opaque objects and by
their structure as shown by sections.

Care was taken to have sections of each stage made in several
planes so as to enable us to obtain as accurate an idea as possible of it.

1 shall give the results of my investigation under the following-
heads : —

1. The (lastrulation.

2. The Formation of the Mesoblast.

ox THE FORMATION OF THE GERIMIXAL I,AYEKS IN PETROMYZON.

131

I. The Gastrulation.

My <)l).sei'vah<)iis on ^^eginetitiiig' ("-gg^i are too iiicoinj)]('r(' to
eiialjle me to make any definite ytuiement in regard to the process.
The earliest staire on which I wish to ofier remarks is that of the
oldest morula. \\ hen this is viewed as an o{)a<jue oljjeei", the animal
pole and the vegetaHve pole ean ])e exiernally distinguished: tlie former
is whitish and somewhat translucent hoth in fresli and in hardened
specimens, w^hile the latter is opa(p!e and of a p>ale yellow colour. A
slio-ht depression o'oes round the eo-o- niarkini»- the Ijoundarv between
these two portions.

In sections (tig. 1) the contrast of the two portions is well
l)rought out. A spacious segmentation cavity is placed excentrically
in tlie egg and occupies the whole interior of the anim;d pole. The
cells forming the roof of this cavity are arranged in 2-4 layers and,
compared with the cells of the opposite pole, are smaller, comparatively
free from yolk gj-anules^-and have smaller nuclei VN'hich stain ori the
whole deeper. The cells forming tlie floor of tlie segmentatioii cavity
are 7-8 deep, full of yolk-granules with other cliaracters as indicated
above. All the cells are po!yg<vnal in sliape, evidently througli mutual
pressure.

The next step of development consists in the gradual thinning
out of the roof of the segmentation cavity. ()])inions differ iri regard
to the extent to Avhich this process is carried before gastrulation sets
in. According to Scott^ and Shipley," the roof of tlie cavity becomes
one cell layered before the gastrulation begins. On the other hand.

1. W. B. ScoU : -Boitr;i;4e zur Entwicklungsgeschichte der Petrouiyzon. Morph. Jahr)).
Bd. VII.

2. A. E. Shipley:— On sotii'^ points iti the Developuient of Pi'li-om'izon tlui:i<itili>i. gii:i''"fc-
Jouru. Micr. Sei., Vol. 27.

132 s. H ATTA.

iviipffer' maiiitnin.s tlud tlie process of invag-ination takes place, at the
same time as tlie ditterentia.tion of the epiblast. lie states further :
" EJie der Vonjawj der Blaslodermhildang d<e Region der grossfen Zellen an
Gegenpo^ erreich' liât, erschein hereita der Blasioporm. ])as Blaslidasia-
dium is liier also ver],Urz(, die Bildunij der Blislospliiire coincidirt mil
dem Beginn der Ga^trulatim.^'

Although I can not be positive ssboiit this point, my observations
tend to conhum the views of Kuptfe?-. Amorjg a niimljer of sections
belonoing to these stages, I can not iind a single one which lias the
roof of the segmentation cavity consisting of ti single layer of cells. I
have, however, one series in which I think the process of invagination
is just ready to l)egin. T have figured a section of this series in fig. 2.
11. Xlir. It will be seen that in this egg a portion of the side wall of the
seo-mentation cavitv is thinned out into one laver of cells wliich haAe
assumed a regular columnar sha])e. This is probably the point where
invao-ination 1)egins, and possibly corresponds witli the differentiated
region in fig. 10 of Knpffer's paper. The rest of tlie roof of the seg-
mentation cavity is still two to three cells thick. I have also some
efro-s, in which, while the gastrulation is going on, the roof of tlie
segmentation cavity is in some places one cell and in other ])laces two
cells thick. In such cases, wherever the roof consists of a single
laver, the cells assume a colamnar shape, different from the irregular
polygonal shapes of earlier stages.

As to the manner in which the roof of tl\e segmentation cavity
thins out, previous writers seem to consider that it is brought about
l)y the inner cells of the roof passing round to the sides and to the
floor of the segmentation cavit}^, while the outermost layer of cells
becomes the definitive epiblast. If the upper cells passed really to the
sides aud to the floor of the segmentation cavity, they ought to be

1. C. Knpffer: — Die Entwicklung von Petromyzon Planeri. Arch. f. Miki-os. Amt. Bd. 35.

ox THE FORMATION OF T]IE GERMINAL LAYERS IX PETROMYZOX. 133

easily rcc()_i:^ni/.ed in the.se parts, especiaiJy on the floor, as they are so
niarkedlv diHeivni Irom the f'ells of the vegetative pole. Any trace of
sncli miiii-al ion is liowever not to Ije found. I am strono-]y inclined to be-
lieve that the t^liinning out: i.s !)ronght ah(Hit by the cells of different layers
in tlie roof oftiie .-egnietitation cavity wedging themselves in between
one anotlier, tliiis gradually rt^lucing the nundjer of layers. As this
|)rocev> of wedging in ne^'essarily increases the siiperiicial extension
the cells are a])le to spread themselves \o the invaginated tube as well
as over the cells of the \egerati\o ])o]e ))y epibole during the gastrula-
tion. rien''e the thinninu' out is continued and carried on at the time
that the invagination is ta.king ])lace. .Vccording to this view, the
definitive epiblast is not formed necessarily by the cells which formed
tlie outermost layer of the animal ])o!e in earlier stages, but by those
which were left after other cells have been invaginated.

The ga.4rulation now c-ijurmeru'es. l*^gg-^ undergoing this process

s1io\v several inarked clianges even wlien viewed as opaque objects.

In the first place they ac(piire the ap|)erirance of being solid and firm,

no di)ul)t in consequence of the obhteration of the segmentation cavity.

Thev also decrease in their absolute size, as can be easily perceived by

tlie naked eye. This nnist necessarily be the case when we remember

that a large portion of the cells is in\agiiiated into the inside of the

eo'i»". Tlie shape of the e"'o- also undero-oes chano-e. Instead of bein£>- al-
oe 1 an o o Ü3

most Spherical a.> hithertof(_)re, they have become more or less elongated
in the longitudinal axis of the future embryo. The anterior end can
now be told from the posterior, as the former is rounded, while the
latter is pointed. The dorsal surface can likewise l)e distinguished
from tlie ventral, as the former shows a faint median ridge. Thus the
egg assumes a distinct bilateral symmetry.

The internal changes accompanying these alterations in outward

134 s. HATTA.

appearance can be g'athered from ûgs. 2, o, and 4, PJ. XIII. As al-
ready stated, I am inclined to believe that fig. 2 shows the stage in
which the invagination is just commencing. The cells where this process
beo-ins (pp. fig. 2) assume first of all a columnar shape, while the rest
still remain materially unchanged. Once begun, tlie invagination pro-
gresses rapidly, the roof of the invaginated tube being formed by the
cells coming from the animal pole, while its floor is furnished by the
yolk cells. According to Shipley (loc. cit.) and Kuptfer (loc. cit.),
the epiblast extends itself over the vegetative half of the egg by the
conversion of the outermost row of yolk-cells into small columnar
cells. This appears to me very doubtful. I think it more prol^able
that the whole yolk-cells are bodily invaginated into the interior, i. e.,
the point marked x in fig. 2 moves itself constantly towards the
l)lastopore Qrp.), so that the whole mass of yolk-cells is really pushed
inside. According to this view, what was at first the external surfîice
of the yolk-cell mass, becomes the lioor of the invaginated tube. The
seo'mentation- cavity is pushed forwards and early obliterated. This
process is very much like that described by Hertwig^ in Triton.

Tio-, 4 represents a median sagittal section through an egg in
wliich the invagination is almost completed. Fig. 3 is a transverse
section of an egg a little younger. From these two sections some idea of
the character and disposition of the cells forming the différent layers can
be easily formed. The roof of the mesenteron consists from the first of
a single layer of columnar cells appressed against the under surface of
the epiblast. I could not find throughout the entire extent of the in-
vaoinated tube, either in longitudinal or transverse series, any trace of
cells interposed between the epiblast and hypoblast. I can not therefore
accept Scott's invaginated mcmhhi^i (loc. cit.), nor can I find any trace
of Kupffer's teloblast (loc. cit.). The epiblast cells are also columnar

1. 0. Hertwig :— Die Entwicklung des mittleren Keimblattes der Wirbelthiere. Jena, 18S3.

ON THE FORMATION OF THE GERMINAL LAYERS IN PETROMYZON. 135

but smaller and less tall than the hypoblast cells. Then- cell-limits
are also more distinct, Tlie floor of the invaginated tube is formed by
the upper row of y(jlk-cells, which have assumed a more or less
columnar shape.

I wish to emphasize liere the fact that the invaginated tube is not
the same as the cavity ^of the future mesenteron. As the subsequent
history shows, the whole mass of yolk-cells is absorbed with the
exception of the outermost row lying immediately inside the epiblast.
This latter l)ecomes the definitive hypoblast (fig. 27 and fig. 19).
Substantially tlie same tiling has been shown ])y Scott (/. c. pp. 121-
122), except that he regards the outermost row as destined to form the
mesoblast, and the row next inside as forming the definitive hypoblast.
AVhen once we remember the above fact, one can easily perceive that
what Kupffer belicNes to be the liver, in his figs. 27 and 28 (e), could
not be such. This org;in can notarise among the cells which are after-
wards absorbed. 1 am inclined U) think that what he calls the liver
in liis fig. 28 is the slit which tu'ises between the main body of yolk-
cells and its outermost row (cf fig. 27).

ÏÎ. The Formation of the Mesoblast.

At about the time when the gastnilation is ahnost completed, the
eo-o' underofoes one (^i' the most important changes. To the two
primary layers already dealt with, a, third layer, the mesoblast, is
added. The formation of this layer forms one of the most difticuh
subjects in the study of the embryology of Pelroiwjzon. The altera-
tions at first met with are altogether in the internal structure and can
therefore be made out only in sections.

136

s. HATTA.

For the sake of convenience, I shall treat of the meso])last under
the following heads : —

A. The mesoblast in the neighbourhood of tlie blastopore
(or the peristomal mesoblast of Rabl)

1). The mesoblast on each side of the dorsal axial organs
(or the gastral mesoblast of Rabl)

C. The lateral and ventral portions of the mesoblast.

D. The metameric segmentation of the mesoblast.

A. Tiie inesobhist in ihe neighbourhood of the blastopore, (or the
Peristomul Mesoblast of Rid:)l) has never yet been described in Petromyzon
Ijy ])revious writers. I have, however, obtained sections from which it
appears to me safe to conclude that meso])last cells are budded out from
all arouiid the lip of the blastopore except the dorsal median point where
the epiblast turns round to join tlie hypoblast. Fig. 5 represents the
median sagittal section through an egg in which the gastrulation is
already completed. In this ligure, we find tlie floor of the invaginated
tube fn'med, for a sh(n"t distance from tlie ])lastoporic opening, of
specially small cells. In continuation with this stretch of small cells,
there is seen a Avedge-sha[)ed aggregation of similar small cells (^mes.
p.) extendi iig ventrally between yolk-cells and the epiljlast. It is
marked off from the epibdast i)y a slit, while it lies in contact witli
yolk-cells and is marked off fr(3m these only by the small size of its <-oyi-
stituent elements. In this mass, as well as in the stretch of sn.ia 11
cells forming M.ie floor of the invaginated tube, many karyokinetic
figures are seen arid testify to the fact that cells are very raj^idly
mu]ti])lying in tliis region. This mass is in my opinion tlie pcristo-
iiuil iiicsoblas! (('f Rabl).

Fig. G is a section from the same series passing through the
lateral li]) of the Idastopore. Mere we find a mas^ of similar small

ON THE FORMATION OF THE GERMINAL LAYERS IN PETROMYZOX. 137

cells, iiitcrNciiiiii^' Ijctwecn yolk cells and the epiblast, and stretching'
not only ventrally but also doryally.

In enibry(j:3 a little more advanced, these relations are much more
clearly brought out. Fig. 7 is the median sagittal section of sucli an
embryo. A\ e again find the mass of small cells budded out from cells
forming the floor of the invaginated tulje for a short distance from the
entrance.

Figs. 8-1 1 are a series of frontal sections from an emljryo of about
the same stjige. Fig. 11 is the most posterior representecL It passes
through the line ah in fig. 12. i.e., just through the ventral li[) of the
blastopore. Here tlie mesoblustic mass which is distinguished l)v the
small size of its cells and the intensive staining of their nuclei, is not
paired but is continuous across, being interposed between the epiblast
and the yolk-cells. The median j)ortion <3f it is continuc^us with the
epiblast and reminds us strijngly of a section through the primitive
streak of hifj'her vertebrates, with which it is no doubt homoLjo-ous.
Fiu'. 10 shows the section i);issini>" throui>'h the line cd in hu'. 12.
Tlie mesoblastic mass is on the whole paired but still continuous
across the median line, as the section is not vet out of the region
wliere mesoblast cells nre lacing budded out from the floor of the
invaii'inated tube. Fiü'. 9 is throuHi the line ef in fi"-. 12. The
mesoblastic mass is distinctly paired in this section, and [)asses in front
int(j the ufastral mesoljlast in fig. 8. The.se facts are suiBcient, I
think, to justify my conclusion stated above, viz : that mesoblnst cells
are budded out from all around the lip of the blastopore except the
dorsal median point.

V). The gastral Mesohlaal . In the region of Ûïq body anterior to
the blastoporic opening, the mesoblast arises as paired masses, one on
each side of the c\n)V(\\\.- anläge. The manner in which this mass is
formed, is fundamentally the same througliout every portion where

138 s. HATTA.

it is found ; Ijiit in different regions, it presents some modifications.
In the ceplialo-cervicnl region, the process has retained best its primi-
tive characteristics, while in the region of the trunk, it has become
altered to a great degree, owing no doubt to tlie presence of the yolk-
cells. On this account, we sliall begin with the description of the
mesoblast formation in the first named region, although in point of
time it is formed latest in this part, as the formation of the gastral
mesoblast proceeds from Ijehind forwards.

As has been shown by Scott, (/. c, Taf. A^III, fig. 10 b) the head
is formed Ijy the Ijlind end of the invaginated tube protruding itself
above the oeneral surface of the eo'i>'. The head when first formed is

O CO

thus a double- walled tube — the wall of the inva^-inated tube bein«:
enclosed by the epiblast. Fig. 19 is a section from near the blind end
of the invaginated tube at the time when the head is ready to protrude.
The lumen of the invaginated tulje is here more expanded than further
behind. Its roof is formed by a regular columnar epithelium in
contact with the epiblast. Adapting itself to the slightly thickened
medullary ])late, the columnar epithelium is slightly bulged out down-
wards in the median line. This median part becomes afterwards the
chorda dorsah's while the part immediately adjacent to it on each side
forms the gastral mesoblast. J.aterally, in continuation with the
epithelium of the invaginated tulje, the outermost row of the yolk-cells
is arranging themselves into a regular epithelium. This, as the sub-
sequent lnst(jry shows, Ijecomes the wall of the definitive gut, all the
yolk-cells enclosed within this layer being eventually entirely absorbed
(cf. tig. 27). This, in my opinion, corresponds with the la^'er marked
z in fio-. lib. or that marked Dm in tiii's. 11a and 14 in Taf. A'lII of
»Scott's paper (/oc. cit.), although this writer regards the layer as giving
rise to what he calls the " Dottcr-mesodcrrn.'"

J^'ig. 20 shows a transverse or rather obli(jue section through the

ON THE F0R:\[ATI0X OF THE GERMINAL LAYERS TX PETROMYZOX. 139

liead-region of an embryo n little more ndvanced. The neural cord
has made a considerable progress and liy its downward growth has
pressed down the median portion of the gut-roof, /. c. the chorda-
anlage. The latter is formed of a regular row of rather high columnar
cells. Its lateral continuation on each side is reflected upwards and
forms a deep diverticulum of the enteric cavit}'. This forcibly
reminds us of the well known section of Ampliioxm and the sequel
shows that the resemblance is of a deep significance.

In fig. 21 taken from a somewhat advanced embryo, the develop-
ment has advanced considerably. The chorda has now been completely
isolated from its mother-layer, and lies firmly appressed with its upper
margin against the neural cord, in which it causes a slight indentation.
Owing to this isolation, the part of the gut-wall which was before
situated immediately lateral to the chorda-rt??/rt</^, has noAv slipped
itself below the chorda, shutting the latter fr<mi the enteric cavity.
Hypochordal cells Qich) are derived from this part. On each side of
the median line, a conspicuous ridge or fi^ld {x) of the outer wall of
the enteric cavity has raised and pushed itself towards the median
chorda-prominence, thus reducing the previously wide gut-diverticulum
to a mere slit and by that process separating off a triangular m.ass of
cells, the mesoblast (ines.f.).

In fig. 22, which represents a still more advanced stao-e, the
mesoblast mass on each side has been entirely cut off from tlie wall of
the enteric cavity. . The constriction is solely brought about by the
inward growtli of the prominent ridge or fold of the outer wall of the
enteric ca^■ity pre\ iously referred to. Tlie inner end of the ridge strikes
itself against the mesol)lastic layer opposite it, surrounding the chorda.
It does not liowever coalesce with the same, but slips fiu'ther down-
wards beneath tlie chorda and tlie hypochordal cells. At the same
time, the two limbs of the prominent fold become separated : the

140

s. HÂTTA.

florsnl limh or tlio part that originally formed the wall of the giit-
diverticiiluin ber-omes iiicorporatcd in the mesoblastic mass; the ventral
half which was originally turned towards the definitive gnt-cavity,
loosens itself from the dorsal half and passes t(^v>"ards the median line
beneath the chorda and hypochordal cells, nntil it meets and fuses
Avith its fellow of the opposite side to form tlie definitive roof of the
enteric canity.

'i'lie ]^rocess of mesol^last formation in the cephalo-cervical region
as given above, is exactly like what we know to go on in Am.phioxu<^.
Call)erla, Scott, and Shiple)' do not make any mention of such a
primitive mode of the mesoblast formation in Pctromijzon. Ivnpffer's
descriprion of the process in the head region accords well witli mv
own o1)servations, liowever with tliis great difference that according
to him tlie chnrda is cnt off and completed long before the mesoblast
is f rrmod. That such is not the case, T \\[\\e no doubt in my own
mind; my sections speak too plainl}^ for any doul)t. ^ly account also
agrees exactly with tlie results recently inade known by Mitsukuri^ in
Cliel<mia. If one compares my fig. 19 with his fig. 11, one will be
easily corivinced that a certain stretch of epithelium on each side of
the median c\\iW(\'i\' anläge becomes eventually incorporated in the meso-
blasf.

Let us now pass to the truidv and observe the mode of mesoblast
formation in tliat region. Fig. 13 shows a transverse section from
tlie d(>rsal region of an endjryo in which no cephalic protuberance is
seen as yet. In the median line the epiblast shows a thickened
medidlai'v plate {n. ]).) formed of high columnar cells. Immediatelv
beneath, l)ut di.itinctl)^ separate from, tliis plate, there is the chorda-hypo-
blast (ch. //.) forming tlie entire roof of the invaginated tube. Its

1. Fui'ther studies on the formation of the Germinal Layers in ('helonia: The Journal of
the College of Science, Imp. Univ., Japan. Vol. V. p. T.

ON THE FORMATION OF THE OERMTNAT. LAYERS TN PETROMYZON. 141

oonstituent elements have acquired ilie t:ill coliimnm* shape liv repeated
lonoitndinal di\i8ion. Tlie liypohlastic cells iniiiiediatelv outside the
r'li(>rda-h\'pohlast have an elono-ated sliape and are in active nmltiplic;! -
lion as sho\vn hy many karyokinetic figares seen in this ]>arr. Tlie
products of the divisions are accumulated as a triano'ular mass lietween
the epihlast and tlie yolk. This is the jne>iohIa^f (/Hi-'.s.). It is clearly
distinguished from the yolk mass not onlv hv a distinct slit hut also
hy the characters of its coiistituent elements whi('h are smalh^r. liave
their nuclei stained deeper, and are less full of ^•olk granules than volk-
cells. Also karyokinetic figures are often visi])k' in tliis mass, while
they are of rare «x'currence in tlie yolk-cells. Tlius. the mesohlast
arises liere as paired masses liudded out from a few ]iypol)last cells
placed immediately outside tl\e chorda-hypo1)last. This account
agrees suhstantially with that given hy Calberla.' The mesohlast cells
facing the e|)ihl:ist acquire a cohminar shape, arrange themselves more
or less regularly, and l)ecome tlie parietal laver of the mesol)last. In
fig. 13. tliis layer has l)een more or less formed and has l)ecome c()u-
tinuous with tlie external extremity of the chorda-hvpohlnst. The
cells lying helow the parietal .layer are irregularly ari-;inged and are
still having new cells added from tlie liypohlast cells of the aforesaid
part.

Figs. 1 4 and 1 5 are from th(î dors;d region of slight! v older eml)rvos.
Fig. 14 is essentially like fig. 13. \n fig. 15, which represents a sec-
tion more posterior than fig. 14, the mesohlast mass of one side is isolat-
ed, while that of the other side is still continuous with the hy[)oblast. In
fig. 16, the mesol)last masses of both sides are entirelv cut otf from
the hypoblast and have assumed a trianguhu- sha.pe, of which the
inner and outer sides are formed by the parietal, while the ventral side

1. E. Calberla : — Uobei' die Eutwieklunt;- d. McdullarroliTcs ii. d. I'horda dursalis d. 'IV'lcosI ier
u, d. Petromyzonton. INForph. .Tahrb. Bd. III.

142 s. HATTA.

is ocrnpied by the yisceral Liver. There nre a few ee]]s lying" l)etweeii
tlie two Javer.s Avhicli oiia'lit perlin|)s to l)o lookcil ii|)(jii as l)o!oiio-ino- fo
the visceral laver. Tlie chorda -^f/iA////' is now distinct and separated
ivnui llie adjacent livpol^last hy pecnliar s]nndle-sliaped hypochordal
cells which are pro1)al)ly derived from cells originally lying lietween
Ihe chorda-hypoblast and the origin of the niesohlast. In fig. 17
from a still older embryo, the formati(m of the chorda is now complet-
ed, 'fhe hvpochordal cells surround it as before. The gut-hypoblast
lias slipped itself under the chorda and the hypocliordal cells, and
forms the definitive roof of the eriteiic cavity. Fig. 18 shows the
stage in which the medullary cord, the chorda, the hy))ochordal cells
and the mesoblast masses have been completely dilferentiated.

It need scarcelv be pointed out that tlie process of the mesoblast
formation in the trunk is an al)l)re^ iated form of that observed in the
cephal<i-cervical region. ()ne f a-m doç.< not. of course, suddenly pass
into Ihe other, and in the anterior part of the trunk (at just about tlie
place where the head -protuberance is joined to the more j)osterior
o-lobular ])aft) W(^ can see tlie ])hases of gradual transition.

V\<X. 2o is from the moi-e anterior ])art of this region. A' is tlie
f(_)ld tliat starts from the outei- wall of the enteric cavity to push itself
towards the median line. The gut-diverticulum is decidedly shallow-
er than in ha'. 20. Cells seem to l)e budding forth from the outer
extremity of its wall. Fig's. 24 and 25, fi'om an older embryo, are
sections taken more posteriorly. In fig. 24 the more anterior of the
two, the mesoblast mass is being laidded out from each side of the
chovd-d-anhige liut there is now no trace of the alimenta.ry diverticulum.
The hypochordal cells have slip]ied under the chorda. The cells of the
definitive gut-hv]ioblast are still outside the stri[) where the mesoblast
cells have lieen budded out. In lig. 25. they are pushing themselves
below the chorda and hyjioclKn-dal cells to firm the permanent median

ox THE FORMATION OF THE GERMINAL LAA'ERS IN FETROMYZOX. 143

roof of the enteri«- cüNity. ^Fy ol).ser\;!ti()ij.s lead nie to coucliide that
the process of the inesoblast formation begins in the region round the
blastopore and proceeds forwards as the gastral mesobJast. This is
contrary to the conclusion of Knpffer and of Shipley.

('. The lateral and ventral portions of the mesnhla.'^t. In the
ce})ha]o-eervical region which is free from yolk-cells, the lateral and
ventral portions of the mesoblast are Ibrmed Ijy the simple downward
growth of tlte distal or outer extremity of the mesoblastic fold. In the
region of the trunk, tlie process is somewhat moditied on account of
the presence of yolk-cells. The gastral mesoblast in this region
does Jiot extend itself laterally and ventrally as a sohd slieet (jf cells.
The distal border of the gastral mesol)last gives rise to free and
separate cells, which penetrating l)etween tlie \'olk-cells and the epiblast
establish in time a complete layer of a single row of cells.

This has been sufficiently demonstrated by Shipley Clor, oil.) At
the same tune, the jK'i-istomal mesoblast becomes free from the li[)s (»("
the l)lastopor('. and as separate scattered cells pu>h their wav between
the epiblast and the yolk-cells and contrilnite to the forma.tiou of the
mesoblast in the part ^•entral io the Ijlastojxjre. Tin's eircumstauce
may be the reason why the previous investigators haxc, o\ erlooked the
peristomal mesoblast. Thus, at about the stage given in tig. 18, the
whole mesoblast has no connecti()n with any part of the primary lay-
ers. The subse(|uent growth (^f the layei' is solely effected by cell-
multi])lication within the layer itself. The posterior growth of the
mesoblast is liroiight aljout not Ijy any fresh addition from the hypo-
blast or any other struct ure but (jnly 1)\' the extension of its own
territory.

I). TIte metamerie segmentation of the mesohlast. The metameric
seo'mentation of the inesoblast begins first in tlie doi-sal region and
proceeds ijoth bafdvwards and Ibi-wards. When the seginentation has

144 s. HATTA.

been completed the iir.st «ouiite lies just beliind the audhory vesicle
((Uiv. fig. 26).

According to Scott, (/. c, p. 160), the segmentation into meta-
meres precedes in the Selachians the separaticjn of the proto vertebrae
from the lateral plate, but both processes occur simultaneously in
Pclrormjzoit. I learn, however, from my sections that PelromyzoH is
exactly like the Selachians in this respect.

Tlie formation of the germinal layers in l\lromiizon as gi\en
above accords well with tlie general plan of the dcNclopment of these
layers in the A^ertebrata, as shown in Ampliioxus l)y Ilatchek. in Triton
and ll(i7ia by Ü. Hertwig, and in Trlonyx and Clenwiijs ])y Mitsukuri.
The points of agreement and disagreement with previous writers' on
Pelroimizoit as Calberla, Scott, Shipley, and Kupffer liave been
incidentally touched upon, in the course of the present paper and need
not airain be entered int<j in detail. In the main, mv results a urée best
with those of (Adberla.

Zoological Laboratory, Science College, Dec. 1891..

1. I ref>Tet that I have not sceu the work liy Max Schnitze.

ON THE FORMATION OF THE GERMINAI- LAYERS IN PETROMYZON.

Explanation of Figures.

Complete list of reference letters.

(HI. V. iinditorv vesicle.

/;/). l)]astopore.

cli. cliovda.

ch. h. chorda-livpoblast.

e2>. epiblast.

en I. enteric cavity.

hb. liiiid brain.

hch. hypochordal celJy.

Iqy. hypoblast.

it. invaginated tul»'.

//). lateral plate (of mesoblast).

mes. irie.soblast.

uies.y. iiiesoblastic told.

mes. /). peristomal mesoblast.

mes. f>. mesoblast Ic somite.

II. neural cord.

iif). neural or medullary plate.

J). J), e. pleuro-peritoneal cavity.

/'. iiie.s. parietal mesoblast.

/•. mes. visceral mesoblast.

s. segmentation cavity.

vti. somatic mesoblast.

i/f. yolk-ci'IIs.

145

146 s. H ATT A.

Plaie XIII.

Fig. 1. Vortical section tlirongh an egg of the morula-stage. BB x 2 (Zeiss J.

Fig. '2. Sagittal section through an egg of the oldest monila-stage. BB x 2.

Fig. i}. Transverse section through the dorsal region of an embryo in wliicli the

gastrulation is going on. BB x 2.
Fig. 4. Sagittal section of an egg after the completion of gastrulation. BB x 2.
Figs. 5 and (5. Sagittal sections of an embryo in which the peristomal mesoblast is

first seen. BB x 2. Fig. 5, a section through tiie median Ihie ; hg. (5

a section through a plane slightly lateralto the median line.
Fig. 7. Median sagittal section througli the hind end of an embryo far older than

that of the last two figures. BB x 4.
Figs. 8-11. Series of selected transverse sections from an embryo of abotit the same

stage as that of fig. 7. BB x 4. Fig. 11 has been cut through tlie line n b,

fig. 10 through the line c </, fig. 9 through the linc^ cf, and fig. 8 through

the line fi h, in the embryo shown in fig. 12.
ï'ig. 12. Diagram of a median sagittal section through an embryo of about the

same age as that of fig. 5, to show the directions of sections represented

in fiiïs. 8-11.

Plate XIV.

Fig. 18. Transverse section through the dorsal region of an embryo a little older
tluui that represented hi fig. 7.

Figs. 14 and 15. Transverse sections from the dorsal regions <>( a little more ad-
vanced embryo ; fig. 15 is more posterior than fig. 14.

Fig. 10. Transverse section from the dorsal region of a still more advaiiced embryo.

Fig. 17. Transverse section from the dorsal region of a still more advanced embryo.

Fig. 18. Transverse section from the dorsal region of a much further advanced
embryo.

Fig. 19. Transverse section through the anterior part of an embryo in which tlie
head-prominence is ready to protrude.

ox THE FOltMATTOX OF 'I'HE UEP.IMIXAL LAYERS IX PETROMYZOX.

147

Fig8. 2Ü-22. Obli(|Uf]y transvev.sc sectiDiis tlu'on.i^h the cephalo-cervical region,

BB X 4.
Fig. 20. Trausvorse .section oï an onibryo of a little niore atlvauced stage than that

of üg. 19.
Fig. 21. Transverse section from a still i)lder egg.
Fig. 22. Transv(>rse section from a still further advanced embryo.
Figs. 23-20 represent obliquely transverse sections through the plane by which the

cephalic protuberance starts up. ]jB x 4.
Fig. 28. Trans\ crse section of a little older embryo than that of fig. 20.
Figs. 24 and 25. Transverse se(;tions fi-om a still older embryo, fig. 24 being a

more anterior one tlian fig. 25.
Fig. 20. Frontal section througli the cephalo-cervical region of a much further

advanced embryo.
Fig. 27. Sagittal section through an embryo of an advanced stage.

/shikawa..Reproductive Elements,!

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The Disturbance of Isomagnetics
attending the

Mino-Owari Earthquake of 1891,

By
A. Tanakadate, Riéàkuhakushi, F. R. S. E,

Professor of Physics
and

H. Nagaoka, Rié^kushi,

Assist. Professor of Physics.
College of Science, Imperial University.

Plate XV-XXII.

Introduction,

One of the severest earthquakes in the record of this country
devastated the districts alwut Gifu and Nagoya, on the 28th October
1891, of whicli a full account will shortly appear in this Journal.
The Science College of the Imperial University, at tlie request of the
writers, appointed a survey party, consisting of the writers and two
advanced students of physics, Messrs. Ota and Nakamura, for a new
magnetic survey of the district affected. Frequent shocks of varying
intensity occurred for a very long period after the date of the
destructive one in October, and the party did not set out till some
time after these shocks had sensibly ceased, namely, on the 20th
December, returning on the 13th January.

The object in view in having this survey made, was to enable
comparisons to be drawn between its results and those which had

150 A. TANAKADATE AND H. NAGAOKA.

been previously obtained, or which might be obtained, at öome future
time, in order to throw hght if possible, upon the effect of seismic events
upon the magnetic elements of a country, and give some notion con-
cernin<:j: the nature of the subterranean disturbances to which such
events are due. For the purpose of such comparison, it is evident that
a knowledge of the ordinary secular variations of the magnetic elements
of the district is of paramount importance, and this unfortunately, in
the present case, is to a great extent wanting, since systematic magnetic
surveys of this country are of comparatively very recent date.

If we take only the declination, we may go back to the work of
Inö, who made a careful comparison of the compass needle with the
astronomical meridian at various places in the country during his
memorable undertaking of the geodetic survey of Japan, 1800 — 1818.
Since then we have had observations of only a fragmentary nature
until the first systematic survey was carried out by the Geological
Bureau (1880—1885) under the direction of Dr. E. Naumann. Two
observers, Messrs Sekino and Ködari, worked during these years over
different parts of the country, the number of stations being 182 in
all. The results are published in a pamphlet entitled " Die Erschei-
nuno-en des Erdmag'netismus in ihrer iibhäno'is'keit vom Bau der
Erdrinde." Their results were, however, of a provisional character,
in so far that they made but one determination of each element at
every station, and that tlie distribution of their stations was only
alonff certain lines. This necessitated the introduction of corrections
which, as there were no better means, they took from the Tokyo
magnetographs ; while as to isomagnetics much extrapolation had to
be made, notwithstanding the number of stations they took. This was
no fault of the observers, for they had other duties to perform at the
time, and the mode of travellin«]: was not so convenient then as it is now.

During the summer of 1887, Prof. Knott and the present writers

THE DISTURBANX'E OF ISOMAGNETICS.

151

with Mr. Imagawa made a survey, in which they tried to distrihute
the stations as uniformly as they could. They divided themselves
into two parties, indicated as 'south' and 'north,' and as the principal
work was done during the three months, 'Tuly, August, and Septem-
ber, the errors due to the secular and seasonal variations were but small.
The south party made observations of diurnal variations of declination
at every station except three. This, besides giving the mean value of
declination at the place, tells us the nature of the magnetic weather of
the da}'^ on which other magnetic elements were determined. They
made also three or four determinations of the horizontal intensity and
dip, the times of observation being distributed over the day. (For
details of this survey we refer to volume II of this Journal.) Had
we made another series of such observations, we could have allowed
for the secular variation in the results of the present survey, and
should have been able to tell more definitely the kind of disturbance
caused by the earthquake: but, as it is, our results will yet be of service
for determining the secular variation, when, in the future, another survey
shall be made, and then we may be able to draw inferences as to the effect
of the earthcjuake by allowing for the secular variation then ascertained.

There was no particular division of work among the members of
the party ; generally speaking, however, the vibration and deflection
experiments were carried out b}^ the writers and either of the stu-
dents; the dip was determined almost exclusively by the students; and
the declination and time- observations, hoth for the chronometer rate
and for azimuth, were undertaken by the writers.

The stations, as a simple matter of course, were those of the previous
survey in 1887. Although for guidance we had verbal descriptions of
the stations, and the memory of one of the party who had worked on
the previous occasion, the identification of places was not always
easy, as no fiducial m;irk of reference had been left. This was to be

152 A. TANAKADATE AND H. NAGAOKA.

expected, since in the previous survey we had tried to station our-
selves in places which were as far as possible from buildings and hills.
Warned now by this experience, we left a wooden post with the short
inscription, " MtlMMll^,'' îind the date, at each place of observjition,
while further we give (1^1. XV) some topographical details of the locali-
ties, as was done by Lamont, hoping tliereby to save much time and
labour and to give much certainty in identifying the places in future.

The four stations, Nagahama, Obama, Shioya, and Isshiki (Kami-
yashiro, in previous reports), are almost identical with the former
spots, i. e.y are within a few metres. In Nagoya, the Normal School
of the province has since been built on the site of the former station,
and we were obliged to have our new station a little to the east, that
is, in the back part of the recreation ground. Here we made observa-
tions of dip in four places in different quarters of our tent, to see if
the new building, though of wood, had any disturbing effect, and as
the results agreed within reasonable limits, we assumed that it had
not caused any sensible magnetic disturbance. This way of taking
the dip at several points in vicinity was carried out in nearly
all stations where local disturbance was feared. In Shimizu, a coal
depot had been built on the site of our previous station, and the pre-
sent determination was made in a place about 100 metres to tlie
north-west along the shore. Numazu and Hamamatsu are new ad-
ditional stations.

We further took some of the soil from the station and measured
its magnetic permeability. This was done by measuring the magnetic
moment in known field. The field was given ])y a solenoid of 39.1
cm. length, uniformly wound with No. 13 copper wire, to 13.7 turns
per cm. in 6 layers. In order to eliminate the solenoid effect, it was
placed in vertical position, and the magnetometer stood 5.2 cm. west
of the middle point of the solenoid ; there the direction of the field

THE DISTURBANCE OF ISOMAGNETICS. 153

due to the ends of the solenoid is up and down, and consequently
it gives no deflection so long as there is no substance in tlie
solenoid. This position was determined experimental 1}^ by passino- a
strong current through the solenoid. The soil to be experimented
upon was filled into a glass tube which had been tested and f(3und
to be sensibly free from magnetic matter. The inner diameter of this
tube was 1.3 cm. and its length 19.55 cm. When introduced into
the solenoid, its lower end wns brought nearly level with the mao-ne-
tometer, so that only the upper half of the solenoid was used. The
magnetometer deflection was a maximum when the lower end of the
glass tube was slightly below the level of the magnetometer, and in
tili s position the reading was taken. Taking tlie deflection as propor-
tional to the strength of the pole induced by the field, and applying
the correction due to the upper pole, the susceptibility was easil^^
deduced. The only soils that gave any sensible susceptibility were
those of Numazu and Shimizu, two stations which are so far east of
the region under consideration that they do not come into the chart
of isomagnetics at the end of this pnper. The results of the deter-
minations are as follows : —

Soil from Nnmazu Station.

Soil from Shimizu Station.

S^

Ts

k:

C^

A^

K.

26.8

.0199

.00074

26.8

.0059

.00022

85.0

.0817

.00096

85.0

.0238

.00027

127.0

.12GG

.00099

137.0

.0355

.00026

It is remarkable tliat these soils seem to be far from beino-

o

saturated in these fields.

In the following description of stations we give the geological
nature of the soils.*

* We are iiide1»teil to Mr. Y. Kikuchi, Assi-st. Prof, of Geolog-y, for giving this information
about the soils.

154 A. TANAKADATE AND H. NAGAOKA.

Numazu ^ = 35^ 6' ^ = 138° 52'

East bank of Kanögawa, about 150 metres north of the bridge.
Soil : — Pyroxenes, olivine, plagioclase ; derived from basalt.
Magrnetite abundant.

Shimizu if = 35° or2 / = 138° 30:3

100 metres N of coal depot, 15 metres from the sea.

Soil : — l^yroxenes, (juartz ; derived from volcanic rocks.
Magnetite plentiful.

HaGhimanmura f = 34^ 44' I = 137° 45'

About 200 metres N of Hachimau-Yashiro, in tlie farm.

Soil : — Quartz, pyroxenes, apatite, magnetite (very little),
hornblende, tourmaline. Probtibly derived from crystîil-
line rocks.

Nagoya <f = 35° 10.'7, ^ = 13G° 55'

In the east corner of the play ground of the normal school.
Soil : — Pyroxenes, quartz, felspar.

Nagahama ç = 35° 23.'8, / = 13G' loro

Eastern shore of the lake, and former site of castle, edge of
the mulberry farm.

Soil : — Quartz and hornstone pebbles.

Obama <p = 35° 30.'3, / - 135° 44r8

Former site of fortification, south bank of Kumagawa, 70
metres N \Y of Minatsuki Yasliiro.

THE DISTURBÂ^'CE OF ISOMAGNETICS. 155

Soil : — Loam,

Shicya ^ = 36° 18', / = 136° 14'

South shore of the Japan »Sea, 150 metre.s N of the crema-
tion buildina'.

Soil : — Mostly quartz and felspar fragments.

Isshiki if = 34° 30:4, ; =. l3o' 45:3

Middle of salt farjn, former site of fort.
Soil : — Derived from slaty rocks.

Instruments and Method of Observation.

The object of the present survey being to get results closely com-
parable with those obtained in the previous one, we took the set of
instruments that was used by the ' south ' party of 1887, for the sake
of eliminating instrumental peculiarities should there be arjy ; since
the regions to be visited had then been exclusively surveyed by that
party. Of the instrumental constants we give new determinations
somewhat in detail.

Declination Coil. — Its length is 13.3 cm.; breadth, 13.2 cm.;
height, 2.7 cm.; the space unwound in the middle 2.4 cm.: thus
nearly fulfilling the condition for minimizing the error due to ex-
centric position of the magnetometer, in which the ratios of these
dimensions arc 5; 5 : 1 : 1. The coil is wound in two layers, the
under layer with somewhat fine wire to 22.2 turns per cm., and
the upper one with thicker wire to 13.2 turns per cm., making-
in all 35.4 turns. The field at the centre is 6.5 x 35.4-:- 10 -=23 per
ampère, or 0.013 ampère will give .3, the approximate value of H in

156 A. TAXAKADATE AND H. NAGAOKA. "^

those regions, so that a Daniel 1 element prepared in a small bottle
proves suflicient to give the re({iiisite field. Its internal resistance
varies between 20 and 60 ohms., according to the strength of the
solution in the Daniell cell. In order to adjust the strength of the
current for use, a small resistance box consisting of 1, 2, 4, 8, 16, 32
ohms was put in the circuit. This arrangement of resistances gives
the fewest number of plugs with which the resistance can be adjusted,
within one ohm, from 1 up to the total sum of resisümces in the box.

The method of observing the declination was the same as before
described ; that is, by finding the two positions of the coil where its
mao-netic axis coincides with the direction of the earth's field, in one
of which the pivots are reversed after the usual fashion of collimating
telescopes. The mean of the two azimuths is taken to be the
position of the Y'« of the theodolite in magnetic E.-W., corresponding
to the instant at the middle of two observations ; and the difference
as the magnetic collimation of tlie coil. This magnetic collimation
should be constant if the instrument remains perfectly unaltered in
shape. The collimation varied from J' to 1' on different occasions.
We first thought this difference to be personal, but after some num-
ber of triîds, it was found that the same collimation was obtained
by different observers when they worked in close succession, and that
the change was gradual and in the instrument. It might be supposed
that this fluctuation in the collimation is due to variation of the
declination during the course of observation. ]>ut the process of
observation takes only tvvo or three minutes, in no case more than
five minutes, and since the greatest change of declination is only
about two minutes per hour, this change cannot be the cause. The
fluctuation is due probably to temperature variation of the coil.

The position of the circle corresponding to the astronomical
meridian was observed, together with the time; and was calculated,

THE DISTURBANCE OF ISOMAGNETICS. l-')7

by the usual method, from simultaneous equations containing time,
azimuth, and collimation.* For this sort of work the usual method
of forming normal equations by differentiation is altogether super-
fluous, and we follow the abridged method of Cauchy. By this
means we found two azimuths from two sets of observations on
successive nights, when weather permitted ; on other occasions, obser-
vations were made, one in the evening, and one early next morning.
The results of the two determinations usually came out within 10";
this difference is due to two sources, one the error of observation, and
the other the error of graduation. The latter will be eliminated to
a o-reat extent by takino; a number of observations on some circum-
polar stars, and a number of readings of the azimuth circle on dif-
ferent parts of the graduation. For this purpose, we have published
in SugaJcu-butsuri-gakJcwai-h'ji., vol. V., a somewhat extensive table of
azimuths of Polaris, for different hour angles and latitudes, which can
be used for observations of either « or ^^ JJrsœ Minoris for several years
to come. As these two stars differ l^y nearly 6 hours in right ascen-
sion, it will always be possible to take observations which differ by
several minutes of arc in azimuth in course of half an hour.

Magnet. — The magnet is a solid steel bar of nearly square cross
section polished on all sides. Its magnetic moment was found
to have fallen a great deal, and we therefore remagnetized it a few
days before starting, taking care not to reverse the previous magneti-
zation. Placing the magnet on a glass plane, it was found to be
distinctly curved. A lateral face of this magnet, which has better
polish than the others, has a round spot towards the north end, and this
face with the mark always served as the reflecting face in our vibration
experiments. It has remained nearly plane, while the faces perpen-

* See reductiou sheet at the end.

158 A. TANAK ABATE AND H. XAGAOKA.

dicular to it had become slightly curved. This change of shape neces-
sarily altered the moment of inertia of the magnet.

The dimension of the mau^net was therefore redetermined. Tlie
magnet was laid on a thick plane glass plate, and placed in contact
with the o-radaated side of the standard metre scale. This scale is of
brass, constructed by I'reithaupt (Hesse Casse]), and equal to one
metre, at 20" C. The two extreme edges of the magnet were slightly
convex, and were not distinct enouorh to serve as marks for measur-
inof the lenç^th of the mao-net. Two similar, ri^-ht-ano-led, o^lass
prisms were made to touch the fjices of the magnet, perpendicular
to its length. The edge of the prism was well defined, and was
brought in the same plane with that of the metre scale. The readings
of the edges of the prism were taken by means of a micrometer
microscope. The magnet was placed on the glass plate on all its four
faces successively, and the same series of observations repeated for each
position of the magnet. The magnet was then taken off and the
distance between the edges measured under the microscope. This
done, the mao-net was reversed and its lenoth measured no;ain in the
same way as before.

To correct for change of lengtli l^y temperature, two thermometers
were placed beside the magnet, and two laid on the scnie. All these
thermometers were previously compared with the stand:ird thermo-
meter. Temperature readings were taken simultaneously with those
of the micrometer. Generally, the temperature of the mngnet did not
differ by more tlian 0".l from that of the scale.

The following table gives the results of oljservations by ^lessrs.
Ota and iSTakamurii.

THE DISTURBANCE OF ISOMAG NETICS.

159

Observed Length
of Ma<rnet.

7.0053
6.9994
6.9973
6.9990

Position.

Temp.ofScalc.

Temp, of Maf,'.

Length at 0°C

Observer

direct.

16^7

16". 7

7.0010

S.N.

reversed.

16". 8

16". 9

6.9977

)>

direct.

16".3

16".3

6.9956

K.O.

reveröed.

16".6

16".6

6.9973

J)

In the reduction of öcale to 0",C. the expansion coefficient of brass
was assumed to be 0.0000189, and that of steel, 0.0000106. From the
mean of these observations, the length of the magnet is 6.9979 cm.
The leno-th has thus somewhat diminislied since the former deter-

o

mination, by which it was found to be 7.002-1 cm.

The breadth of the magnet was measured at three points; i.e., at
the ends and at the middle. The m;ignet was placed perpendicular
to the metre scale and between the two prisms before mentioned.
The same process of measurement as used for the length, gave 0.8066
cm. at 0"C. for the mean breadth of the bar or its thickness between
the face with the mark, and the one parallel to it. The breadth
of the other faces is of minor importance, and has not been mea-
sured.

In weighing the magnet a Sartorius' balance was used. Care
was taken not to place the magnet near any of the iron used in
various parts of the balance, by not putting it on the scale pan, but
suspending it from this l)y a slender thread, bringing it about 50 cm.
below the balance case and about the same distance above the floor.
The magnet was shielded from air currents by placing it in a nearly
closed glass vessel. The mass of the magnet, as determined by a set
of weights from Sartorius, was 35.0561 grm., and 35.0633 grm. by
the set of weights formerly used. This discrepancy was cleared
up by comparing these weights with those made of quartz by the

160 A. TAXAKADATE AND H. NAGAOKA.

same maker, belonging to the Chemical Laboratory of the College.
The bra88 weights from Sartoriu« were a little heavier, and the old
weights a little lighter. The foll(3wing gives the results of the experi-
ments : —

by Sartorius weights. by old weights.

Observed 35.0561 grm. 35.0683 grm.

Correction + .0038 -.0031

Mass 35.0599 grm. 35.0599 grm.

The mass of the maornet is thus 35.0599 o-rm.

From these measurements of length, breadth, and mass the
moment of inertia of the magnet jibout an axis through its centre of
inertia, and perpendicular to its length, is found to be 144.98 at 0''C.

The moment of inertia was calculated on the supposition that the
magnet is a parallelopiped having the dimensions given above. The
magnet, however, being distinctly curved, it was not sjitisfactory
to use the moment of inertia calculated in the above manner, and
it was therefore determined also experimentally.

This was done in the usual way by comparing the times of
vibration, with and without an additional inertia. In order to eliminate
the diurnal variation of H, the vibrations were repeated several times in
which the inertia rod was alternately on and off. The inertia rod was
a solid C3dinder of brass belonging to a Kew magnetometer (64)
(length = 9.545 cm., diameter = 0.997 cm., mass = 63.071 grm.)
From the comparison of the times of vibration in these two cases,
the moment of inertia Avas found to be 144.995. The following table
gives the results of observations by Mr. Ota : —

THE DISTURBAN'CE OF ISOMAGXETICS. 161

Ohscrved lime of vibration.

Magnet alone.

Teuip.

Magnet with
in3rtia red.

Temp.

2\7276

19M

5\6783

17'M

2 .7244

1G".2

5.G736

15".0

2.7231

14". G

5.6743

15".0

2.7238

14".7

Deflection for complete) , , , , Deflection for comi)letel

11. 1 ■... .. . , , 13'.8

rotation of torsion head. ) rotation of torsion head.

The temperature coefficient for the nionieiit of the mafj-net was
taken from calculation« made on the observation.s at Lsshiki.

Temperature Coefficient of Magnetic Momoit : — In the former
survey, no correction for the difference of temperature in vibration
and deflection experiments was applied in the reduction of the obser-
vations of horizontal intensity. This gives the moment of the
magnet at mean temperature; l:)ut the vahie of the horizontal intensity
is affected inasmuch as the magnetic moment was different in the two
experiments; it will have been less if the temperature was higher in
the vibration than in the deflection experiment, and vice versa.

The determination of the temperature coefficient of a magnet is a
matter of some difficult3\ It is desirable to determine the effect of
temperature on the magnetic moment Ijy placing the magnet in the
same state as in the determination of horizontal intensity. By taking
the number of observations of horizontal intensity at dift'erent hours of
the day, so that there is sufficient difference of temperature during the
experiments, we can obtain data for the calculation of the temperature
coefficient. With this object in view, many observations of the
horizontal intensity were made at Nagoya.

162 A. TAXAKADATE AND H. NAGAOKA.

Tlie magnet, however, showed a sudden decrease of moment at
Nagahamn. It is likely that the temperature coefficient after this fall
of moment \^^as different from that at Xagoya. By using the moments
found at Isshiki, the temperature coefficient was recalculated. For
reducing the results of the former survey, the temperature correction
was calculated from determinations of magnetic moment made at
Miyazaki.

The following empirical formula was used in the calculation,

ilf=il/, + m + a (/-^,) + /> (t-t,y

where M^, is the mean of the moments used, m a small correction to
be applied to il/,,, /,, the mean temperature, iixid a, h the coefficients
to be determined. The above formula was then transformed, for
convenience of calculation, to

where z is any convenient temperature. The following gives the
data and results of calculation from ol^servations made at Xagoya,
Isshiki, and Miyazaki : —

Nagoija.

Magnetic Moment. Temperature.

670.86

16'. 2 3

671.03

16 .12

il/„ = 673.49

671.93

14 .84

m=- 0.02

673.32

11 .13

t,= IVAS

675.06

8.00

a = - 0.546

675.90

7 .53

fc= + 0.0046

676.44

6.49

whence il/=674.3111-.00083(«- 10") + . 0000068(^-107

THE DISTURBANCE OF ISOMAGNETICS. 163

Isskiki.

Magnetic Moment. Temperature.

656.90

11".28

657.55

9.03

657.95

8 .38

M,= 658.19

657.81

8.14

m= - 0.05

660.79

2.07

/,= 7".83

658.17

8 .55

a = - 0.418

656.61

11 .25

b= 0.0057

659.77

3.93

whence il/=657.2G{l-.OOOGO(/-10") + .0000087(/-10'y]

Miyazaki.

Magnetic Moment. Temperature.

436.945

34. G

437.01

34.8

Jl/,=437.45

437.07

34.0

7/1= -0.04

437.19

33.35

t,= 32 '.33

437.58

31.6

«=-0.221

437.95

29.6

h= 0.0076

438.44

28.35

whence il/'=437.96 il-.000586(f-30")+.0Û00174(^-30")-]

Deflection Bod : — The rod is of bra.<^s and about 1 metre long-.
The accompanyuig figures show the rod in liorizontal and vertical
projections, as well as in cross section. V grooves are cut all along
the slender parts a h, a' b' of the rod. AVhen the magnet is laid on V,
the diagonal of the square cross section of the magnet is on a level
with the upper face of the rod. To facilitate the change of position of

164 A. TANAKADATE AND H. NAGAOKA.

natural size.

^ natural size.

Natural Size.

the deflecting magnet and to restore it always to the same place, four
stops a, h, a, h' are rigidly fixed to the rod. These stops are triangular
prisms of brass fitting into the V. Each has a slightly oblique section.
It is so fixed to the rod that tlie magnet comes in contact with the
acute edge of the prism along the diagonal of the square section.
l>efore placing the magnet on the V, the groove was always carefully
swept with a camel's hair brush, so as to make sure of contact, both
along the groove, and against the stop. The magnet was placed in
such a position that the lateral fice with the spot before spoken of
was always turned from the observer. The magnet was slid by the
end of the brush along the groove. In transferring it from one to the
other side of the rod, or in reversing it, care was taken to guard
against change of temperature from handling, by wrapping it in a
piece of folded crape.

The temperature of the rod was read by means of two thermo-
meters (Salleron No. 1386 and No. 15476), each graduated to | of a
degree. They were loosely attached, one to each branch of tlie rod.
One of the thermometers was placed in ft-ont of the observer, and tlie

THÉ DISTURBANCE OF ISOMAGNETICS.

165

other at the Ijack, These tliermometers were compared with the
standard and corrected.

Daring the former survey, the magnet remained straight and came
into good contact with the stops and therefore the distances, i\ and
7*2, of tlie magnet from the magnetometer magnet were known from
the measurements of the distances a a, h h', and the length of the
magnet. 13ut as the magnet had hecome decidedly curved, it would
no longer come into good contact with the stops. Generally, only
one extremity of the diagonal of the square cross-section wîis in con-
tact, while there was a slight gap at the other end. This change of
contact necessitated the redetermination of the distances of the centre of
the magnet in positions a, h, a\ h' , The actual distances of the centre
of the magnet from the magnetometer magnet can only he determined
by placing the magnet in the groove in the same way as in the Jictual
deflection experiments.

The deflection rod was placed on a plane plank, and the lower
side of the metre scale was brouglit in contact with the upper face of
the rod. To guard against any change of position of the metre scale
and the rod, the latter was gently clamped to the plank at its middle,
and any relative moti(}n which might take place between the two
during measurement was noted by a microscope of high magnifying
power. No relative motion of the scale and rod was observed during
the operation. The magnet being placed in the usual way in the
groove, the edge of the magnet adjacent to the stop was sighted, and the,
readings of the scale and micrometer noted in the four positions a, h.
a\ h'. The magnet was then reversed, and the process repeated.
The rod beim?- next reversed, the readinj^'s of the other edo;e of the
magnet were noted in the same position as before. For each reading
of the micrometer, four thermometers were read, two being placed on
the scale and the others close to thé rod. The mean of the observed

166

lengths are.-

A. TANAKADATE AND H. NAGAOKA.

rt ft' = 39.0759 cm. at 0" c.
h h' = G7.0VJ6 cm. ,, „ ,,

The distance between the edges of the magnet was next measured,
both in the direct and in the reversed positions. The mean length
of the magnet from one edge to the other was found equal to 6.9905
cm. at 0'' C'. Thus we have for the distances of the centre of the
mngnet from the magnetometer magnet. —

r, = 30.0196 cm. at 0" C.
r,^23.0332 „ „ „ „

It is to be noticed that the distances of the mao-net frijm the
magnetometer mngnet will be slightly different unless the latter be
accurately centred. Since the centering of the magnetometer magnet
can be easily done with suflicient accurac}^, arid since the correction
te be made from this cause would be ordy of the order of the square
of this error, it was quite negligible in our observations.

The distances of the magnet for two j)ositions, a and b, had to be
corrected for the expansion of the rod as well as fov that of the
magnet. If the expansion coefficient of l)rass be f^-, and that of steel
be /5, it can be easily shown that in place of the fictor (l + 3«t)
(see specimen sheet in tlic former report), used in the calculation of
3I/H in tlie former survey, we must use. —

where / denote the half length of the mag-nets.

Taking «=0.0000189, /5 ==0.0000106, / =7/2, /•, = 30, r,=23,
the value of the coefficient becomes —

1 + 3.08 oi]

THE DISTURBANCE OF ISOMAGXETICS. 167

or its effect is to incrense the temperature coefficient by about 3 per cent.
Correction for the induced Magnetism : — Tlie magnetic moment
arising' from the mao-netization indiicel in the vibration mao-net l)v a
given magnetic field, comparable with that of the earth, was determined
by the magnetometric method. The magnet was placed on the
deflection bar, as in the actual deflection experiment, and was subjected
to various weak fields obtained by means of a solenoid enclosing the
magnet and the bar together. The deflection due to the permanent
magnetism of the magnet was compensated by means of anotlier bar
magnet placed on the other side of the magnetometer on the deflec-
tion bar. A solenoid, 23 cm. in length and 2.() cm. in diameter,
was wound in four layers with fine insulated copper wire, the total
number of turns being 71 per cm. The effect of tlie solenoid alone
was calculated by observing the deflections Avhen the known current
was passed through tlie solenoid, the magnet being ttdcen away.
This deducted from tlie deflection when the magnet was put in, gave
the deflection proportional to the moment induced by the field. For
observing the deflection, a scale cut in mm., was placed at a distance
of 4.2 metres from the magnetometer. By means of a. telescope, the
deflection could be read to the tenth of a scale division. At eacli ob-
servation of deflection, the magnetometer zero was noticed, to guard
against any changes of declination. The fallowing are the results
obtained by Messrs. Ota and Xak:inuu'a : —

Field.

Increment of
moment.

/Tiierea-Je of M\
Vper nuit lifliiy

.157 (direct)

.101

6.43

.306

.201

6.56

.157 (reverse)

.102

6.50

.306 „

.199

Mean.

6.51

6.50

ins .A. TAXAKADATE AND H. XAGAOKA.

Thi:^ result is greater tlian the value used in reducing the
observations of 1.S87. Tlie induction coefficient then used was 3.0,
and was deduced from, the observations made in 1883 on the magnet
from Avhich the present magnet was prepared ]:)y cutting off its end.

AVe tested the result by the ballistic galvanometer method. For
this purpose a coil, into which the magnet fitted almost exactly, was
wound, and its ends Avere led to a low resistance ballistic galvanometer
whicli was 10 metres distant from the coil. The coil lay on a horizon-
tal plane with its axis parallel to the magnetic meridian, and it was
adjusted to this positi(Mi by means of a wooden block. When the coil
was quickly turned round through half a revolution in the liorizontal
plane the ballistic galvanometer gave deflections proportional to the
number of lines of force through the solenoid due to the horizontal
coiu])onent of the earth's field. Now the bar magnet Avas put into the
solenoid, and the experiment repeated; the magnet was introduced
again with its axis reversed, so as to eliminate its direct effect on the
galvanometer. The following is the result of this experiment : —

Moan of 10 readings of galvanometer t-hi-ow without magnet 9.1
„ „ „ „ „ „ -with magnet 125.7
Volume of magnet 4.5 c. cm.

The ratio of the volume included by the solenoid to that of the
magnet is 1.44; whence /^ = ' x ^x 1.44 =^ 0.62, which is greater

than the value obtained by the other method. The difference is such
as might be expected from the difference in Û\c methods, as the first
partly depends upon the distribution of induced magnetism in the
magnet, and the second on the integral effect of induction on the sub-
stance. In applying the correction due to induced magnetism in the
reduction of our o])servations, we have taken the value obtained by
the first experiment, as it refers more direct]}^ to the point in
question.

THE DISTURBANCE OF ISOMAGNETICS.

169

As we suspected that the change in the vahie of n might be due
to the change in the tempering of the magnet, caused probably by the
annual variations of temperature during the years intervenino-, we
made experiments on a similar magnet newly made, lîefore applying
this correction to the previous results. The bar was tempered as hard
as we could make it, and the experiment was performed both in the
unmagnetized and in the magnetized state. In l^oth cases the value
came out in slight excess of the values of the old magnet, contrary to the
above supposition ; we therefore apply the correction to our previous
results. The values of li for 1887 recalculated by applying all the
necessary corrections are found in the appendix.

Zy'if. — This was also the instrument that was used in 1887, i.e.,
iSTo. 88 Dover. Needle No. 2 was always used.

Results of Ihe Survey.

The individual determinations of the mai]fnetic elements are
given in full in the table appended to this paper. We here compare
the mean values with tliose of the previous survey.

DIP

station.

1887

1891-2

DiÊforence.

Numazu
Hamamatsu

48" 29'.0
48" 20'.2

Nagoya

48*' 58'.2

48" 53'.8

-4'.4

Nagahama

49" 17',6

49" 13'.6

-4'.0

Obama

49" 80'.4

49" 23'.5

-6'.9

Shioya

50" 30'.8

50" 25'.1

-5'.7

Isshiki

48" 16'.8

48" 16'.7

-OM

Shimizu

48" 4r.3

48" 37'.1

-4'. 2

170

A. TANAKADATE AND H. NAGAOKA.

DECLINATION

Stalion.

1887

1891-2

Difffvoncc

Numnzii

-

4'^ 19'.45

Hamam:itsii
Nagoya.

4" 18'. 92
4" 38'.r)()

4"

3r.9

+ G'.ij6

Nagaliama

40

45M

4" 42'.81

— 2'. 29

Obama

4"

54'.1

4" 49'.30

-4'.80

Shioya

4^

59'.2

4" ÔG'.lô

-3'.05

Isshiki

4"

21'.S

4" 23'.91

+ 2'.ll

Shiinizu

4"

2'.1

4" 4'.42

+ 2'.31

HORIZONTAL INTENSITY

Numazu

Hainamatsii

— —

Nagoya

.2990.1

Nagahaina

.30039

Obama

.30020

Shioya

.295r)l

Lsshiki

.30210

Shimizii

.30016

.30102

.30141

.30125

+ .00222

.30086

+.00047

.30195

+ .00175

.29668

+ .00117

.30288

+ .00078

.30070

+ .00054

TOTAL INTENS rr Y

Numnzn

■ =

Hainaiiiat.sn

■

Nagoya

.45553

Nagaliamn

.46058

Obama

.46230

Shioya

.46471

lsshiki

.45395

Shimizu

.45467

.45414

.45342

.45823

+ .00270

.46069

+ .00011

.46391

+ .00161

.46562

+ .00091

.45511

+ .00116

.45487

+ .00020

THE DISTURBANCE OF ISOMAGNETICS.

171

The mean values of these elements are the arithmetical mean of
all the observed values, except those for the declination, which are
obtained in a different way. The curves given in PI. XA'Iand XVII
were traced upon tracing cloth, cut out and weighed. From the
ratio of their weights to that of a rectangular piece of the same cloth
covering 24: hours the mean value was easily deduced. This pro-
cedure w^e found more practical than that with Amsler's planimeter.

Through the kindness of Mr. K. Xakamura of the Central
Meteorological Observatory, the pliotographic records of the magnetic
elements at Tokyo during the present survey were placed at our dis-
posal. The inspection of these records showed us that the magnetic
weather during the survey wan generally fair, except on three days
on which we were taking observations at Obama, Shioya, and
Isshiki. The disturbances do not appear to be very serious, and
as our curves of declination obtained in tliose places are not far
from being regular, wc take the mean value without applying any
c jrrection.

During the course of the survey, we felt two earthquakes, one at
Nagoya and the other at Shioya. The former was not very severe
but was accompanied by the usual rumbling, the latter though not ac-
companied by sound was a much stronger one. lîoth of them hap-
pened while we were observing declination, and we took observations
of declination immediately the shock wan over. PI. XYI shows that
the declination suffered a distinct fall at Nagoya but resumed its
regular course after an interval of some minutes. In Shioya the fall
was not so marked as in the case of Xagoya, especially as the shock
happened in that part of the day in which the declination was rapidly
falling. AVhether this is due to chanize in the direction of the earth's
field, or to distortion of azimuth on the part of the instrument, or in
the ground on wliich it stood, we can not tell. In the case of tlie

17â

A. TANAKADATD AXD H. NAGAOKA

Nagoya observations certainly, it is more than can be ascribed to the
displacement of the instrument, as the îjzimuth determined on the two
successive nights, one l^efore and the other after the event, agreed
within 6": on both nights the transits of 7 stars were taken, tlie
reduction sheet of which Ave here append.

Nagoya : December 24.3

Chronometer mean solar, No. 15U4 Negus.
Observer, A. Tanakaclate

Star.

(5

a

Z. D.

Clauip.

T(o1js.)

Rate.

Diur.
Xhev.

Bb.

«-Tù'iii-rl

A.

C.

a Pers

49^29'

li m s
3 16 3G.7fc:

li'lB' N

W

li in s
10 14 2 1.0 J

s
-3.79

-0.03

s
+ 1.15

h m s
6 57 41.61

-0.378

+ 1.53L

£ Eridani

-9'50

3 27 50.73

t4°59' s

W

10 25 31. 4(

-1.98

-O.Oi'

+ 0.55

39.22

+ 0.718

+ i.oir

J» Pers

'12°14'

3 37 51.50

r 4' N

W

10 35 29.31

-0.31

-0.02

+ 1.03

38.49

-o.i6r

+ 1.35]

ÇPers

3r34'

3 47 20.G5

3'36' s

E

10 44 5S.7(

+ 1.18

-0.02

-0.05

39.11

+ 0.073

-1.173

f Pers

35°29

5^1

lir55

3 5157.53

3 57 24.86

4 5 58.63

0^9' N
i9''29' s
76°42' s

E
E
E

10 49 34.8t
L0 55 2.0J

11 3 32.10

+ 1.71
+ 2.8i
+ 1.21

-O.Oi
- 0.02
+ 0.OJ

-0.05
-O.OJ
+ 0.01

38.98
39.9;
38.01

+ 0. I9r.

+ 2.31(

-1.22&
-l.OOi
+ 2.37-1

V Tauri

Gr.(2320).s'.i».

h m

Observations reduced to 8 40. local sidereal time.

"Whence

- 1.379 c + 7.110 a =-- + 5.69

+ 12.90'J c - 1.18G a= - 3.93.

ft - + o'.7G = + ll."3 ; Azimuth reading GT 7' 50"

c= - 0.23 + 11"

Meridian reading G F 7' Gl"

THE DISTUPvBAXCE OF ISOMAGXETICS.

173

Nagoya : December 25/2 Chronometer mean solar, No. 1594 Negus.

Observer, A. Tanakadate

Star.

«Teg-

rPeg-

i Cassiop. ...
A Draco, x.p.

I Andro

oj- Aquil

II H. Ceph...

0

li°38'
23° 0'
61°i2'
G9°55
42''40'
-15° 9'
07° 1 3

a

Z.D.

C'iamp.

li m s
Î2 59 21 Ai

20°33' t

W

23 15 1G.11

12° 1' !-

W

23 20 0.4:

26°31' N

W

23 25 O.OÜ

/■4°52' ^

E

23 32 48.91

7°30' N

E

23 37 6.2(

)0°1S' s

E

23 42 42.01

J2° 3' i^

E

'J'(o)>s.)

!i m s

5 53 53.64

u 9 46.0:1

6 14 29.88
6 19 26.61
6 27 15.90
6 31 32.7:;
G 37 11. OC

Rate.

Diur.
Al^ev.

s
-4.15

-0.02

-1.57

-0.02

-0.81

-0.04

O.OC

+ 0.05

+ 1.2«:

-0.02

+ 1.91

-0.02

+ 2.87

-0.01

Eh.

-0.27
-0.3f'
-0..53

+ 0;4--
-0.73
-0.3C
-LIS

|'/-'r(oornl. )

h m s
3 54 27.74

28.04

28.08

27.07

27.56

28.01

30.02

+ 0.363

+ 0.224
-0.941
+ 2.811
-0.177

+ 0.797

C

+ 1.033
+ 1.08(
+ 2.101
+ 2.91-
-1.36(
-1.03(

-1.37('; -2.581

Observations redaced to 28 25. local sidereal time

AVbenco

+ 4.741 c + 0.459« = 2.8L
+ 9.199 c + 0.396« = L78

a=-- + a30 - 4."5 ;

c = + 0.18

Azimuth reading 61° 7' 50"

+ 5"

Meridian readino- or 7' 55"

A gdîuice al the list of me:in vîïlues will show that tliere is a change
in all the element.s, which are of ditîerent mag-nitude in différent .sta-
tions. In order to make this change more iiitelligible we ha\e drawn
isomagnetic charts of the region, Ijotli from the pre\ious and the present
resnlts. AltlKXigh we !)y no means pretend that the number of stafions
was sufficient to exhibir the actual magnetic condition of the district
with detail, yet we believe tliat these lines are not fir from represent-

174

A. TAXAKADATE AND H. XAGAOKA.

iiig the general c("<in'8e of isomngnetics about those regions. And
tliis was all tliat we could do during the three weeks of winter
vacation whicli we had to spare.

From tlie mean values at the stations, the intermediate values
were interpolated graphically, Ijy assuming tlie proportionality^ of
the space varip.tion of the elements Ijetween two stations, taking
care to interpolate across the isomagnetics as much as possible.
For tlie h(n-izontal intensity and declination, as well as for the total
intensity of the ])revi<3us surve}^, the values obtained at Xagoya were
so much out of the way that we at once perceived a local disturbance.
We therefore excluded Xagoya in the first interpolation, as it would
be wrong to assume proportionality across the space between which
there is a maximum or minimum. When the isomao-netics are
drawn with this exclusion, the course of the curves throws much
light upon the nature of the local disturbance, ^vliich we indicate,
according to our conjecture, by dotted Hnes.

We notice from these cliarts, that tlie general nature of the
change is to make the lines more uniform than they were before.
This is re]narkal)]y shown l)y the observations made in Xagoya
where the l<_)Cul disturbance is very much reduced. Of all the svstems
of isomagnetics, the change for the equal horizontal intensity is the
most striking. r)y the old survey these lines were considerably
deflected from their o'cneral course, f;)rmino- a kind of ridae alorjir
the Mino-Owari plane up to the north c<3ast (^f Japan, l^y the
new survey they are made more uniform, still converging towards
the Wakasa Sea, beyond whicli the above named ridge might be
carried.

xVnother remarkable point is tliat there was a minimum of total
intensity about Xag03^a, which now, Ijy tlie new survey, causes only a
small bend in the line of equal total intensity that passes very near the

THE DISTURBANCE OF I80MAGNETICÖ.

175

place. A\'ith regard to the lines of equal clip the change is least
marked. The bending of these lines towards the south are principally
caused by tlie value of dip at Isshiki. In passing, we may remark
that Isshiki lies very near the now well-known tectonic ridge along
which the geological aspect of the country is suddenly changed.
Another observation at a station somewhere between Tsu and Yokkaichi
mis'lit tell whether this bend exists in the region u'cnerallv, or
whether it is of a more local character and peculiar to the southern
coast.

As was stated in the introduction, we can not ascribe these
changes solely to the effect of the eartlupiake. without thorough
knowledge of the secular vari;iti(jn. JUit the very appearance of these
charts is enough to show that they are anything but usual. The
most important and interesting Cjuestion that naturally arises will be — •
Are these changes of the magnetic state caused suddenly by the eartli-
(|uake, or have they been taking place wholly or partly before
it ? The only results that we can refer t(j for information about the
secular variation, are those of Messrs. Sekino and Kôdari. Mr. Sekino
made 13 observations in various places in the close neighbourhood
of xsTagoya. About Xagahama and Ubama tliere are no observations
until we come to the region near Fukui, ^^■here Mr. Ködari made 7
observations. The values of 11 as obtained by these observers are such
as to change the course of the lines of equal horizontal intensity in those
regions both in the chart for 1<S<S7 and in that given by Dr.
Xaumann in his paper : thus in tlie district near A'agoya 11 is .^9,
while in [)laces near Fukui, which are 2 or 3 degrees north, the values
of 11 a.re nearly .300, sometimes .SO-l. It is difficult to conceive
how Ur. Xaumann obtained his lines of e<|ual horizontal intensity
as given in his chart, unless he excluded either of these sets of observa-
tions.

176 A. TAXAKADATE AXD H. NACIAOKA.

If we take Mr. Sekino'ö results in tlie iiciglibourliood of iNagoy.'i
as consiöteut among" themselves, the course of the hlnes of equal
horizontal iriieusity is very differeut from either of the two systems
we obtained, as shown by dots in Tl. A IX. Considering that tlie course
of these curves will be independent of the instrumental constants,
we feel sure of the fact that these lines have Ijeen underg<3ing
considerable variation during recent years about the Nagoya district.

The fact that the horizontal intensity has suftered the most
disturbance, seems to show that the seat of that disturbance, if it
exist at ah, does not lie at great depth; and this is further confirmed
l)y the smallness of the disturl^ances of all the other elemeüts.
Examining the chart that was provisiorially prepared for the rep(jrt
of the previous surve}^, Avhich is more detailed than the one published,
Ave find the same kind of disturbance near Ilamada — namely
conAcrgence of the lines of equal horizontal intensity towards the
place; and we n(_)w recollect that it was here that the eartlupiake,
wliich was tlie severest one preceding the present, Avas felt in
1872. AVhether this disturljance is due to the change of magnetic
condition of the earth's crust in the vicinity caused by strain, or to the
change in conductivity for earth ciu-rents, or, again, is the result of the
dislocation of the magnetic crust, is more than Ave can decide from
the scanty data Avhich AA^e now possess. These points Avill undoubted-
Iv afford most interesting- subjects of research in the future.

Declination.

station.

Declination.

Date and Hour. (l. m. t.)

Numazu

Placliimaiiniura

near Haniauiatsu

N

agoya

4°

21'

20"

4°

21'

3"

4°

•20'

41"

4°

21'

8"

4=

Ls'

4:V'

4"

19'

41"

4=

19'

31"

4=

18'

40"

4°

19'

52"

4°

15'

54"

4'

17'

39"

4°

IS-

37"

4°

IS'

9"

4^

Is'

19"

4'^

19'

29"

4^

19'

30"

4°

20'

44"

4°

20'

5!"

4^

Is'

49"

4°

J 7'

54"

4°

17'

34"

4°

17'

44"

4°

is'

22"

4=

Is'

21"

4°

19'

4"

4°

is'

57"

4^'

Is-

22"

4°

is'

20"

4°

10'

5S"

4°

16'

57"

r

89'

20"

li ni

December 21 2 34. S p.m.

,, ,, 3 35.9 ,,

„ 8 52.1 „

„ 0 0.2 „

7 41.5 ,,

„ 9 IS.O „

22 7 2.0 a.m.

' ) 1 2 0)

22 4 53.2 p.m.

„ S 51.8 „

„ 10 18.0 „

,, 28 7 55.0 a.m.

„ 10 84.1 „

„ 10 40.0 „

) ) , , X L ÖO.J , ,

,, ,, 0 3.6 p.m.

„ 1 18.1 „

„ ,, 2 86.4 ,,

4 1-^2

„ 6 55.5 „

„ 7 10.9 „

„ 7 87.7 „

„ 9 1.4 „

„ 9 56.8 „

„11 15.9 „

24 0 27.2 a.m.

„ 6 36.8 „

„ 7 84.1 „

„ 9 11.9 „

„ 10 2.3 „

24 7 44.3 p.m.

A. TANAKADA'i'E AND H. XAGAOKA.

Station.

Declination. Date

and Hour. (l. m. t.)

Nagoya

4' 38' 50" Decei

h 111

über 25 0 4.8 a.m.

4' 37' 42"

„ 7 28.6 „

4° 30' 35"

„ 8 28.3 „

4' 36' 47"

„ 9 49.7 „

4° 37' 23"

„ 10 58.6 „

4" 39' 48"

„ 0 2.9 p.m.

4° 40' 44"

„ 0 .54.1 „

4° 40' 18"

„ 1 9.7 I

4" 40' 37"

„ 1 47.7 „

-

4° 40' 18"

„ 2 35.7 „

4° 40' 2"

„ 2 49.1 „

4" 38' 59"

„ 3 45.9 „

4° 37' 58"

„ ^ 31.0 „

4° 38' 4"

„ 5 52.5 „

4° 39' 20"

„ 7 9.9 „

4^ 38' 53"

„ 8 34.3 „

4^ 38' 52"

„ 9 10.8 „

4^ 38' 25"

„ 10 37.3 „

4" 30' 42"

, 26 7 43.6 a.m.

4' 34' 48"

„ 9 4.5 „

4° 34' 50"

„ 9 59.7 „

4° 35' 25"

„ 10 6.7 „

Nagahama

4° 33' 48"

27 11 45.6 a.m.

4° 43' 53"

„ 0 43.3 p.m.

4^ 43' 35"

„ 1 59.7 „

4° 42' 50"

„ 3 16.8 „

4° 43' 23"

„ 3 48.3 „

4° 42' 23"

„ 4 51.3 „

4° 42' 5"

„ 6 35.4 „

4° 41' 33"

„ 7 35.3 „

h in
* Earthquake at 0 59.1 p. m.

DECLINATIOX.

179

Station.

llecliiiatioii.

Date

and Honr. (l. m. t.)

Nagahaina

4''

40'

50"

December

28

h

8

m

27.8 a.m.

4'

40'

24"

,,

))

9

85.8 „

4^

42'

10"

)»

,,

10

52.0 „

4"

48'

28"

)»

,.

U

49.5 .,

4'

41'

1 5"

M

,,

0

15.5 p.m.

4"

45'

(S"

J,

?•

1

9.4 ,.

4^

44'

l.V

!)

,,

o

t).8 „

4^

44'

0"

)>

))

4

15.8 „

4"

48'

?»

>)

5

14.5 „

-

4^

42'

50"

>)

>)

7

8.4 „

4°

42'

85"

)»

M

8

81.3 „

4"

42'

4b"

M

))

8

47.9 „

4'

48'

5"

>>

,,

8

52.2 „

4'

42'

50"

,,

10

89.4 ,.

4^

42'

28"

,,

29

1

l.() a.m.

4-^

42'

8,8"

))

,,

.')

22.0 „

4^

40'

58"

))

,,

8

14.5 „

0])aina

4'

41)'

88"

))

80

0

54.4 a.m.

4°

47'

54"

,,

))

9

24.7 „

4^

48'

89"

)»

)>

10

4.0 „

4°

50'

42"

)>

))

11

48.0 „

r

50'

5"

))

>)

0

20.9 p.m.

4°

50'

5"

))

>)

0

33.4 „

4°

49'

15"

))

>)

1

57.9 „

Shioya

4° 48' 43"

4° 48' 43"

4° 49' 18"

4° 48' 53"

4° 50' 48"

4" 51' 28"

4° 56' 2"

81

(13821

January 8

2 21.1

4 20.6

5 20.2
10 43.4

5 22.3

8 36.1

4 24.3

a.m.

p.m.

180

A. TAXAKADATE AND H. XAGAOKA.

Station.

Declination.

Date

and Hour. (l. m. t.)

Sbioya

4°

55'

49"

January 3

h

4

m

31.7

p.m.

4^'

56'

0"

))

j>

8

4.3

)»

4°

5G'

28"

)j

>)

9

36.6

,,

4^

54'

49"

M

4

2

46.8

a.m.

4°

55'

39"

)>

V

()

20.9

))

4^

.•)4'

41"

J>

))

8

16.0

!>

54'

52"

5J

J)

9

32.3

))

4^

b6'

6"

>>

!>

10

32.6

))

4^

57'

34"

))

»)

11

30.2

J>

4^

57'

44"

>;

))

11

34.1

))

4°

58'

57"

)>

M

0

25.0

p.m.

4^

59'

34"

))

>)

1

30.7

,,

4^

59'

27"

)>

))

2

17.2

))

4°

58'

27"

1)

J)

3

11.7

<>

4=

57'

4"

J?

,,

» >

56.9

,,

4'

56'

22'

,,

>>

5

2s.y

,,

4^

00'

29"

<)

)!

G

12.9

);

4°

56'

33"

J)

,,

7

12.7

) J

4=

55'

24"

5)

J)

9

18.9

,,

4°

54'

47"

>5

5

1

59.5

a.m.

4°

55'

9"

JJ

))

4

46.6

J)

4°

54'

32"

)>

))

7

19.1

>>

4=

56'

27"

n

)>

8

29.9

>>

4°

57'

29"

M

)>

9

24.3

)>

Isshiki

4^^

22'

18"

)>

8

10

24.9

a.m.

4'

28'

1"

5>

,,

11

5.9

)>

4^

24'

32"

)>

))

0

2.8

p.m.

4"=

25'

49"

5)

))

0

56.7

!<

4°

25'

44"

>)

))

1

59.4

))

4'^

24'

58"

)>

jj

2

44.7

))

4°

24'

52"

>>

J 5

3

26.4

>>

DECLINATION.

181

Station.

Declination. Da1

e and Hour. (l. m. t

)

Isshiki

4" 24' 38" Jam

h m

lary 8 4 8.0 p.m.

4° 23' 58"

„ 4 51.4 „

4° 23' 28"

„ 6 53.8 „

4° 24' 7"

„ 7 46.1 „

4° 23' 47"

„ 9 9.0 „

4° 23' 56"

„ 10 54.6 „

.

4° 24' 10"

9 6 39.8 a.m.

4° 23' 13"

7 38.6 „

4" 21' 38"

„ 8 38.6 „

4° 21' 38"

„ 9 31.1 „

4= 21' 30"

„ 10 7.7 „

4° 24' 20"

, ,, 0 4.4 p.m.

4° 25' 55"

„ 1 49.8 „

4' 26' 37"

„ 2 44.7 „

4° 26' 7"

„ 3 34.7 „

4° 25' 15"

„ 4 23.2 „

4° 24' 30"

„ 5 0.3 „

4' 24' 33"

„ 6 31.7 „

4° 23' 25"

M 7 25.8 „

Shimizu

4° 6' 46"

11 1 14.5 p.m.

4' 6' 46"

„ 1 40.1 „

4° 6' 5S"

„ 2 33.5 „

4° 5' 34"

„ 3 37.3 „

4° 4' 56"

„ 4 23.6 „

4° 4' 31"

„ 6 21.6 .,

4° 4' 14"

7 35.5 „

4° 3' 42"

() 00 'S

4° 4' 32"

„ 10 33.5 „

4= 4' 13"

„ 11 27. „

4' 3' 19"

12 8 1.7 a.m.

4° 2' 49"

„ 8 53.1 „

182

A. TAXAKADATE AND H. XAGAOKA.

Station.

Sbiiuizu

Uecl

in a

tion

4"

2'

32"

4^

2'

44"

4°

5'

14"

4^

7'

18"

4^'

7'

12"

4'

7'

23"

4''

7'

19"

4°

7'

12"

4^

7'

14"

4^^

6'

37"

4°

5'

57"

4^

5'

13"

4'

4'

59"

Date and Hour. (l. m. t.)

January 12

111.

9 58.0 a.m

10 46.0

11 48.8

0 53.6 p

1 19.3
1 47.4

. 2 41.0

3 15.2

3 56.4

4 24.4

6 16.1

7 11.5
7 59.0

Dip.

station.

Dip.

Date and Hour. (l. m. t.)

Numazii

4S''

29:4

. .December

21

h III

1 41.8 p.m.

48^

2g:(]

))

8 7.8 „

4b°

8o:tj

-»>

10 2.8 „

48°

29:8

22

8 84.4 a.m.

Hachiman-miira

4S°

20.'()

22

4 24.9 p.m.

near Haniaiuatsu.

4S°

21.1

»»

10 89.1 „

48^

20.'0

28

9 14.4 a.m.

48°

19.'5

Î)

2 8.2 p.m.

48^^

19.'0

M

9 86.8 „

48°

20:7

24

9 48.9 a.m.

Nagoya

4!;'^

1.'4

24

7 55.4 p.m.

48°

58.'8

25

8 9.8 a.m.

48°

50.'5

))

8 19.8 p.m.

48°

54.'5

))

5 10.8 „

48°

49.'5

Î)

7 87.0) „

48°

52:8

)j

8 18.9 „

48°

51.'8

j>

8 52.1 „

48°

51. '9

20

9 88.9 a.m.

Nagabama

4W°

l;r9

27

0 18.7 p.m.

4i/°

l;i'8

J)

4 22 1

41;°

1().'9

28

10 80.0 a.m.

4î;°

16.'9

5)

11 15.2 „

49°

11.7

>)

2 51.8 p.m.

49°

12.'5

))

8 51.1 „

49°

10.-2

about midiiiglit.

Obama

49°

28.'4

20

11 5.0 p.m.

49°

26.^3

80

9 48.9 a.m.

49°

22.7

))

0 8.9 p.m.

49°

22.'8

))

1 18.1 „

49°

28.'2

)>

2 8.0 „

49°

22.T)

)i

4 1.8 „

184

A. TANAKADATE AND H. NAGAOKA.

Station.

Dip.

Date and Honr. (l. m. t.)

Shioya

Isshiki

Sliiini/.a.

50° '2'2:ü
50° 25r5
50' 23:2
50" 26:5
50° 25:8
50° 26:5
50' 26:8
48° I8r8
4.s° 19:0
48° 14:4
48° 18.7
48° 15.'0
48° 16.'5
48' 16.7
48° 14.'8
48° 17:2
48° 17.1
48° 16.'2
48° .37.'4
48° 36.'9
48° 37:8
48° 37.'0
48° 36.'6
48° 37.'4

January

3

11

5

111
().4 p.m.

M

n

6

16.5 „

JJ

4

8

14.2 a.m.

>)

?)

11

7.1 „

?)

5'

2

48.7 p.m.

»)

))

5

58.3 „

)>

5

9

9.7 a.m.

))

,s

10

51.4 „

,,

)'

0

40.7 p.m.

)>

,,

3

2.5 „

>>

>»

4

29.8 „

»»

)J

5

'^0 '>.

>?

M

5

54 2

>>

9

X

23.9 a.m.

)1

)j

9

53.1 „

))

>)

4

12.2 p.m

)>

,,

4

4K.9 „

))

»»

5

31.2 „

January

11

0

.34.(5 p.m.

J»

n

11

;i2 „

>)

12

8

30.9 a.m.

M

,,

10

29 7

,,

)5

1

9.2 p.m.

>>

M

4

43.1 „

Horizontal Force.

station.

Horiz.
Force.

M.

Temp.

Date & Hour, (l.m.t.)

Nninazu

0.80115

()74.67

28^08

D8C. 21

Il m

0 0.7 p.m.

.80078

677.54

14°.65

)t ))

4 45.8 „

.80119

678.00

ir.09

)> ))

8 48.3 „

.80089

679.72

8°. 20

22

7 48.5 a.m.

Hachiman-imn-a . . .

0.80148

678.86

10\78

„ 22

5 57.9 p.m.

near Haniainatsu.

.;50080

679.64

s°.25

)' )'

9 44.0 „

.80116

677.77

ir.69

)> )»

3 41.8 „

.80171

67S.50

6°.85

M )J

10 42.1 „

.80188

677.88

6)'.8l

„ :^4

8 56.8 a.m.

Nagoya

0.80148

()77.85

4'.80

„ ••^4

6 45.0 p.m.

.80107

6)75.60

9M0

„ 25

9 28.2 a.m.

.80186

672.16

16°.48

,, ,,

11 45.0 „

.80119

(570.86

16°.28

»» ))

0 40.7 p.m.

.30160

671.08

16M2

j' >)

1 88.9 „

.8012-2

671.98

14^84

)5 n

2 21.4 „

.80038

<)78.82

11M8

)» »'

4 17.6 „

.80181

675.03

S'.OO

>' '»)

6 47.6 „

.80109

675.90

7^58

>> ,,

10 18.2 „

.80120

(')76.44

6°.49

^21 j

8 45.1 a.m.

Nagaliama

0.80081

(')72.18

l:i°.26

„ '27

1 18.4 p.m.

.80100

674.88

9°.97

)' >)

6 10.2 „

.80065

674.79

8^54

„ 28

9 18.8 a.m.

.80098

672.61

12°.28

)1 M

1 50.0 p.m.

.80078

660.97

8^78

)1 M

4 51. S „

.80091)

6()2.48

8^68

!' )!

10 1.8 „

Ubaina

0.8016()

655.18

16^66

,. 80

1 87.5 p.m.

.30210

658.42

12^08

)? )»

4 59.0 „

.80268

655.42

12°.08

^1 11

9 57.1 „

.80184

654.74

i6°.72

„ 81

9 18.8 a.m.

Öhioya

0.29648

658.96

6M7

Jan. 8

9 4.8 p.m.

.29696

659.01

«°.ll

„ 4

7 11.9 a.m.

18G

A. TANAKADATE AND IT. XAGAOKA.

Station .

Horiz.
Force.

M.

Temp.

Date & Hour, (l.m.t.)

Il in

Sbioya

.29GÜ5

050.58

K/-.99

Jan.

4 0 11.9 p.m.

.29640

050.81

10^79

)j

„ 1 57.0 „

.29650

057.81

r.rji

)j

„ 5 8.4 „

.29070

058.37

r.io

)?

„ 0 40.5 „

.29032

059.02

4°.80

!J

5 8 7.0 a.m-

Isshiki

0.30294

050.90

ir.28

M

« 11 43.5 a.m.

.30200

057.55

9^03

))

„ 1 32.4 p.m.

.30288

057.95

.S^38

))

„ 3 51.7 „

.30281

057.81

SM 4

j^

„ 8 30.9 „

.30283

0(50.79

2^07

>?

„ 7 22.2 a.m.

.30313

058.17

8^55

)!

„ 9 9.5 „

.30284

()5(').(n

1 r.25

5>

„ 2 25.1 p.m.

.30303

059.77

3=.93

,,

„ 7 0.2 „

Sliinn/ii

0.30005

(i53.03

l7^2l

>>

11 2 17.1 „

.3005.S

(;54.35

14\54

>>

„ 3 10.1 „

.30097

059.02

0^24

)?

„ 10 13.0 „

.30072

057.54

9'.08

)J

12 9 10.1 am.

.3004<s

050.02

12^74

)I

„ 11 33.1 „

.3005()

055.00

r/.8o

)5

„ 0 37.5 p.m.

.3007 s

(')5r).4s

ir-50

,,

,. 3 41.9 „

.300S9

05H.29

0^25

>)

„ 5 3.(5 „

Appendix.

Recalculated values of H for 1887-

Station. j

Horiz.
Force.

M. '

reiTip.

Mo.

Date & Hour, (l.m.t.)

Ishibashi

.29184

937.15

2r.oc.

944.37

June 23 6.00 a.m.

Yabuki

.28952

938.60

20°.4

945.-54

„ 25 8.00 „

Matsukawa

.28784

937.78

20°.0

944.60

„ 26 7.00 „

Shiraislii

.28828

936.72

20M

943.58

„ 28 7.30 „

Shiogaiiia

.28754

935.41

22°.6

943.21

„ 29 9.00 „

.28720

933.79

22°.7

941.59

„ 30 6.00 „

Ishinoiiiaki

.28778

936.53

2r.2

943.82

July 1 8.00 „

.28745

937.28

22''. 3

944.. 50

„ „ 5.30 p.m.

Içhinoseki

.28429

936.20

18°.0

942.65

„ 3 7.30 a.m.

Hanamaki

.28030

938.04

18^4

944.28

„ 5 7.30 „

Morioka

.28179

937.26

20°.8

944.39

„ 6 8.00 „

Miyako

.27899

934.70

23°.2

942.76

„ 8 4.00 p.m.

Kuji

.27986

935.56

23^4

943.67

„ 10 4.00 „

Hachinohe

.27688

937.02

22'. 2

944.69

„ 12 8.00 a.m.

GonoliG

.27624

933.75

24°. 3

942.24

„ „ 5.00 p.m.

Nobecbi

.27579

934.52

24M

942.91

„ 13 6.00 „

Aoniori

.27731

935.88

22°.7

943.73

„ 15 8.00 a.m.

Hakodate

.27322

935.75

22°.3

943.19

„ 16 5.00 p.m.

Sapporo

.26768

931.52

25^2

940.29

„ 19 5.30 „

Kiitup

! .26677

933.83

23M

941.82

„ 24 4.30 „

Nemuro

.26047

931.86

2b°.3

941.07

! „ 25 4.00 „

Hirosaki

.27828

932.97

26^3

942.19

! „ 29 4.30 „

Ödate

.27741

935.34

20°. 3

942.24

„ 31 6.00 a.m.

Nöshiro

.27857

930.85

3r.o

941.89

Aug. 1 4.00 p.m.

1

Akita

.28285

932.18

25\2

941.00

1 „ 3 6.15 a.m.

Kariwano

.28231

934.50

26°.4

943.78

„ 4 6.30 „

Yokoto

.28314

932.91

26^4

942.17

„ 5 7.00 „

Iiniai

.28229

931.47

28'.0

941.35

1

„ „ 4.30 p.m

Sbiiiiö

.28530

931.43

27°.4

941.07

„ 7 7.00 p.m

Sakata

.28472

931.94

27^6

941.65

„ 8 7.00 a.m

Yamagata

.28655

932.80

25°.4

941.63

„ 10 7.00 „

188

A. TANAKADATE AND II. XAGAÔKA.

Station.

Horiz.
Force.

M.

Temp.

Mo.

Date & Ilonv. (l.m.t.)

Yoiiezawa

.2888:-)

931.28

30^3 c.

942.04

Aug. 1 1

5.30 p.m.

Oguni

.28756

933.58

2r.8*

941.02

„ 13

7.00 a.m.

Nakajö

.28764

930.23

28°.3

940.20

„ U

7.30 „

Ebisu

.28987

923.57

3Ô".0

936.16

„ 15

noon

Niigata

.28704

928.32

28M

938.19

„ 10

7.30 am.

Kashiwazaki

.28887

927.66

'2\f.l

938.17

„ 17

6.00 „

Sekiyama

.29162

930.36

27M

939.83

„ 19

8.15 „

Ueda

.29636

936.59

21°.8

944.0(5

„ 21

6.00 „

Takanoinacbi

.29531

928.90

26\()

i;38.l9

)) J)

6.00 p.m.

Kofu

.29282

926.19

3b^4

938.40

„ '23

4.30 „

Hara

.30146

929.(59

25\0

938.37

„ 25

6.35 am.

Hakone

.30514

929.1(5

25^4

937.97

)> ;j

5.00 p.m.

Otsu

.29674

927.19

29°.2

937.45

„ 26

5.00 „

Höjö

.29641

927.85

27^3

937.41

28

6.00 a.m

.29632

926.75

29^4

937.10

)) !»

4.00 p.m.

Katsuura

.29622

929.20

25\2

937.95

„ 29

5.30 „

Tögane

.29534

929.22

2z^4

93(5.87

„ 31

6.15 a.m.

Chösbi

.29701

928.60

27^0

938.02

Sept. 1

7.20 „

Kioroslii

.29381

930.4()

23^8

938.69

„ 2

7.00 „

Shimmachi

.29380

929.65

hf.O

935.86

„ 25

5.00 p.m.

Ömiya

.29427

928.92

20M

935.73

„ 26

10.20 am.

Sliimoda

.29992

442.80

2U°.7

June 23

10.30 „

T K ÎS î§ ip

.29992

442.68

2r.2

)> ))

3.13 p.m.

.29967

440.43

2r.8

)) ))

8.21 „

Bhiniizu

.30166

441.45

2r.3

25

afternoon

•^ ?l< J!S viü Jh m

.30022

442.65

2r.4

)) »)

}>

.29971

442.45

26°.0

„ 26

2.10 p.m.

.30016

440.72

25°.2

)) ))

4.31 „

.29906

441.21

25M

„ 27

8.48 a.m.

Nagoya

.29880
.29840

442.17
441.93

26°.9
29".7

„ 30

1) )3

9.02 „
11.44 „

APPEXDJV.

18Ü

station.

j Kc r-iz.
Force.

M.

Tonip. Mo. Dato & Hour, (l.m.t.)

Nagoya (continued)

.299H8

441.37

24°.2 c

June 30

6.26 p.m.

Kamiyashiro

.30234

440.84

24°.7

July 4

8.46 a.m.

-Bumm^^^mm

.30198

441.15

26^3

>' M

11.25 ,.,

.30199

44l.;-!7

24\8

)> M

5.25 p.m

Nagaliama ... ...

.300c-4

439.44

26°.8

„ 6

0.53 ,,

m m m m ë-, m b

.30033

440.31

2&°.7

" •;

6.03 „

.30019

440.07

24°. 9

„ 7

9.02 a.m

Hyögo

.30268

439.85

29=.3

„ 8

2.07 p.m.

Wa^EîniîIPi'Ff^a

.30255

440.36

26^5

4 48

3 >; H/ST®

.30255

441.80

26°.4

„ 9

9.10 a.m,

.3u338

438.85

3r.6

»» 5)

1.20 p.mi.

Tokiishima

.30731

436.82

27 \ 8

, 10

6.51 „

^^Mmm'Émm^^î^

.30515

439.84

27°.3

, 11

9.53 a.m,

.30543

439.55

2 '-'-.2

) >!

0.10 p.m.

Koclii

.31094

435.95

27\9

, 17

0.16 a.m

m ill ^ m %i

.31043

435.9»

2.>°.0

' jj

7.48 „

..3C'842

438.34

;ir.7

J )S

11.55 .,

Minabe

.30437

438.90

31°.6

, 21

9.57 ,.

pfï §iJ ^mu^mi^

.30484

438.51

3r.5

11.30 ,,

mmm^^m

.3048(3

438.12

:i2^8

' )»

2.55 p.ui

.30494

438.74

30^7

) ))

5.56 „

Okayaiiia

.30418

438.16

3r.4

, 26

9.00 a.m

* if M ^" ai m ffi m

.30430

437.71

34^2

1.28 p.m

ffiims

.30446

437.86

33°.0

5.07 „

Hiroshima

.30713

438.02

34M5

, 28

0.41 „

m^HM^m^m^

.30674

437.82

35\2

4 13

WB

.30734

440.34

2.5°.0

, 29

6.32 a.m.

.30688

410.21

2Ô\9

> n

7.35 „

.30650

439.45

29°.9

) >J

8.37 „

.30683

438.43

■34M5

) >j

9.32 „

.30702

437.60

3.5^^'5

> 7J

10.31 ..

190

A. TAXAKADATE AND H. NAGAOKA.

Station.

HiroshmidbicoHtiniied)

AVakwan (Korea). . .
Mêbo (Korea)
Pusan (Korea) . . .

m \u m ^t vi w.

Kurosaki

Shiinokijiina

Fnkuoka

mmfàm^mmmm

Nakatsu

^ miaAt m m

Sagaiiosski

Hichiyamura

Horiz.
Force.

.30697

.30719

.30695

.30716

.30724

.30685

.30711

.30694

.30421

.30463

.30472

.30667

.30592

.30673

.30893

.30915

.30897

.30605

.30514

.31011

.30988

.30986

.30975

.30978

.30983

.31086

.31102

.31146

.313.56

.31334

.31362

M.

437.22

437.38

437.37

437.22

437.74

438.44

438.20

439.22

438.94

438.13

439.33

439.78

438.59

436.76

437.89

436.07

437.44

436.82

437.83

437.40

436.55

435.95

435.53

436.04

437.69

437.24

437.03

436.94

436.74

438.37

436.70

Temp.

Mo.

37^0 c.

36\0

36°.2

35^75

3.5M

3b^3

30°.5

29'-.0

3r.9

32^7

27'.6

2Ô\8

32^8

36M

29°.2

34°.3

2j^2

32^

6

28^

3

30°

5

32°

5

34^

.0

35°

.8

34°

.9

28^

.8

3(?

.7

32^

.5

30^

.4

3r

.4

27^

.8

34^

.0

Date & Hour, (l.m.t.)

July 29 11.35 a.m.
„ „ 0.32 p.m.
,, „ 1.38 ,,

,, ,, Zi.Ö^ ,,

3 32

,, ,, 4.35 ,,

5 32
„ „ 6-^7 „
Aug. 6 10.06 a.m.
„ „ 1.39 p.m.

^' 5 1 9
,, 11 6.34 a.m.
„ „ 11.01 „
„ „ 2.08 p.m.
„ 13 10.56 a.m.
„ „ 2.23 p.m.
„ „ 4.06 „
„ 15 11.24 a.m.
,, ,, 6.40 p.m.
„ 22 7.44 a.m.
„ „ 10.40 „
„ „ 3.24 p.m.

24 1 '^6

4 ^^3

„ 25 8.27 a.m.

„ 28 8.28 „

„ „ 11-10 „

„ „ 3.37 p m.

„ 29 3.49 „

„ 30 8.07 a.m.

., ,. 10.45 „

APPENDIX.

191

Station.

Horiz.
Force.

M. Temp.

Mr

Date & Hour, (l.ji.t.)

Miyazaki

Yatsnshiro

A n m m ïïi m. m i&

Nagasaki

Hagi

Hamada

Matsue ... ,

m m m m m

Iinaicbi

^ m 3 •; s ;t; + T

.31587
.31565
.31552
.31528
.31512
.31518
.315(34
.31569
.31533
.31533
.31588
.31561
.31555
.31521
.31477
.31496
.31458
.31369

.30857
.30902
.30874
.30023
.30022
.30046
.29993
.30014
.29992
.30008
.30019
.30018

437.30
436.67
436.33
436.20
436.27
436.27
436.33
435.40
436.22
436.45
43Ô.31
436.84
437.20
437.70
436.52
436.81
436.42
436.32

436.42
437.03
438.00
438.14
440.06
436.68
437.96
437.91
440.25
438.14
437.49
438.29

3r.4 c

32^9

34^8

34^6

34^8

34".8

34°.0

34°. 5

33°.8

33°.35

33M5

3r.6

29^6

28°. 35

32°.6

3r.8

31=.5

38°.9

32^.2
2;)°.4
26M

26°.0
18^9

3r.2

26^5
26°.0
19^9
24°.2
29°.3
23^7

Sept. 1 8.53 a.m.
9 31
„ „ 10.12 „
,, ,, 10.51 „
„ „ 11.31 „
,, „ 0.11 p.m.

>>

)J

1.30 „

))

n

2.10 „

n

))

•2.50 „

jj

))

3.31 „

>>

)»

4.12 „

7J

))

4.49 „

)9

))

5.29 „

>J

))

6.09 „

»5

()

10.48 a.m.

M

))

4.20 p.m.

))

))

9.33 „

)>

10

9.43 a.m.

M

13

11.20 „

,')

))

0.48 p.m.

))

)5

4.18 „

J)

16

4.32 „

M

17

7.12 a.m.

))

))

11.21 ,,

;j

20

1 .04 p.m.

J>

îj

4.55 „

5>

21

7.00 a.m.

n

22

8.53 „

))

;5

11.40 „

)>

!)

5.14 p.m.

192

A. TAXA -s A DA 'JE AXJ> H. XAUAC»'<.A.

Station.

Horiz.
Force.

M.

Temp.

Mo.

Date

c^- Hour, (l.m.t.)

Kanöniura

.30175

489.14

2r.9 c.

Sept. 25

0.09 p.m.

B^^Pt#^*ftïRlM

.80186

439.31

2ö\9

5J

4.42 „

±m

.30r20

441.22

14°.7

26

7.20 a.m.

Koyamamura

.29971

438.21

24^3

3J

1,51 p.m,

mi^uM^turm

.80971

488.45

21^9

),

■^.07 „

u m

.30008

438.74

2r.3

27

7.51 a.m.

.29962

437.16

28\7

j;

10 26

Maizurn

..30079

438.27

25\3

30

11.49 „

un^mït'hmrxmm

.30108

438.92

2r.5

4.45 p.m.

.30118

440.34

16\8

Oct.

7.07 a.m.

Obama

.30006

438.18

24^7

■2

11.34 „

'j^ mm m m

.30047

438.H2

2r.2

y}

4.83 p.m.

.30006

440.66

16\8

"

8

8.00 a.m.

Shioj^aura

.29536

437.82

26'. 9

4

0.02 p.m.

mmM'hmm-rm

.29566

437.76

26'-.0

>i

4.53 „

.29550

439.00

20\6

5

7.26 a.m.

Nanao

.29398

440.62

16\8

8

9.05 ,.

■bm^nmiMmmw-

.29381

440.18

19\2

y;

0.59 p.m

^IF

.29424

439.26

20\6

5»

73

4.33 „

TökyC ^nV)

.29678

438.13

23\4

Nov

. 8

11.52 a.m.

mmi^mmmm

.29661

4o7.7l

25^4

))

,,

1.39 p.m.

.29659

439.75

17M

5)

j;

4.20 „

„ (E) ,.. ...

.29684

488.99

19^7

))

10

9.29 a.m.

.29644

438.66

22M

!)

);

1.01 p.m.

.29619

440.30

l6^8

>)

35

4.15 „

Optical Note.
K. Takizawa.

If one observes a Xewtoii's ring- apparatus through a thin film ni
mica, several sets of rings are seen in those parts of the field, where
if white light is used, ordinary Xewton's rings are not found. Each
group consists of a middle «lark ring with two concentric white rings
next the dark one, and several colored rings outside and inside.
Besides these prominent gT<3ups, a group of faint rings is observed
inside the first group. All sets are concentric with each other and
the space between any two sets is devoid of rings. The diameters ot
these rings depend on several conditions. The thinner the mica film,
tlie smaller the diameters. The greater the air film of the Xewton's
ring apparatus, the smaller the diameters. The effect of inclining
the film so as to receive the light from the Xewton's ring apparatus
more obliquely is equivalent to using a thinner film. All these
phenomena can be very easily explained by the ordinary elementary
theory of interferrence.

As to the existence of these rings, it is well known that the rings
are invisible in those parts of the field, which correspond to a great
thickness of the air film, because the lio-hts of maximum and minimum
intensities are very nearly equal in their wave-lengths for a given
direction. If we examine a small portion of an <3rdinary Xewton's
ring (which is invisible in white light) by a prism, a large number of
dark bands are seen in its spectrum. If we bring the dark middle
ring of the first prominent, group as seen by a mica film (let us call

104 K. TAKIZAWA.

it the groiij) A) into the centre of the lield by inereayino- the thickness
of the air lihn, so as to form a central dark spot, and examine the
spectrum of a small portion of it by a prisnn we ol)serve a series of
dark bands l)etween which there is a series of curved dark l)ands.
The straight bands are those formed by the mica iihn, and the curved
ones are those formed by the Xewton's ring air film. The dark
central ring of A is formed, because the lights of maximum intensity
throufdi the air film are tlie very ones which are of nn'nimum in-
tensity through the mica film. The re;ison why tlie ))ands are cur\ ed,
is obvious. If we form a white central spot by an approach of A
tow.ard the centre, the straight bands coincide with curved bands, so
that lights wliich are as a, mininumi after interferrence through the
îdr film, are still minimum after the interferrence through the mica.
Hence no change is produced b}' the mica film. After a few colored
ring's, whose fn'mations can be readily understood after the above
explanations of the formations of dnvk and bright rings, there is a
space of uniform illumination. And then a second group that may
be called the group lî, very similar to A is seen. Here again in the
middle dark ring, the liglits of maximum intensities through the air
film are mininumi by the interferrence through the mica. If a
central dark spot Ix' formed of the dark ring and its spectrum
examined, we again see a series of straiglit and cur\ed bands, but this
time tlie munljer of curved bands are twice as many as straight ones.
And one of the straight ones coincides Avith one of the curved ones
in the middle part of the latter. If a central wliite spot formed by
Avhite rings of 15 group be examined, the two curved ones fall neither
on the curNcd dark bands nor on the part just mid-way between
two bands, corresponding to the light of maximum intensity, but
between the two, so that the light of maximum intensity passes
through the mica. AMiate^'er be the order of the group, in the middle

OPTICAL XÖTE.

195

dark riii,U" tlie light of maximum iiiteusity is made minimum by mica
and in the white rings, the straight liands are not in the middle pai-t
between any two dark ciir\ ed bands. Five groups were well obser\ed,
and oToiips of a hiii'her order mio-ht be observed 1)v means of tliinner
mica. It is needless to say that air tihns corresponding to the central
dark Ijands A, !>, C, dkc. are m the ratio of 1, 2, 3, Arc, as is jiroved
bv the fact that the s(|nares of the diameters of the dark rings nre in
tlie same rati<).

The difference of march between once and twice reflected rays
bv the air film corresponding to the middle dark band of A together
with the loss of i. / is precisely eqnal to that introduced Ijy the mica
fihn, as is shown by the fact that the dark band produced by the air
film lies mid- way Ijetween the two bands produced l)y the mica.
Hence the thinner the film, the nearer is the group A to the centre of
the system.

In tlie faint rings, the difference of march intrtxluced by the air
film corresponding to the dark middle ring is greater than that by
the mica film Ijy y /- Hence if we could observe its spectrum, there
would be twice as manv straio-lit bands as curved ones, but I was not
able to observe it on account of faintness.

The effect of inclining the mica fihn so as to recei\'e the rays
more oblicjuely is e(pii\ aient to thinning the film as regards the
difference of march introduced. Hence if the grou[) A is not seen
within the field on account of too ü'reat a thickness of the mica film,
it can be seen if the film is held obli(piely.

The groups are als() well observed l)y refiected liglit from the
front surface of the mica film. It is needless to say that the
appearances are complementary.

196

K. TAKIZAWA.

In conclusion, it may be .stated that the phenomena described
are in no way peculiar to the mica fihn. Any thin film can he used.
The same phenomena 'twere observed hy means of a thin air film
between two achromatic prisms. I'lie observation of course, much
more difficult than Avith a mica film.

Jour. Sc. Coll. Vol, V. PI. XV.

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ERRATA.

By inadvertence of the photographer, the numbering of the figures in
Plate XXVI was put in wrong order.

For " Fig. 1 " read " Fig. 4." For " Fig. 2 " read " Fig. 3."
- For " Fig. 3 " read " Fig. 2." For " Fig. 4 " read " Fig. 1."

Also 11th line from the top, in the Explanation of Plate XXVI, for
" lower " margin read " upper " margin.

Page 243, 7th hne from the bottom, for " Fig 7 " read Fig. 10."
Page 246, 11th line from the botton, for " feldspar" read " feldspar."
Page 256, 13th line from the top, for " wecJienjormig " read " wecTtenförmig ."

The Archaean Formation

of the

Abukuma Plateau.

By

B. Koto, Ph. D., Ri^akuhakiishi.
Professor of Geology, Science College, Imperial University

TI'(7/( Plates XXn-XXVII.

I. Introduction.

T)r. Ediiiüiid Xniiinniiii, in his excellent little work Ucher den
Ban und die Ivntslelntntj der jtijxiN/scJien Inseln^ luis proposed a priinnrv
division of all Japan irito Xortlunai and Southern, by a remarkable,
great, o'eotect(^nic line, a " fos.'^ei maijna^^^ which, as he savs, traverses
tlie \vh(3le breadth ofthe ]\[ain Isl.and, froin the Tacific Ocean to the
Ja])an Sea.

In spite (^f a controversy that has arisen between Dr. Xanniann
and T)r. Ilarada, as to the existence or non-existence of that geolouac
moat, it must nevertheless be admitted that that division is in e\ery
way a most satisfactory one. The South was the cradle of our
civilization, while the Xorth was, down to the middle a<i"es, tlie home
of tlie Ainos. The climate of the St^uth is sunny and mild, iH'inu'
influenced 1)y tlie warm, genial Ivuro-shiwo that washes the Paeitie
coast ; while the Xorth is chilly, for the ])olar cairrent runs close
bv^ tlu' shore.

198 '^- ivOTö.

That geotectonic liiie is :i]so approxiiiiatelv tlie hoiindary of the
vegetation of the nortJi snhtropical zone,^ or the zone of Piiius Tlmnhergli,
and 'rcrmlroemiaccœ are rarely found to the north of that Jiniit.
Thus, from various sides, geologically, historicallv, and olimaticallv, as
well as phytogeographically, this line serve.; as the l)Oundarv for the
great natural division of the Empire.

North dajian hegins from the east side ;)f the Hakoné inonntains,
running straightforward«, in almost meridional direction, towards Hok-
kaido ; and along its Pacific side is to be seen a relic of a once
gigantic Arclisean realm, though disturbed in various ways. Be-
tween this i)re-pala3(3zoic band and the backbone of the island, longi-
tudinal and radial valleys have been scooped out, those of the Abu-
kujui-gawa. Tone gawa, Naka-gawa, and, lastly, of the Kuji-gawa.

The south end of the above-mentioried Arclifean belt lias been
briefly sketched out l^y the ])resent writer in one of his former paj^ers,-
On tJic so-called CrijstaUinc Scliists of ChicJiibu ; the present one is an
instalment of the results accruing from several occasional trips,
since ma.de in the nortiiern prolongation of the same belt, i. r., tlie
Abukuma I'lateau.

II. The Abukuma Plateau.

IVoceeding northwju-ds from Mito, in the province of Hitachi,
once the resident-town of the princes of the same na,me, through Ha-ma-
kaidö or the coast-road of Iwaki, to the mouth of the Abukuma, w^e
there get a tolerably good view of the physical features of the
plateau. The scenery is simple, but grand ; the thickly wooded, pre-
cipitous escarpment faces the sea, with an approximately meridional

1 M. Fesca, Beiträge zur Kenutniss der japanischen Landwirthschait, Allgemeiner Theil,
Karte der Vegetationsgebiete, Tokyo, 1890.

2 This Journal, Vol. II., p. 79.

THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. IQQ

trend. The general aspect vividly reminded me of the Sambagawan
chain of Shikokii, as viewed from the Seto-nchi side. Below, down
the steep dec]i\'ity towards the plain, the precipitous wall is flanked
on the east by tlie palo3ozoic sandstones and clayslates, which grad-
ually submerge themselves under the tertiary and still later forma-
tions; the surface deposits of the lower plain, or rather of a raised beach,
bein«^)' a thick accumulation of D-ranitic blocks and coarse sand.

The superficial covering of diluvial deposits, just referred to,
is mainly coniposed of sand and gravels, with little or no clay that
might keep hold of tlie percolating waters. P)eing of such a coarse
and porous texture, the dry soil is no better than the pumice
ground of Nasu, or the region around Volcano Bay in Hokkaido.
For this reason, we find here many lonely " haras," or prairie-like
ground, 2-4 km. in. I^readth, along the shore, such as the Hara of
Soma, Harano-niachi, and Chilka.

These sterile flats, together with the underlying tertia.ry strata,
terminate al)ruptly at the water's edge, forming jtrccipitous bluffs,
interrupted only by occasioned indentations of alluvial depressions.

The region lying to the west of these grassy deserts is the elevation
of A])ukuma-. It extends over the provinces of Flitachi and Iwaki,
stretchino' north and south for about 150 km. with an averao-e breadth

O a

of 45 km. It is separated from the backbone of Xorth fTapan by the
meridional valleys througli which the rivers Aljukuma and Kuji
make their way ; and its north and south sides are limited by these
streams, which, after making an easterly trend, finally discharge
their waters into the Pacific basin. The generrd outline of the plateau
thus defined is consequently elliptical.

The jjliijsical a.'ipect of the elevation presents a typical -[»liysiog-
noniy (jf a plateau-chai'acter, with the mean height of 4t)lj m. It is a,
broad, gently undulating siuTace, relieved only by some few [)r(jmi-

lient points, the highest Ijeing the Youiogitii-yaiiia (DHo /;/.), with
al)rupt Ijlnifs along' main (h'ainage-ehannels, ii.su;illy in an east a.nd
west course. Tlie hilly tahle-land faces the Pacific sea-l)î)ar(l, as al-
ready iiieiitioned, with a, steep escarpment five to six hundred
niöters down to the plain below. On the west the slops is scarcely
perceptible, and the plateau merges gradually in the fertile valley
of the Abukunia river ; only in a few places is the fall very marked.

The field of my study does not comprise the entire plateau, but
is chiefly confined to that portion between the cities of Taira and
Tanagnru (Plate XXll). As the strutigraphy of the Arcluean for-
mation of this country has not hitlierto been systematically worked
out, it was my desire to know^ sometliing of the sequence of super-
position of the schistose series ; and this point I have always
had in mind during my trips. On the other hand, 1 cared but little
about the topical distril)uti(,)n of s[)ecial grou])s of rocks and tlieir
recipr(jcal iKjundaries, ]ea\ing these details to the mapping geologist,
Mr. Orsuka, who is now prosecuting the field-work of this region.

III. Archaean Geology.

General Statement.

The xlrcluean rocks of the Abukunia plateau, like those of other
parts of the W(jrld, are separable [)rimarily into two main di\i-
sions, viz.: an upper, chiefly schistose, bedded ; and a lower, of the
granitic, dioritic, or syenitic type of iniiieralogic.d composition, but
more or less gneissose in structure. In the (a) upper divisi«3n there
can be recognized at least two leading groups. One of these is de-
veloped in full advantage (3ii the way from T'aira to Takanuki,
throuuii the nariNjw u'oro'es of Gozaisho. The otlier is found in its
typical foi-ni in tlie region lying to the west of tlie f naner, and occurs

THE AKCH.îi:AX FOlîMATlOX OF THE aBUKUMA PLATEAU. gOl

between the base of the riozai^fho rocks and the Laurentian. The
pre.sent paper is tlie fii'st attempt that has ever been made to classify
tlie oldest rocks witliin the confines of the Japanese islands. Beina*
unable to correlate the series of the upper division with anv
with which 1 am ac<piainted in tlie geoloii'y of China and Corea. I
propose now to name the tirst yr(jnp tlie (rozaisJio series,^ the second
the Tahuiuki aeries.' In the (/>) lower division distinctions of stratigra-
pliical sequence and relationship, if any such ever existed, liave
been obliterated. For this assembhiL;-e of rocks, viz., the Icnver division
of the Archaean, the welld^nown term LaurentidHj so named from the
Laurentian Mountains in Canada, and not from the iSt. Lawrence
River, is retained.

The leadinçc divisions of the Arcluean for this rei>"i(jn mav, from
what has been stated, be arranged in the following scheme, according
to the order of whi<'h the o'eolo^'ical features of the region will be
considered in detail : —

iUpiier dirision. "■• (tozaisho series. — (Iluronian?)

Archiüan \ i-i. Takanuki series.

\ljinrer Airh'wn. — Laurentian,

A more comprehensive statement of the results arrived at,
will be given in the summary, after the facts, upon which these
and other generalizations are based, luive been set forth.

IV. Straligraphicai Relations and Slructure^
Sections.

Having sketched briefly the genend aspect of the plateau, and
pointed out my aim, I mav n(jw consider the stratigra[)hical com-
position of the series. It was fjund thtit it is usually disposed in

1 n ^ )% :^ ^ n. m ^ m- - rr ä #. m â m tw ^ m n-

202 ^- i^^OTö.

sharply folded troughs and in extensive, detaclied masses by fre((nent
intrusions of all sorts of younger and older graijites, which tlirough
horizontal pressure assume at times a gneissose structure, 1 have
selected for discussion a number of lines of section where tlie whole
complex so far as represented is favourably exposed. The first of these
sections/ A-l> in Plate XXY, is that lying furthest towards the south,
and is taken along the road that joins the small port of Hirakata
on the east, and Kawakami in the Kuji valley, f:)r a distance of 24 km.
Froju Hirakata to Yamagoya, the road gradually ascends through
paddy-fields. At Yamag(jya, ochry sandstones and grey shales make
their appearance, with tliin sea-ms of lignites wldch seem to be of
tertiary age, as is indicated by the presence of a few fossil plants,^
such as Sequoia Langsdorfii I^i'gt., Juglans nigella Ilr., Jughuis acuiiiinata
Braun., Cdrpuius sp., Acer sp., Vids sp. This is underlaid discordantly
by a black, coarse, massive rock ((t lî) with the aspect of a gal)bro,
covered with red soils and '' niggerheads." As is usually the case,
excellent exposures of this rock were not found, such as to disclose the
relation with the adjacent complex. laidcr the microscope it is a
typically coarse-grained rock, consisting of hornblende and felds[)ar,
with but few remains of augite. The feldspar is grey, contains a
number of rods, arranged in some determined direction, and is said to
be the cause (jf schillerization, as is explained by Prof. Judd. The
light-yellow augite occurs detached within the hornblende in the form
of grjiiiis, as if it had been absijrbcd l)y tlie latter — a phen«jmenon very
comuKjn in gabbro-diorites. Through weitheriug a p )rl;iou of the
feldspar has been removed, and the black components come into relief,
so as to produce almost a slaggy aspect.

1 The positioas of this and other sections are indie ited )jy thick lines, with corresponding
letters on the map, in Plate XXII.

- Explinitory Text (Japanese) to Section KitsuregMwa, pulilished liy the Oeolog-ical Survey
of Japan.

THE ARCHiEAX FORMATION OF THE ABUKUMA PLATEAU. 203

Next ooine.s a peculiai-, ])l:ir'k vock (P Y), of iniissive appearniice
and more or less schistose in structure. It is almost entirely marie
up of large horîiblende-individuals witli some traces of feldspar and
angite. This is evidently part of tlie gabl)ro-diorite, crushed and
compacted to the present form, and accompanied by a new formation of
hornljlende, wliicli occurs in lenticular spaces with tolerably perfect
crystallographic outlines. How this is related to the diorite is as yet
nidviiown to me. If tliis relation were thorougldy examined,
some light might be thrown on the genesis of schistose horn])lende
rocks, whi('li are of wide distril)ution in Aljukuma and elsewhere.

The gabl)ro diorite re-appears from Yöjigata as far as the place
called Hirasode, interrupted at its middle by a- mass of hornblende-
gr:inite. On ascending the Hanatate pass to Saimarii, we see
ao'ain the hornblende-o^ranite, often containino- detached masses of
titanitediornblende schist' and also sniaJ) fragments of it (marked
X in the profile), which produce the appearance of a breccia, cemented
by a granitic material. The whole is frequently traversed ])y yel-
lowish, fine-grained aplitic or pegmatophyritic dykes. The included
ampliibolite dips towards jST. E. with the strike of X. 45° W.

We tlien proceed westward from Saimaru, tlirougli a tliickly
wooded, steep ascent of the Nakayama, pa,ss, locally known as " Xaka-
yama 8anri," and finally come to tlie top, beyond whicli an interest-
ing series of the Archœm schists may be seen. It is mainly an
alternation of (a.) the titanite-hornblende schist, (h) mica-schist, and
(c) gneiss-mica schist ; the second often a,ppro;iching both in its com-
position and appearance to a true quartz-schist in losing either biotite
or muscovite. The whole complex is included by the present writer
under the Tahanuhi series, and considered l)y him to be the oldest

• This is the rock that largely enters iato the cooaposition of the upper horizon of the T.ika-
nuki series.

204

B. KOTO.

moinlicr of the iip|)cr Arolia^nn ^Toiip of Jnpnn. Spocinl fler-icri|itioiis
oC nicse rocks arc ^'iveii in an<~)ther fliaptcr.

As may be cle:ir]v nndcrstood from the profile, the wli(^le of
tlie Takamiki series is piiiclied in between ]iornl)]en(le-g-raMite, and this
iact serves as an examj)]e of iindonbtedJv irrtiptive granite, liaving
literally taken np with it a ]:)art of tlie crust of the eai-th in its bosom,
whatevei- may liave l)een the nature of the irruption, whether passive
or active.

As tlie schists are flaiiked on botli sides 1w irruptive matter, nnd as
all dip at very high angles, we can roughl)^ estimate tlie lireadtli of the
lower meviher of the Takanuki to l)e 5 km. We do not here take into
account the thickness of the upper member, i. e., the titanite-amphi-
bolite (l^ T A), which makes up ordy an insignificant part of the
section.

At Yania-no-Ogawa the gabln'o-diorite (d ]>) again makes its
appearance as a large boss. From here to the village of Knwakami,
we find nothing l)ut the hornlJende-granite (IT U), variously intruded
iiito by the younger biotite-gi-anite (B G) and pegmatopliyritic dykes
(ciy jS^ear the last-mentioned village, the hornl)lende-granite assumes
a gneissose structure (G H G) with the strike north' and south.

The second line of section selected, C-I) in Plate XXA , is one
drawn westwards from Kadöno, 12 km. west of Taira, across the
ridge of Goz;dsho to the west of Taktmuki. This is the best ])rofiIe
one can get of the whole region, -as the line goes approximately across
the strike of the complex, which embraces nearly the complete series
of the Arclitean rocks to be studied, excepting the upper horizon of
the Takanuki series. It is interesting chiefly as showing the strati-
graphic relation in a clear manner in favourable exposures found along
the transverse valley througli which the brawling SauKÎ-gawa makes
its course ; and one of the wavs of coiiimiuiication acr^-^s tlie ])la,teau

THE ARCH^AN FORMATION OF THE ABLTKUMA PLATEAU. 205

itj cut out of the rock.s along tlie Jeft bunk oi' the river. Thi.s road we
call the " Gozaisho döri.''

The l^asal member lies in a S(jmewhat elevated p(jrti(jn of the
plateau (Takaiuiki, 315 m.) on the west, while the eastern half of
the .section comjjrises tlie younger series. The bedding- of the rocks is
always disturbed, and that uf the Gozaish(j complex in ]xirticuLir,
wherever it can l)e detected, as is frequently the case, is vertical.
If we take into consideration, however, the enormous jammino-
together which the rcjcks ha\e undergone, we can easily imagine as a
result the cc^mplete parallelism of all the structural planes, affording
a- false appearance of a continuous section at right angles to the plane
of deposition. Hence it is not safe to infer much from a twenty-three
kilometers section of schists as to the orii>inal ncjrmal thickness. It is
evident, however, that such thickness must have Ijeen enormous. The
right half of the section, grou[)cd t<)gether Ijy me. in one series as the
Gozaisho rocks, seems to be tolei'al)lv free from üreat and iu'e^'ular dis-
turbances, and to l)e all tihcd u[) in xertical [)osition ; and of these
schists I venture to advance figures for the thickness, which is pro-
baljly not less than 10,000 meters.

The thick mass of the (îozaisho schists terminates on the east
near Ivadöno, being there c<jvered by netirly horizontal layers of the
tertiary shales and sandst(jnes. At n«) great distance from this spot,
brown coals are now being profitably worked in the same bed. At
Negishi, a greenish, fine- textured, rather massive sidii.st crops out along
the banks in a vertical posilicjn with a slight incliriation towards the
east. It has the aspect of a clastic rock, and is like a, hardened deposit
of volcanic ashes, with here and there, not infmpiently, wliite, garnet-
bearing quartzite (marked Q m the sectitjn C-D).

This is followed to the west Ijy alterniite bands of green and
white schists, intruded into at times by a hornblende-granite (H (r).

206

JrJ. KUTÖ.

From hear the <if)zai8ho teiu])le, the green Hichists heeoine more fissile,
and intercalated with a hla.ck niica-scliisl^ (mai-ked ^I.) '!''• tlie waii-
ward, in Hie \'iciiiity of tlie disfrict-lxjundar}^ of Uignshi-Sliirakawa
and Kikiita, the green scliists gradually disappear and give place to a
black, crystalline hornblende schist, which occu{)ies the baf>al portion
of the series. The thick complex of schists which we liave liitlierto
traced from Kadono to Ishizumi is \evy persistent and monot<Hious
in character thronijhont.

Havino- briefly considered the lithological succession of the volu-
minous, schistose hornblende rocks, of which the whole gorges and the
solitary ascents of the Gozaisho road are composed, I shall add a,
few words on their nature. These rocks strike north and south
dipping eastwards with verv high angles, and being usually on end,
or vertical. Such being the case, it is iiulte impossible to form a deti-
nite idea as to the sequence (jf sujierposition within short distances ;
but viewing the wliole series at large, I cannot help thinking that
those lying eastwards must be stratigra[)hically younger than the
schists on the west.

The rocks at the west end of the Gozaisho Narrows, consequently
the lowest of the present series, l)ear, as I have already had occasion
to note, the unmistakable physiognomy of a genuine cryst'dline schist.
They are laminated, perfectly fissile, evenly planed; in siiort, they present
none of the signs that would show them to have been formed from
some antecedent rock or rocks through metasomatic and paramorphic
changes so profound, tliat their original ch;u*acteristics would have
been effaced beyond rec(3gniti(3n. Ihit the liiglier we ascend tow^ai-ds
the horizon, tlie rocks become less fissile in siructm-e, appear more
compact and clastic, and eventually pass into a green slate, made up

THE ARCH^AX FORMATIOX OF TITE AEUKUMA PLATEAU. OQJ

apparently of the n.shes nud mud of* volr-niic ejeetameiitn, snh^ie-
qneiitly changed to the pi-e.^ent forni tlironuh varied dviiiuiii«' inctainor-
phisni. It is practically impossible to draw a hard and fast line
between the varieties they present; bnt altogether they form a litli(^logi-
cal continnity and a liarmonions wliole, -altliongh, when their extremes
are C()m])ared side by side, they a])pe.'!r at first siglit to ha\T. notiiing
in common with e;ich other. As I liave elsewhere ])oin1ed
ont, it is very interesting to n(^te that at the higher horizon
are fonnd the light- coloured and rather hard, moi'e comp;ict and
chl(.)ritic varieties, resembling an altered trap ; wlide tlie less liard,
perfectly fissile scliists crop ont at the basal portion, 'five graihial
changes which are observed between mnltifarions varieties a.[)pe!n' to
be due to the opera tioii of some canse, of the natnre of which notlung
certain can be at present made ont.

I am not bold enongh to assert freely that snch l^asal, crystalline
members are the dynanio-metainorpliic prodncts of massive, syein'tic or
dioritic rocks, crushed and remodelled to the present form, as lias been
done by many great anthorities, who claim excessive and pro-
found effects for pressure-metamorphism. For them there are
properly no gneisses and mica- schists, but those derived by pressure
from massive rocks. Taught by the modern school of dislocation -
metamorphism, I was at first misled, while travelling through
the Abnkuma platean, last snmmer, to consider the amphi])ole scliists,
and even the gneisses and mica-schists to be crushed i)rodu(:-ts ; the
first derived from dioritic and syenitic rocks, the second and third
from granites. But gradually I became convinced that at least a part
of tJie Jionibleude scJùsts of tlie Gozaislio series is of prinian/ oriijin
(tliougli its exact mode of formation remains unknown), a)i(l iml a
product of the crusJiiiig e.jfect of a viass-movemi'nt of thr, eartlis crust.

208 ^- ^OT^-

111 tlii.s coiiiiectii^]!, something may conveniently be said on the
mode of foi"mation of those gneisses and schists that come below the
Gozaislio complex', and which are now included ])y me in the Takarniki
scries and the Lavrentinn.

There are in tliis region nnmberless modifications of granites,
syenites as well as gabbros, that are more or less schistose. This once
seemed to me an in\'in('ii:)Ie circnmstantial e\idence of the crushed-rock
origin of schists arid gîieisses, and apparent]}' harmonized well witli all
the facts, then o])served in the field. lUit being nnwilling to C(^me to
a, hasty conclusion. I yisited the plateau again during tlie last Jvaster-
holidays, and tliis time I fonnd some of my former conclusions to be
illusory. There are of cou.rse schistose fjranites, spoken of usual I v,
tliough very impi'operly, as granite-gneiss or gneiss-granite, which are
reall\- coniiected witli tlie massise granite i)f irruptive origin, and tliese
T consider to be of the age of Laurentian. There are again, foriiiiutj
(iHdilier ffroup, ejneisses oiid viira-scliists, a.t one time included by me
witliout distincti(^ii in the same class as the Laiu'entian gneisses. They
are intercalated Ijetween bands of a coarse crystalline limestone, near
Takanuki, for example.

ONci'whelmed by tlic arra,v of facts continually presented to
my eyes (bu'ing field-work, I ])aid little lieed to the interbanded
limestones, wliich besides giye little hopi' of atfonbng fbssili/.rd
remains. Xow, Reyer says, in his TiiC'iretischeii Geolofile, that
carl)onate rocks may reasonably occur inserted I)etween granites
tln'ough interrupted up-welling of a plastic magma by subse-
(|ue,nt pushes (^Nachschuh). Examining closely the mode of occur-
rence of these rocks, [ found the schistose granite to be
really granite (Laurentian) with that special structure, due surely to
the effect of pressure ; while the limestone-bearing gneiss, and the
mica-schist (Takanuki series), both having a distinct parallel arrange-

THE AROHiEAX FORMATIOX OF THE ABUKUMA PLATEAU. 209

ment of component minernls, are, so to spenk, primary r(^ok.s, and shcMild
not be coiifonnded witli tlic foliated granite. The two classes of rocks
are quite distiiict in origin, and are riot issues from a common stock
of ofranite. JSTo o'eolo^-ical continuity is ever found lietween them :
on the contrary, the J/.uu'entian granite and f\\o. foliated granite
intrude into tlie oyerlying, genuine gneisses of the Takaiudvi series,
(lood exposures of their contact will he ire(|uentiy nu'iitioned wlien
ex])Iaining tlie profiles in tlie se(piel.

We now return to tlu' ser-tion wliidi we left at ishi/uini, in
Gozaisho.

UoiDg westwards for a sliort distance, we arrive at the u])])er
edge of the rapids, whence the Sam<;-gawa takes a narrow and swift
course down from tlie plareau to tlie lowland, which lies fniaher
to the east. Here is the boundary of the districts, Higashi-Shirakawa
and Kikuta. As may be clearly understood from the profile (C-D),
tlie al)oye mentioned (rozaisho series are brought to a sudden rlose
by an outcroj) of granites. The massive rocks are dome sha])('(l ;
the peripheral, schistose iiornblende-granite with its enclosed
])atches of the titanite-amphibole schist has a schistose plane which
her!' dips eastwards with higli angles, but on the (^ther side has
westward inclinations. The luicleai- part is a young biotite-granite
(M (r) with mu(di quartz and less mica ; this bard rock hangs oyer
tlie deep gorges of the Same-gawa.

The rock which we first meet with in coming from the east is the
rao-o-ed form of an old hornblende-oTanite, over which the road makes
many crooked turns. It is a schistose modification of that granite.
Examined under the microscope, it is seen to be made up of biotite,
hornblende, plagioclase, orthoclase and, lastly, quartz. J>iotite and

210 f^- KOTÖ.

hoi*iil)](iîi(lo, arc prcNont in ;i1)()!]t (N|!i;i1 (|ii:(iiHHos ; olio-doln so, Imf little;
ciciiv, \\o\\-i\]i\A\QA\ ;i|Kîii^o, nhiiiidüiit, Tho orliiDclnse shows well-
innrked midiihitorv extinct-iojis, niid i>s i-eiii;irkn])lc' for tlie zoiiiiiu'. The
unclear part seemw to differ greatly in clieiuicfd composition, as may l)e
seen from the nsnally dei^omposed state of its interior. It is a svein'tic
or dioritic o-raviite. Misled l;y its rndely r'dnsfose strnctnre, I once
looked upon it as an intermediate stage l)etween syenite and the
n]n[miiM:'K' schists of the ( h )zr!isho series ; and tlien thonght T mio-lit
be aljle to trace the gradu-al passage from one extreme to the other.
During my second visit to this district, however, I discovered a spot
wliere the ampliiholite comes in direct coiitact' with the schistose
granite, tlie former being sliarply cut by the truly irruptive granite
with schistose structure, well exposed on an abraded cliff at the water's
edge. I.ooked at from a distance a mrtrked contrast iri colour and struc-
ture soon suggests something quite lieterogeneous, and on close ex-
a'nin-ition the junction is still very clearly defined, the eft'usive granite
cutting in obliquely, independent (^f the schistose plane of fissile rocks,
while tlie latter is often convulsed and caught up in pockets within
tlie granite. Thi.-;, therefore, affords most conclusive evidence as to
the lieterogeneitv of the adioinino- rocks as re^-ards g-enesis.

îTaving thus traced out, as closely as field conditions vvill allow,
the limiting edges of the granitic boss and tlie (rozaisho series, we ina.y
now proceed to examine the mode of occurrence of the uriderlying
Takanid^i series to the westwards. The last-mentioned complex is
widely separated liy the irruptive mass, of wdiich w^e have already
spoken, from the overlying Gozaisho series, and this holds true of
other sections wdiich we have had occasion to study. The two
series of the Upper Archaean are, therefore, alway:; separated, so far
as I am aware at present, by the interventi(^n of some foreign mass,
usually granite ; and no line of their direct contact has been ever

THE AUOH.-EAX FOKMATKJX OF THE ABUKUMA PLATEAU. ^11

observed either in Aljukauia, or in the upper courtse of the Teiirù-
gawa in tlie province of Shinano.

The Takanuki series is so named fr()ni a villaue in the vicinity
ol which tliat complex is typically dc\elo[>ed. The whole series
is divisible into two parts; the (^/) upper (UTA), embracing»- tlie
multifarious alternations (_)f the titanite-ampliibole scliist and biotite-
gneiss ; the (ß) hnver (L T A), being c(jmposed of a thick mass of
various gneiss-mica schists and gneisses. The occin-rence of the lower
sid)di\ isioii lias 1)een already alluded to in examining the line of secti<)n
of the ^alvayama pass/ where the beds :4and vertical, but dipping
in tlie |)eripheral portions of tlie series towards the middle pcjint,
so as to produce a. f;in-shaped structure of the Mont ]>lanc tvj)e.
Here, however, the schists make a low arch with their mt.in axis in
the riortli-south direction, and the line of section runs olJiquely
across the strike of this doine-sha])ed mass.

The rock iirst met with in coniinu' westwards from the «''ranitic
arc'i of the district boundary is the up[)er member, which forms a
sm-.dl synclinal at Shimo-Matsukawa, and is intruded U]ion by another
boss of hornblende-granite. At Shiino-Matsiikawa we find still the
titanite-ampliiliole schist (U T A) Avith a dip towards the east at low
angles ; and not far from this point, the hnver niember (I> T A)
finally makes its appeurance, keeping the same dip and strike as
the upper. A highly (piart/.ose, brownish, graijulitic gneiss, ac-
Ci)inp;inied Ijy a micaceous schist with plenty of garnet, is found
all along the road for a distaiice of (i km, until we come to the
west of Takanuki. (Jften the whole complex has Ijeen so disturbed,
in \;!rit)us ways and at numerous points, by the intrusion of
biotite-granite, as to mnke <jne alnuj.-it believe the granite to be

1 >Seo p. 203.

212 S- î^oTo.

il normal Dieuiljer of the gneiss-mica .sclii.st, petrographicallv sc^me-
what similar to it. At Kami-Matsukawa, the schists are uearJy
horizontal with a clip towards the north at very low angles, and jn.st
at the west end of Kami-Matsukawa, a, highly coarse-cryst;dline
limestone, about 70 cm. thick, is interhanded Ijetween the grannlitic
schist, having the strike W. 20' X. and dip oO' X. E. At Kamadn
we meet again with the titanite-ainphibole schist, now witli tlie strike

X. 40'^ E. and dip X. ^y.

The line of section, E-F, 1*1. XX^ , fnjni the small hamlet of
Kami-Misaka to Ishikawa, is very similar in general features to
the sections A-B, and C-D. lUit here only a part of the Gozalslm
belt ((t Z) is to be seen, for a distance of not more than ^ km.
ill breadth, flanked on either side l)y a granitic ])(jss. Tiie lower
memljer of the Takanulcl series is concealed from \ iew in the present
line of section, (jwing prolja1)!y to a greit dislocation line, whose
s(jiilh('i'n prolongation at the we.>t of Takanuki may be traced in (he
last protile ; and this fault has probably brought the u[)per member in
direct contact with tiie granite.

As may be seen from Eig. 8, PI. XXIV, the above mentioned
small l)clt of the ( ruzaisho rocks at the east end of the protile, is pinch-
ed iu between granites \\ (r and 11 (r, ;(nd conseijueutly tlie mode of
arrangement is very much disturbed. Xear a small water-mill at Xaka-
Misaka, a tourmaline-ljeai'iug hornblende- sali te sehi>^l (h) of a rather
black, massive a])pearance seems to abut against the neck of an
amj)hiltole-picrite (d), but the exact relation between them c<.)uld not be
made out. Tha peridolite is, ou theea.st, in direct contact with thehorn-
bleiide-<irainte, which is itself more or less u'ueissose in structure
{gn) near the line of contact. The peridotite is followed, to the west,
by I)auds of spotted chlorite-schist, alternating with a garnet-
chloritoid-quartz schist (c), said to contain the unique mineral

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 21^

piedmontite/ which is of very wide distribution elsewhere in Japan,
especially in the island of Shikokii. The chlorite schists are followed
by another bind of platy epidote-amphibole slate (a), which is tilted up
in vertical position like the overlying- rocks, and is partly corrucrated
at its junction with the biotite-granite (1) (1), indicating that the latter
has broken through the former, and brought it to its present form.

Beyond the small ridge of Komori-zuka" (574 m.), the horn-
blende-granite makes its appearance, often interrupted by a later
eruption of the bifjtite-granite, and nlso by the formation of aplitic
dykes (d). Between Jùmoji and Kodaira, we meet with a detached
mass of the titanite-amphibolite (U T A) of tolerably large dimen-
sions. This soon gives way to the hornblende-granite, which is more
or less gneissose (G H 11), with the plane of schistosity inclining towards
the east, having just the same dip as the last-mentioned patches of
amphibole schist. At Xakagura the granite has acquired a peculiar
hal^itus (Xakagura type), owing to the predominance of somewhat
large grains of quartz, which gives to the rock a blotchy appeaî'ance.
Farther to the west the line of contact of the granite with schists is
observed, in which the irruptive nature of the former through schists
is clearly marked. Not far from the line of contact, a dyke (L P) of
about 2 m. thickness is found in a vertical cleft. The material of the
dyke is of a dark-greyish colour with brown spots. Microscopic
analysis, the details of which are given in a separate section, proves it
to be an augite-dioritic lamprophyre.

From Xakagura to »Söri, through Otsuka and Nakata, the rocks
exposed are multifarious alternations of thin bands of titanite-amphi-
bole schists, and gneiss-mica schists (U T A). Of the amphibole

1 This journal, Some Occurroia'^: of Piedmontite in Jdpan, Vol. I. p. 303; also On the so-call-
ed Crystalline Schists in Chichibu, Vol. II. p. 93.

2 See the line of section E-F, PI. XXV.

214 ^- i^öTö.

rocks WC h;ive to mention as cliief varieties the tifanite-hiofite amphibo-
lite,, tifanite-salite ampliiholite, titanite-feldspar amphiholite, and lastly,
hiotite-amphihole gneiss. Those of the second category show the follow-
ing modifications, viz., i\\Q gneiss -mica sdiist, two-mica schist, garnet-biotite
schist, and also hornbleiide-biotite schist. The whole complex has been
variously faulted in parallel lines, giving rise to a so-called stair-case
structure ; at otlier times horizontal pressure seems to have produced a
compressed arch. Again, in one case at Otsuka, a mass of hornblende-
granite must have been squeezed along a fault-line, considerably disturb-
ing the adjacent rock on the east, while on the other side schists seem to
overlie conformably the granitic basis (Fig. 7, PI. XXIA). This
boss affords an excellent example of the schistosity of a granite. The
peripheral portion is highly gneissose in structure in conformation to
the surrounding rock, and little by little it gradually passes to a
iionnal granular variety at the centre. How such structure has
been brought about is not an easy question to answer. It may
perliaps be the result of a crushing during epigenetic movement of
rocks, or may have been produced, as Rej^er^ assumes, during up-
welling of a semi-fluid magma by constant pushes (Nachscliub), by
lateral compressions.

The amphibolites and gneisses, lying to the east of the last-
mentioned irruptive mass, have acquired a specially great fissility,
cleaving easily into a papery slab ; and owing to its loose texture, the
rock falls into a bluish-black, ashy-looking powder on weathered surfaces.

The structure of the Archsean belt at this part is undoubtedly a
very complicated one, as has been suggested in the foregoing
lines. The rocks are mostly brought to a vertical position, or dip at
angles rarely less than 80°, with the strike of X. 20° W. Considering
their present position as a result of pressure, the recurrence of

1 loc. cit.

THE ARCHJÎAN FORMATION OF THE ABUKUMA PLATEAU. 215

the same zone in the section is by no means nîiIikeJv. But, makinof
a small deduction for the breadth of the eruptive rock and a cor-
rection for the dip, we can estimate the probable thickness of the
formation, and this was found to be 5^ km. for the upper horizon
of the Takanuki series.

At Sôri, wliere the road bifurcates, one leading to Tnkanuki,
the other to Kodaira, an important tectonic line was accidentally
discovered. Here an insignificant isoclinal valley comes from the east,
through the villages of Kodaira and Nakagura, along whicli tlie present
line of section was drawn. A precipitous wrdl on both sides of the
rivulet is wholly composed of alternate bands of the titanite-amphibole
schist and the two-mica schist ; all of them dip westwards at very
blüh angfles with the strike north and south. A ridg-e alono- the

Co o o

west side of the valley, forming a naked whitish precipice, at once
gives information of its being composed of a granitic material, con-
trasting greatly in colour and habitus with the black, schistose
rock of tlie opposite side (Fig. H, Fl. XXIII)'.

If we adopt the view of the excessive effect of dislocation -met a-
morphism, and in accordance with it attribute the formation of banded
gneis.-es and amphibolites to the crushing of dioritic and graniti«" rock
by strong pressure, it is not yet easy to conceive of such sudden changes
of structure at so short a distance. Therefore, I examined very
closely the spot where possibly the line of junction of the schists and
granite might occur high up on the cliff ; and in doing so, I found
actually the place where two geological bodies of entirely different
origin come in direct contact, side by side, having nothing in
common either in appearance or structure. The granite is the
hornblende-bearing variety with an imperfectly schistose structure and
its plane of schistosity inclining towards the west ; and the streaky,

1 In Fig. 11, PI. XXIII, X:ikagura valley is erroneously spelled as Naqura.

216 ß- KOTÖ.

lenticular nodules of a dioritic habitus, j)i-oduced by differential move-
ment of a granitic magma,, di[) with tlieir longer axis towards the
same point. The complex of amj)hib()lite and mica-schist has also
th(i dip in the same direction ; but it is sharply separated from the
other by a nearly perpendicular line of fault, which seems to continue
soutiiwards for a lono- distance, with the bearin«- J^. 30 E.

From what has been said, it is evident that the granite and
schists are geologically different bodies, brought to their present situa-
tion side by side by a down-thrust of the schistose member, and they
are hi/ no means structural phases of one irruptive stock. Although the
secti(jn now examined seems at first sight (piite insignificant, and
to have no bearing of geological importance, nevertheless -it has
been of great use to me, by showing clearly the two sets of rocks
to be of heterogeneous origin. Some gneisses and amphibolites
approach in tlieir outward aspect to the schistose modification of
granites, aiid ('ouibunding tliem together is very liable to occur during
field-work. Tiiis in itself is to a certain extent reascjnably allow-
able, but it would be a gross error to c<)nsider tlie two kinds of rocks as
different phases of primarily only one species of rock. For some distance
to the west, tlie same schistose granite with streaky nodules continues
to ap[)ear along the road as far a.-s Ishikawa, where it gradually passes
into a, norma] granular variety, containing likewise blackish nodules of
a nu)re or less dioritic habitus. We see here a number of reddish,
fine-grained pegmatophyre dykes (d), lainning N, 80° F. with N. \V. dip.

The last line of secticm ((x-11) that will be examined is drawn from
Ishikawa, to Shimo-Ivawabe on the right bank of the Abukuma-gawa.
This traverses the region from S. E. to N. W., and stretches for
about 6 km. Tlie chief interest attaching to tlie present section is not,
however, in the bedded formations of the series, but in the irruptive
rocks wliich, mixing with e;ich otlier, cause a very complicated tectonic

THE ARCHtEAX FORMATIOX OF THE ABUKUMA PLATEAU. 217

couditioii. The effusive rock that cijiiies here into consideration is
mainly granite. It is to be separated into an older, hornblende-bearinü'
(H Gr), and a younger, bi otite- bearing (B (jt) variety. They intermingle
with one another in such a confused manner as to try the patience of even
careful observers ; and many have entirely ignored the heterogeneous
origin of the two kinds of massive rock (Fig. 1, Plate XXIV).

On the way from Ishikawa to a small height where the road as-
cends towards Shibukawa, we meet with the continuation of the
granite-mass, already referred to in tlie preceding profile. In one spot
a mass of di(jritic habitus occurs of tolerably large dimensions. Ex-
amined under the microscope, it is found to be mainly composed of feld-
spar and needle-shaped liornblende, with a little l)iotite and orthoclase.
Macroscopically it appr<jaches in its external aspect to the so-called
" needle-diorite " (marked x in rhe sectit)u). Mot fir from this point,
another exposure of a siiiula,r kind makes its appearance in a road-
cutting. Blackish dioritic patches of various sizes are enclosed in
normal hornl)lende-granite, as if a dioritic scum had floated on a
granitic paste, and then Ijeen torn asunder by s(jme movement in the
semi-fluid mass. Tlie patches seem to have been once a part of the
same granitic magma, slightly different in chemical composition (Fig.
8, PI. XXIII). These should not be confounded with the caught- up
fi-agments of amphibolite in hornblende-granite, or the hornblende-
granite in biotite-granite, as the encl(3sed and enclosing rocks
in the latter tw(j cases differ both in age and composition, and the
patches have angular outlines.

Just on the to]) of the hill, two large dykes (d) traverse the granite
in the E.-W. direction. The material of the dykes is a pegmatic minei-al
aggregate with large orthoclase crystals twinned on the Baveno type.
Large, opaque biotite, smoky quartz, and muscovite are other ingredients
of this aggregate. A dull, brownish beryl is said to have been found in it.

21g B. KOTO.

The rest of the region represented in the section is entirely
composed of old nnd yoiing granites, which appear successively
aloner the lines of fault after the manner of ruin-marbles. Sometimes
aplitic dykes traverse the rocks irrespective of the nature of the granite.
The hornblende-granite assumes at times a gneissose structure in the
usual manner, as is indicated on the west end of the section G-H. From
Nakano a quartz-bearing augite-andesite covers the eroded edge of the
underlying rock. Near Shimo- Kawabe (z), fieiuiis of a hornblende-biotite
gneiss of the lower member of the Takanuki series are enclosed within
the mass of hornblende-biotite granite of schistose structure, and the
whole is traversed by coarse pegmatic dykes (Fig. 5, Plate XXIV).

V. Petrography of the Laurentian Rocks.

Generally speaking, the granites of the extensive region of Abu-
kuma may be classed in two categories ; the first group is a rather
greyish-looking, medium-grained variety, in whi(;h the long prisms of
hornblende (8mm.), and the broad, hexagonal scales of biotite could be
easily recognized within the admixture of the white ingredients of the
rock. It is hornblende-granite. To the second group belong those
common, coarse-granular granites of a lighter colour, built up of
a flesh-coloured orthoclase, and a grey, vitreous, allotriomorphic quartz,
mixed with black mica.

These two groups differ greatly in many respects ; the grey rock
contains, as is usually the case, more of the plagioclases when com-
pared with the light-coloured rock, although none of the last named
rock is free from the presence of the striped feldspars. The most
common rock of this region is undoubtedly hor)il)lende-granite. It
may be seen all over the district wherever exposures of granites are to be

THE AROH^AX FORMATION OF THE AEUKUMA PLATEAU. 919

foiHifl, being often cut sharply hy wide dykes of tlie hiotite-amnite in
a most confused manner, as is represented in Fif»". 1, l^Jate XX TV.
Therefore the biotite-gTanite must he of later age than the hornhlende-
bearing variety. When sneli dykes of the younger granite appear
repeatedly within a short distance it is often not easy to say wliich is
the foreign mass and which the intruded (^ne. It is not necessary
to point out the localities of snch oceurrences, as these perplexing
cases are inevitablv met witli durinii- field-work.

A. Amphibole-Granites and Biolite-Graniles.

The dominant rock of tlie region, the .aniphibole-granite, has, as is
already stated, a very uniform composition which varies only thrt^ugh
local fluctuations in (piantit^y of the several ingredients. AM the rocks
included under the ]n'esent group contain, therefore, quartz, orthoelasr,
inin'ocline, vJdfu'nda.^e, aiiiphiJtoh'^ hiotife, titanitt', apatite, zircon, and
opaque iron ores. To tliese may be added the usual, secondary
accessories, such as rpidote, chlorite, mu^covite. and iron-filanci'.

!)ef()]-e we enter into the detailed description of the individual
occurrences of granites, it may be well to speak of the minerals which
enter into the composition of the rocks. Although their properties
do not ditfer in essential points from those of other granites, still it
seems well to give here some consideration to ~them as likely to
prove of some use for the mapping geologists of onr Geological Survey.

The feldspars are of three varieties, viz., orthoclase, microcline,
and plagioclase. The secondary muscovite, resulting from decomposi-
tion, is common to all of them ; while epidote is very rarely observed,
indicating that the plagioclase is of an acid nature, and consequently
poor in lime. In regard to dimensions, there occur large and
small individuîds which, althouofh belong-in"- to the same o-eneration,

220 ^- KOTö.

still differ a great deal in size even in the same rock. The orthoelase
and plarrioclase are both of large dimensions; l)nt the latter is the smaller
of the two feldspars, and is idifnnorphic in comparison with the mono-
symmetric variety, while tlie microcline is nsually of an allotriomor-
phic form, and is the latest in its formation' nnd the smallest in its size.
Tlie orllioclase is a greyish-white form, nsnally devoid of well-
defined crystallographic outlines ; it becomes flesh-red in slightly
decomposed specimens. In the field, observers might l)e easily
misled to consider such aii orthoclase to be a different varietv, and
consequently would make a quite distinct type by calling the
rock which r-ontains it a red granite in contradistinction to the
common grey one ; but in truth both form one and the same mas.s.
As already stated, orthoclase is proportionally large in its size,
and usuîdly encloses a more or less idiom« )r])hic plagioclase ; l)ut
I have never met with the reverse case. l^•of. Rosenbusch
re]ieatedly asserts naost definitely, in his Mihroshtpische Physio-
(jraphie^ that thr dogma, that orthoclase falls mare ecmhj a victim
to décompositions than the other fellspars, is not based on ascertained
fact ; I)ut I geueralJy find ortlioclases to l)e more dirty, crooked,
and fissured, and much more decomposed than the other members of
the same gron.p, when viewed side by side in the same portion of a
slice. The mouocliuic feldspar is fissured iii all directions, and is also
characterized b}'- tlie presence of abundant liquid-inclusions and other
foreign interpositions, especially when compared with the other feld-
spars. AVell-defined crystals of a brown mica, indeterminable, co-
lourless needles looking like sillimanite, crystalloids of hornblende,

1 Dr. Dathe, when speaking of the ordei* of crystallization of feldspars in the liiotite-g-neiss

of the Eulengebirge, says: scheint nach meinen BeoJjachtmitji'n an.du-'<i'n und r.ahlreicheii anderen

Gneissen und Oramiliten der Plaf/ioklas zuerxt, hierauf Mikrohlin, arldiess/icli Mikroperthit und
Orthokla'f sich ausuenchieden rm haben. Jahrb. d. königl. preuss. geol. Landesaustalt für 1888. p.
318. Whether the same rule may or may not be applied to an inidonlitedly irniptivo granite
like ours, is a question for the future.

THE AKCH^AX FORMATION OF THE ABUKUMA PLATEAU. 221

zonall y coii«ti'iicted zircon, red iiv^n-glance, opaque iron ore.s, and
Jastly, apatite, are the usual guests. A bluish schiller, so common
in the Swedish granites, is not observed.

In tlie advanced stage of decomposition, the mineral resolves itself
into pseudophitic scales, w^hose tufts and aggregates are arranged
at right angles, and also parallel, to the c-axis. The epidoti-
zation seems here to ha\^e not taken place ; l)ut if it does occur amidst
the feldspar-substance, then the material for its formation must ha\e
been surely derived fr<^m the hornblende, evidence in favour of this
being easily deduced from the presence of ropy strings ol chloritic
matter directly connected witli the degenerating amphibole, and pene-
trated and inhltrated in the feldspar along the clefts in the latter.
The polarization -colour is languid and dull, ranging from yelloAvish-
brown to grey ; a prominent feature is, h(jwever, the presence of the
parallel-fibrous structure in crystals in a somewhat advanced stage
of decomposition.

The niicroclliie is present only in small quantities. Macroscopicallv,
it can not be distinguished from orthoclase, as tlieir colours and lus-
tres are quite similar. I nder the microscope the microcline nature can
only be recognized bv its characteristic reticulated or cross-hatching
structure. The mi lierai is usually of a small, irregular form, filling
the interstices of other components, and also forming the outer z(jne of
the plagioclase or orth(j(jlase. It is generally fresh, and pellucid, and is
poor in liquid-inclusions ; consequently it can not be supposed to ha\e
been produced by the albitization of orthoclase, like that of granite in
Socotra.^ It Ijelongs to the latest generation. At times larger grains
seem to occur in the rock-mass, and these are partly changed
i]]to muscovite. Small microcline forms, too-ether with o-rains of
quartz, a. part of the njck, producing thereby what is called the

1 A Sauer, Zeitschr. d. deutschen geol. Oeaellschaft, vol. XL. p. i4ü.

222 .^- ^oTô.

mortur structure, or with tlie same, a micropeginatic iiitei-growth;
the latter is developed on the peripheral zones of other feldspars, and
the stalks of quartz, which are disposed in regular orders, stand at
riofht ano'les to the faces of the enclosed mineral.

The plagiüclase occurs in the fresh state. Muscovite is always
the mineral formed from it when weatliered ; no epidote crystal is
ever found, a fact which speaks in favour of the acid character of
the feldspar, of its Ijeing poor in lime. The quantity of the
plagioclase is greater than that of the orthoclase and microcline. The
plagioclase is usually of a large size, and with quartz it forms a part of
the micropegmatic intergrowth. The twinning lamellation is distinct-
ly developed, yet not so finely as in that of the laljradorite series.
Well-outlined clinopinacoids are seldom met with, as is usually the
case in such granular rocks as granites, and the direction of extinction
could be very nirely measured on that face ; some opportunities were,
however, afforded for such an observation, and it then extinguished
light in tlie positive sense at about S'' with the edge I'/M. ^Sections with
twinning lamellations make an extinction-angle of 4^ symmetrically
with reference to the trace of the twinning sutures. From this it
may be inferred that the plagioclase in question is of an oligoclastic
nature, or else is closely allied to oligoclase, perhaps albite. A feature
which characterizes this variety of feldspar is its zonal structure, and the
presence of this feldspar could be readily recognized by the zoning, even
without examiiiing for the existence of the polysynthetic twinning.
The plagioclase is rich in crystalloids of hornblende, lamelke of biotite,
round-edged needles of apatite, and nearly ellipsoidal crystals of zircon.

J'he quartz occurs, as is usually the case in granites, in a xenomor-
phic, angular form. Macroscopically it seems n(jt to have taken an
inqxjrtant part in the composition of the rock, and in some varieties it
sinks into so small a quantity as to give to the specimen the appearance

THE ARCHAWX FORMATION OF THE ABUKUMA PLATEAU. 223

of a dioritic s^^enite. The colour of the quartz is light -grey, and
when it contains abiindancs of liqnid-inchisioiis, and also stiff,
bent, and broken trichites, it becomes more or less bluish in shade.
These trichitic bodies come indifferently in quartzes of the granite-
rnass, and in the veinlets which variously traverse the quartz.

Notwithstanding the scarcity of macroscopic quartz, it is largely
represented microscopically in the rock, and forms, with micro-
cline or pJauiijclase, a fine aofOTeo-ate between the larwr individuals <jf
feldspar, hence the mortar-structure of Tornebohm. Under polar-
ized light between cr<jssed Niçois, the variously coloured mosaics consist
partly of the intergrowth of quartz and feldspar, radially arranged
aroiuid the feldspar individuals, forming a sort of delicate fringe,
and bringing about, in consequence, the pegmato|>hyritic' structm'e.
The latter is chiefly confined to the fine-grained variety, containing
richly zoned feldspar, but having oidy a small quantity of quartz-grains.
The liquid-inclusions are abundantly present, forming band-like
swarms, and the quartz containing them resembles a smoky quartz.
Hexagonal scales of biotite and rounded ci-ystals of zircon are also
found as enclosures. Undulatory extinctions and optically diverse
orientation of the grains show the rock to have iDeen sul)jected to great
pressure. It is remarkable to observe that where (piartz is plentiful,
striated feldspars with the cross-hatchini' structure are very abundant.

Accessory components are apatite, zircon, and iron ores including
magnetite, titanic iron, and ])yrites.

The apatite occurs as enclosures, especially in biotite and horn-
blende, and also as an independent ingredient. In the normal mass of
granite it is comparatively rare, but in the caught-up granite, as well as
in those of the contact cheeks of lamprophyres, tufts of apatite- needles

1 Lossen, Vergleichende Studien lieber die Gesteine des S2}iemont!< und des Boseul/erf/s bei St.
Wendel u. verivandte Kruptirtypen aus der Zeit des llothlie<ienden. Jalirl). d. k()m;^l. preusa. geol.
Landesanstalt für 188'J. p. 270.

224

B. KOTO.

pierce tliroiigh the «ubstaiice of hornblende and l^iotite, and partictdarly
int(j the grains of feldspar enclosed by the horn 1>J en de of the canght-up
granite. The larger apatite-crystals are short and broad, and have
the edges rounded perhaps by corrosive action; the delicate, slender
needles of the same mineral are sharply bounded by plane surfaces with,
h(3wever, broken terminations, and are comparatively small in
size. At tirst sio-ht, both modifications seem not to be of identical
chemical composition ; Ijut their respective cross -section s give the cine
to their true nature, and show that both modifications belong to the
same mineral. The well-defined needles may l}e of a later origin, and
their formation may be ascribed to the effect of a contact metamorphism.
The magnetite is sparingly present in the normal rocks, but in the
schistose variety and also in the patches caught up by biotite-granite,
it is plentiful, occin-ring either in a drop-like form, or in well-
finislied octahedrons. Iron j)ijrites forms part of clumps of magnetite,
and performs the function of the interstitial mass between the granitic
components, just like the mesostasis of younger eruptives. The octahe-
drons of magnetite are specially abundant within somewhat
decomposed feldspars. Also in a partly altered hornblende, the same
mineral fills up the clefts of cleavage-planes, appearing just like
numerous black needles, all regularly arranged ])arallel with the princi-
pal axis of the crystal. As a whole, the formation of the magnetite
seems to stand in intimate connection with the act of inetamorphism.
The deposit of magnetite in the valley of Clu'ika makes its appearance
between the diatrophic clefts of a strongly compressed gneissose ov
schistose hornblende-granite, and the source of the iron ore must be
souo"ht for as similar to that of the formation of magnetite in the <''ra-
nite, already referred to. iSometimes blood- red tablets of iron -glance
are interposed in feldspars with a certain definite arrangement, appear-
ing in black needles and in minute red scales, producing thereby the

THE AROH^.AX FORMATTOX OF THE ABUKUMA PLATEAU. 225

so-called aveiitiirine lustre. The other h'on ore, titanic irou, seems
to occur in the rcick, since its presence is iiidiciiterl l)y the formation of
leucoxene borders around the cores of ii'on. Zircon in grains and also in
crystals of the usual habitus is chiefly enclosed in the h«^rnl)lende and
biotife.

Spliene is onlv observed in the hornblende-^'raiu'te from Xakii-
tani, near Tshikawa. Fluorite^ so common in granites, is wanting.

'ilie colonrcd componrnts are represerited by biotite, as well as by
hornlilende, and form the characteristic, dark, confusedly fibrous
parts and flecks in the gneissose variety of the granites. In the striped
granite the mica and hornl)lende have the same orientation, and the
base of the l^iotite and tlie c-axis of the hornblende lie in the same
plane. Conseqnently the maximum-extinr-tion happens simultaneous-
ly in the two minerals, along the plane of the pressure-cleavage of the
rock. Apatite, zircon, and magnetite are fonnd as enclosures in the
mica, while the hornblende contains besides them crystals of biotite,
showing that the latter is of earlier generation than the former.
The usual chloritic material, resulting from the decomposition of horn-
blende is absent in the cases hitherto observed. The amphiljole is
remarkablv fresh. The biotite is, however, partially altered into green
lamelleö by the lileaching of that mineral, these changed bands being
interlaced with the fresh foliœ of the biorite ; and the secondary
epidote is aJso fonnd in the 1)leached parts.

The biotite is by i'nv the most common of the two minerals; the
absolute quantity of it may, howeNcr, fluctuate within wide range.
The pleochroic halos usually so common in it are discerned here only
in a few cases. Observed from the base, it is of a dark-brown shade,
and sometimes so interisely coloured as to give the appearance of an
opaque body. It may at once be conjectured that the mineral is highly
ferriferous, and the result of an analysis made l)y Mr. Hida, of the

226 ^- ^*^Tö.

Geoldo'ioa] Survey, establishes its cheinic:i] nature to he that of
l('l)id()}iie](iiie. The followiuo- percentages are those found ])\ liini: —

SiO. 8(). 60

ALO, 17- 05

FeO 'A\. 29

CaO trace

]\rcrO 10. 86

MnA 0- 70

Na^O 5. :\9

KgO 8. 49

99. 88

The angle of the optic axis is so small as to give almost an mn-
axial stanroseo]iic figiu-e.

The hornblende-granite occurs very frequeritly in detached
masses and in leriticular forms, enclosed within hioiite-grauite of
a more acid composition and of a mnch later origin. The biotite in
such a cauqlU-up (jraiiite ])resents a peculisir feature not observed in
tlie normal minei-al. The mica is liere devoid of its crvstallographic
outlines, and the deep brown lamella^ of this mineral with ditferent
optical orientations are heaped together around the larger one. Thns
the microscopic scales of the biotite with its marginal ragged structure
possess the same habitus as tliose found nniversally in contact rocks,
and in many of the crystalline schists. Tlu^ larger crystals are inter-
lard, ed Avith needles of apatite.

Tlie hornhlende has a bluish-green colour. The extinction-direc-
tion varies within wide latitudes, and gives nsually larger angles than
those ^of common species. The most distirictive feature of the horn-
blende of our granite is, however, its weak pleochroism, comparatively
faint polarization-colours, contrary to our expectation from its deep
bottle-green colour. The degree of absorption is normal : c]>6>a.

THE ARCH.EAX FOEMATIOX OF THE ABUKUMA PLATEAU.

227

Thu habitus of tlie cry.sfal.s of liornbleiide Is to be slender, flat and
prismatic, witli the faces oP, y. V ^. , l\x P^ , and cc P ; twins are
rave (Fig. 2, Plate XXIII.) The anahtical result o1)tained bv Mv.
hlida is as follows : —

^^O, 45. ,vi

AI2O3 4. 47

FeO 8. U'J

CaO -20. 40

MgO ]]. 44

Na/ ) . . '2_ .ji)

I^.^ 0. 79

99. S9

The hornlilende in tlie caught-up granite, like the biotite, shows
some peculiar marks entirely f(jreign to the c(3mmon species. Fn
tlie jnassive granite the crystals of hornblende are usually idiomorphic
while in the caught-up nx-k they are of large dimensions and at the
same time allotriomorphic. Inlaying just the same role as the aiiiiite in
diabases in the formation of the so-called diabasic structure. In the
normal sequence, as is well known from the (observation of Prof.
Posenbusch, the crysfalli/Jng-out of the ferro-mngnesian bisiUcates
precedes that of the feldspar-group. Here we ha\e some excepti<jual
cases, probably arising frcjni the unconnnon circumstances under
which the njck reached the solid state. A S(jme\\diat large, all(jtrio-
morphic hcjrnblende of a dark-green colour, encloses, as it were, the
interstitial mass of basaltic rock, a nuniber of equally allotri(jmorphic
crystals of phigioclase oriented in diverse directions (Fiu-. 7^ pj;,te
XXITL). The plagioclase ( ? alhite) in tiie present case presents
tlie habitus of albite with corroded appearance, occurring usually in
large «piantities in the schistose amphib(jle rocks. The h(n-nblende
occurs in the form of an opliitic plate with uniform extinction over

228

B. KOTO.

coii«icler;ible area«, just as the augite behaves within the mass of
diabasic components. This ophitic plate of hornblende is well ex-
emplified in the rock from Kawa-na, near the railway station at
Iwanuma. The hornblende, like the biotite occurring associaled with
the amphibole, is variously pierced through by needles of apatite.

The t-ranite-hornblende inmiediately in ccjntact with the dyke (^f
lamprophyre presents quite an anomalous feature, one de\ iating from
the habitus hithert«) described, tlie clianges in it having Ijceu, l)ey(jnd
all doubt, bnxight about by metaniorphism in c«jming in (-(jntact with
the intruding dyke. Here the amphibole is smaller in size tlian the
otlier \ariety, and moreover, occurs in rather flat prisms more bluish
than oreen in colour, while its cleavage-sutures are numerous and
distinct. Its crystals show diverse intergrow^th among themselves, a
phenomenon rarely obser\ed in other cases ; tlie outlines of larger
individuals are irregular and alh^triomorphic. In short, the Avhole
appearance is an exact ctjpy of that commonly met with in some
uranular crvstalline schists.

O 'J

Among the secondary minerals may be mentioned epidute in
s«jniewhat large grains with its customary intense pleochroism ;
it is found usually enclosed within a more or less Ijleached lùotite
or in hornblende.

The material for the formation of epidote must have been
directly derived from the enchasing minerals. Feldspars, though
showing an advanced stage of decomposition, are free from it, indica-
ting that tlie feldspars in the present case are p<Jor in lime. When
epidote occm-s, it can only ha that the material for it has flowed to
that spot by capillary action through the cleavage-plane, or through
some fissure admitting free passage. The epidote-grains thus originated
are connected by strings of chhjritic materials to the mother-mineral,
which is, as is already stated, either biotite or hornblende. The

THE ARCHiEAX FORMATTO\ OF THE AP.ÜKÜMA PT.ATEAU. 229

end-prodnct of decomposition of the last two rainevnls. the hornhlende
and hiotite, are chloritic substances, while feldspars end in ])rodncin,£r
a psendophitic mineral, which is regularly arranged with reference
to the crystallographic outlines of the original mineral. This is
rendered visihle in the aggregate colours of polarization by the
peculiar position of foliar of a rauscovite-looking mineral.

B. Structural varieties of Granites.

a) Amphibole -Granite.

The prinr-ipal rock of the Ahukuma plateau, the amphibole-
granité, shows a great uniformity in its mineralogical composition, but
varies locally in texture with the relative proportions of the composing-
minerals. It consists essentially of (piartz, orthoclase, plagioclase,
microcline, hornl)lende, and biotite, the last two ingredients being
present nearly in equal quantities. As all granites contain some
quantities of micas, I suggest fn- the present rock the name horn-
blende-granite. The accessories are a])atite, zirc(^n, and iron ores ;
titanite is rare. Tlie general coloiu* is rather greyish ; but the
weathered rock is of a rosy tint, owing to the oxidation of iron in
the feldspars, and may 1)e disringuislied as the pink-granite.'

For the type of this amphil^ole-granite may be taken that
from (Jomi-sawa, in the Jigoku-road, 1^ ri south-east of Ono-shin-
machi. It is coarse crystalline, and its crystals of horrdilende attain a
length of more than 1 cm. The deep oily-brown biotite is entirely or
partially enclosed by the am]ihibole ; consequently the former precedes
the latter in the act of cryst:dlization. The ])ellucid needles of
ayxitite acciunulate at tlie margin of these coloured minerals. Plagio-
clase, with a rather coarse twinning-lamellation, is idiomorphic in

1 See ante p. 220.

230 B- f^^^*™

conipju'ison with orthoclase, and is nsnally enclosed by the letter.
The twiniiiiig Ininellte extingnisli liu'ht :it small ntigles, consetinently
it iiia\' he fairly supposed th;it the miner:il belongs to the oligoclase-
andesine series. The broad zoning is distinct, with differentiated
exti notion-angles. The orthoclase is anguLir and :dlot)-ioinorphic, its
apparent regidnr outlines having resulted from the (hsposition of the
adjnee)it ervstals, especially of plagioclase. (^a;n'tz fills up tlie in-
terstitial sj^aces left by other minerals, contains crystalloids of feldspars,
and a])])ears somewhat fihrillaled, especially when viewed l)y po]arizc(l
light lietween crossed Xicols. The quartz is comparati\ely free from
hc[uid irjcl usions.

As to the structure I have to say only a few words. One
of the most interesting features of our granite is the presence
of the allotriomorphic feldspar, playing just the same role as the
granite-(piartz; that is to say, the interstitial masses of a non-striated
feldspar Ijetween a more or less well-finished ]^lagioclase. These
masses show a homogeneous extinction over a Avide area, like the
vitreous base of many neoA'olcanic rocks ; and though occurring in
detached spaces, they ]iossess surely an optical continuity. Where
this kind of leidsjiar comes in direct contact with e([ually allotriomor-
phic (quartz, the boundary is an irregular one, and tlie two must be
supposed to be sviK^hrc^ious productions in the act of crystallization
of the i-ock. To wl^at class of feldspar it may belong is very difficult
to decide. It looks like adularia and fresh, while the enclosed
plagioclase exhibits more or less an advanced stage of decomposition.
Notwithstanding the fresh a])})earance of the feldspar, it displays only
weak j)olarization-colours, by which the other feldspars and quartz
are readily distinguished. Througli the want of crystal lographic
outliiies there is no means of getting any optical proof. Lately,

1 Zeitschr. f. Krystallographie. 1890, XVHI, p. 192

THE ARCH^AX FORMATIOX OF THE ABUKUMA PLATEAU. 93 ^

Dr. A. Saner and Dr. i^. V. Fssing, while stndying the minerals
of a pegmatite dyke, have fonnd ont, that tlie microcline occnrs
in simple crystals, or in twin- of tlie lîas^eno type, exactly like an
orthoclase-crystal ; and that characteristic, cross-liatching strnrtnre,
by which alone the microcline- nature is nsually recognized under
the microscope, is not always fully deyelopcd. 'l'he true nature (^f it
has been ])laced l:)y l)()th authors 1:)eyond all doubt by an exact
chemir'al analysis, and by optical inyestigations on the well-oriented
])rcparations. Tlierefore our feldspar, which is also not rloiibl\-
twinned, may perhaps be looked upon as a variety of microcline.

The granite Idtberto described tbrms a wild creek along the dee|)
rayine of the Xatsui-gawa, which runs at its L^wer course by the
]io])ulous town of Taira. Recently a new road was opened toward
^[iharu, and the traffic thereby very much facilitated ; but just a
few years ago, it was one'of the worst roads of tliis region ; hence tlie
name of the Jigoku-döri, or the Deyil's way. Xew road-cuttinu-s
now giye good exposures of the granite.

At various localities the hornblende-granite f)rms a gradual
transition to the so-called (jranite-fiiiris:^ ov <in('is.<;-fjmnili'. and we can
trace them step by ste]) from one extreme to the oflier, without find-
iiig any alnaipr discoutiiuiity. There are, howeyer, other (ineisses
occurring in the same region, whicli look, at first sight, like
schistose varieties of the preceding granite; but in truth the f uaner has
nothing in ct^mmon with the latter, in regard to its genesis. The
genuine gneisses, already referred to, are true members of the
arcbœan group, [lerhaps the lowest and therefore tlie oldest rocks which
we shall ever be able to find in tlie edifice of the fFaparjese
islands. Gord'usion of the genuine gneisses witli the apparent ones
bus thrown many of us into an intricate labyrinth, from which

282

B. KOTO.

hitherto none could find the way of enoape. The present writer
endenATjnrs to decipher, in snhseqnent p;\ii'es, the com]ilicnted mode
of arranii'eraent of these ancient complexes, and the stratigra])lnr';d
order of the schists of winch the archœan is C(^mposed.

The srhisto>ii' vnriety — the o-neissose g-ranite — ,occnrring in connec-
tion with the h()rid)lende-,iiTaiiite, and forming a p;u't of one and Hie
same mass, is only a dvnanio-metamor])hic facies, hnt bronght about
under special conditions. The stowings, foldings, and faultings of the
masses of rocks, so common (bu'ing a mountain-building, have occurred
in the Abukuma plateau only ar tlie marginal zones ; while the
portion, of which the central height is formed, has remained quite
intact. There has lieen ])roduced a differential movement, leaving
tVie interior as a staiubng l»lock, called geologically the Har.^l, tlie cast
niid west sides of the plateau being thrown down to a lower lc\el,
alono- the meridional dislocation-lines.

Pacific.

% ABUKUMA PLATEAU.

\ \

Llcal profile of the Aliukuiua plateau.

I liad frequent occasi(Mis tf. (»1 serve, during my short \isit,
occiuTenccs of the scliistose variety (gn) alc^ng the Pacific const, and
also along the Abukuma-gawa, while the height lying between them
is occupied by a normal, typically granular gi-anite. I shall come
again to the same subject, when speaking of the geotectonic condition.

G

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 533

It ]nay ii«)t be out oi ])lace to .speak sliortly aJ)out the n(jiiieiid;i-
tiire. It has now become ahiiost an imperative duty for petroJo^iists
io .separate .sli;ir])ly tlie grauitcH ïvoin the (jneissc.'i. Prof. Colien'
loii^' aii'O j)oitited out tliat 1)y gnei.s.s we luider.staiid a u'euuine struti-
form r(X'k ; and info «ueli a rock granite i.s ne\er transformed, however
[•erfectly tlie hitter niay .show the .scliisto.se structiu'e. Such rock is
properly (o be de.siu'nated sc^histose uTanite. As uTanites ;ind li'neis.ses
are ueolouical Ijodies ijeneticaNv (piite dilferent, so and)i_ii'uous
Jiames bke uTanite-gnei.ss und ^ü;jiei.ss-L»ranite, ,<j;'iven to the metamor-
phosed njcks, had better l)e totally ex])elled for ever from petrou'raphical
literature. I follow the good exami)le of Prof. Cohen, and call
hereafter such dynanio-metanioi'pliic products scJiistosi' oranite^. In
order to avoid confusion, this is lundamentally nece.ssarv for a country
like Japan, where these schistose rocks are so largely developed,
occurring side l)y side with genuine gneiss, as fa* example, in the
southerii part of tiie Mutsu chain, in the moiuitaius oï Abukuma,
Akaishi, Suzuka, ivasagi, and Katsura, as well as in the northern [)art
of the South-Kiûshfi range'-'. I now returji to I he granite, namely :

h) Imycrfcctli) Scliislosi^ Aiii/iJilhoh'-Granilc.

As iius been alreadv ])ointed out, the transition to this is very
gradual, and there arises consecjuently a numlK'r of intermediate foians,
wiiich do not allow of biicf (diariicteri/.atioii. As we approacli the
scJiistose grani I e t'v(n\i n vejr'ioii oi^ II oriiui h rock, it is hardly perceptible
wliere one begins and tlie other ends. On large exposures su(;h
transiti(jnal r(3ck8 may be best seen by their petailiar habitus, somewhat
deviating from a normal structure. On t!ie other hand, specimen«

1 Geognost. BescJir. d. Umfjegoid von Heidelberg, 1881; see also Ueber dax kryntallinische
Grundgebirge der Insel Boniholm.

2 T. Haracla, Die Japanisdien Inseln, Tokyo, 1890, p. 46.

234 ^ KOTö.

tnkeii from siicli ;i spot give scarcely a clue as fo their true nature,
especially hy examining them on a fractured surface, (îorresponrling to
the ]>Jane of scliistosity ; hut on a face hroken across that plane, the
hlack components sliow a taint indication of ai'rangement in a
definite plane. Fn small chips, even tliis structure can not 1)e dis-
cerned.

Under the microsco|)e with thin ])reparations, however, nianv
])roofs of its heing affected l)y a media nical deformation l)ecome
evident. First of all. the uninjure<l quart:-grains a Ireadv show a so-
called undulatory extinction ; dixerse net-works of the hands of liquid-
inclusions gTov7 numerous ; and adjoining faces of quartzes among
themselves get more and more irregular, dis])lavinü' vivid mosaic
colours under ])olarized light l)etween crossed Niçois, hut not so the
faces adjacent to other components. Tlie innate hut latent twinning
lameliation of felihpars hecomes visihle l)y tliis time througli the
mass-jnotion of mountaiiis. The feldspars polarize in hrilliant colours,
and show also undulatorv extinctions akin to the connate quartz. Biotite
in normal granite has usually a regular outline, hut iji this transi-
tional rock the original form is now more or less ohliierated, showing
wavy l)ands, and its characteristic nacreous lustre hetween crcjssed
Xicols. The l)iotite is loosened and fihrillated on the side in direct
contact with the feldspars, and the latter specially kaolinize at the
adjacent portion of the mica. C(^iise((uently, the cause of alteration hoth
of feldsp:irs and mica is )iot mcrelij iiimospheric, hut mast he ascrihal to .some
inner movement of the rock. It is particuhu'ly noticeahle to find frequentlv
the secondary epidote (Fig. 4, XXiri). ivi conjunction with degeneration
of hotli mineruls, and the suhstratum necess;u'v for the formation of
epidote may prcjhahly have heen contrihuted hy hiotite and feldspars, just
as in tlie case of other react ionari' mineraU. The usual alternation of the
üTcen, hleached hands v^ith the fresh lamellai of hiotite makes here its

THÉ ARCH^AX FORMATION OF THE ABUKÜMA PLATEAU. 235

appearance. Fine, microscopic, trichitic needles are abundant in
the qunrtz, Tlie iir.^t iitduccment to tlu schistositij of our granite is to
he found in a slifjlit shifting in the positim of tlie ferro-magncsian
silicates, and also in the com men cement nf granulation in the solid quartz.

In the rock forming- a cheek of the deposit of magnetite in the
Chiika valley, whicli may conveniently l)e classed among the [)resent
o-roup. I found many patches of the micropegmatite, filhng up the
interstitial spaces between the constituent minerals. Felds})ars are
beautifully zoned, and polysynthetically twinned ; their peripheral
]>ortion is astonishingly irreguhu', gradually fusing together with
the feldspar-substîince of the niicro]}egm:'.tite. The feldspar tbrniing
the marginal })orti(ni, above mentioned, has the appearance being-
formed l3y the secondary enlargement, repeatedly spoken of, of late, by
many American and English authors. It is a subject ot consider-
able interest to know v.hether the pegmatite in question is of primary or
secondary origin.

Prof. Jude? recently advocated the view that the formation
of pegmatites and grano]jhyres'' may take place after the consolidation
of rocks by the way of devitrification, concentration, and differentia-
tion of a substance similar to glass-base, if there be any in granites,
that is to say, that they are not original but sec(,3ndary products. I
found the true pegmatitic structure in some of our schistose granites
as, for example, in the specimen from Chûka, a rock changed in its
texture bv pressure. This fict seems to have some important bearing
on the view of Professor Judd. just stated. Ihit I have also found
the same in some normal granites, which have not been even slightly
affected by dynamic changes. Under these circumstances no decision can,

1 Q. J. G. S. Vol. LXV, 1889, p. 179.

2 Professor Lossen wishes to substitute the word pegmatopliijre for the granophyre or
Rosenbusch, loc. cit. p. 270.

236

B. KOTO.

he made as to the orujin of the pegmatitic stnieture being primary or
secondary.

c) Sehistose Amphihole-Granite.

This modification may be readily recognized as such even on a
cursory examination of hand-specimens, and no confounding with tlie
normal granite is likely to occur. It is of a coarse, granulo-lamellar
(faserig) structure, and generally of a rather darker shade than the
primary rock. The schistosity is imperfectly developed ; consequently
the cleaved surface is exceedingly rough, irregular, and notched. A
typical rock belonging to this class is well exposed along the steep
ascent of the Kawachi togé (Kawachi pass), between the town of
Tomioka and the village of Kawachi, and is also found near to the iron
deposit of Chûka, Naraha göri. This is really what Mr. Kochibe
calls the "7/ca^'/ gneiss." All microscopically visible components are
now crushed into deformed bodies ; the hitherto even-lamellar bi(jtite
is altered into flexuous and wrinkled lamelltB ; the hornblende is no
lono-er of a prismatic form ; the quartz and hornblande are rolled out
and o'rained, and com[)acted into one mass with a feldspar centre zoned
by the grains of quartz, well seen on a weathered surface on account (jf
the different degrees of pel lucidity of the two minerals.

Examining with the microscope, the structure becomes more
apparent. Originally fresh minerals have acquired a dirty aspect and
become variously fissured. In the first place the biotite is for the
most part bleached, and its chloritic bands are interposed between
lio-ht-brown lamellœ. 'No trace of its original outlines is ])reserved.
A chloritic, fibrous substance often creeps al(jng the adjoining faces
and fissures of the compact biotite, and the fibrous mass is connected by
strino's from the mother-mineral, either hornblende or biotite. The horn-
blende has met the same fate ; its margins are irregular and frayed,

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 9,37

surrounded by accumulations of tlie epidote grains ; the peripheral
portions are chloritized, leaving cores of the hornblende in the centre.
The secondary epidote occurs fringed with chloritic fibres, and this
general distribution of the green minerals causes the rocks to appear
of a dark-green shade. The large well-defined crystals of mngnetite
are newly f<:)rmed ; the small crystals of it are heaped together in
the spot formerly occupied by the m agnesium-bi silicates out of which
they have been formed. The leucoxene mineral encircles the rounded
magnetite, from which it may be inferred that the iron ore is
titaniferous. The quartz is darkened and clouded with an immense
accumulation of liquid-inclusions, arranged in bands along the fissures
and cracks.

As to the feldspar it is for the greater part kaolinized, especially
in the central portion ; the periphery remains comparati\'ely in an
unaltered condition ; the original shell-structure and the chemical
difference in the zoning thus become ap|)arent ; the peripheral portions
of the crystals display weak polnrization-colours. Some feldspars
appear homogeneous by simple transmitted light ; but after applying
crossed Mcols, twinning structures are well exhibited by different
colours in alternate h".mella3 ; and, moreover, extremely fine lines are
developed just across the twins of tlie first tvpe. These second twins
do not extend over the whole breadth of the lamelloä, but are usually
only partial, being very abundant along the twinning plane of the
albitetype. The feldspar, apparently of an orthoclase nature, is, tliere-
fore, really microcline, having the characteristic cross-hatching struc-
ture. Where feldspars come in direct contact with the chloritized
biotite, a zone of accumulation of epidote grains occurs in the substance
of the feldspar, around the altered biotite, in such abundant quantity
as to make that portion appear quite dull. The feldspar itself appears
at first sight simple and homogeneous, but when viewed by polarized

238 ^- ^OTo.

light it shows imdulatory extiDCtioris. Moreover, the whole substance
is composed of fine grains wliich are only made visible by the difference
of the optical orientation of the several fragments*. Between the
epidote zone and the biotite the space is still occupied by a feldspar, but
besides this, needles of epidote shoot across from the granular zones
into the substance of chloritic fibres (Fig. 4, PL XXIII). The forma-
tion of the secoudary epidote is due evidently to the reaction of hiotite and
feldspar.

As to the state of aggregation of the individiip.l com] »orients,
I have to add only a few remnrks. I have already ypoken nhout the
structure of the imperfectly schistose granite, which is mainly due to a
slight shifting of the coloured components, and this fact may be readily
made out from the deformation of their crystal lographic outlines. In
the present case the schistose structure is more perfectly developed than
the one just referred to, and is distinctly fibrous-lamellar, resembling
somewhat the structure known as the " eye "-gneiss.

Under the microscope the hornblende and biotite are seen to be
not only flattened and compressed, but the entire crystals were material-
ly altered into chloritic filtres, leaving here and there only cores of
hornblende and scanty remains of lamella? of mica. Sometimes the
decomposition has gone so far that a few epidote grains alone indicate
the spot which both minerals once occupied, but nothing of their sul>-
stance can now l)e seen. More than this, the allotriomorphic quartz,
filling up the s])ace left vacant by other components, is for the most
part crushed, presenting a mosaic by polarized light. Simultaneous!}^
with this granulation, the quartz fragments have been shifted one over
the other, penetrating into wedge-shaped interstices wherever they
have been allowed to do so. The feldspar is the most obstinate of all
the components, standing solidly in its original position, while other
ingredients have partaken of the general decompositions and migra-

THE ARCHJEAX FORMATION OF THE ABUKUMA PLATEAU. 239

tions. This lieino' the case, the fehlspar lias become encircled by quartz.^
and this, as I have already stated, may distinctlv be seen in hand-
specimens even witli the unaided eye, altliono-li the sabsümce of the
feldspar has evidently snifered o-reat contortion, as may be inferred
from tlie bending- of the polysynthetic laniellge.

Tlie nnhvinned, simple feldspar, a product of the second g-enera-
tion of the s;une mineral, has a habitus akin to that of tlie o-ranitic
quartz, having filled up the spaces l)etween the lamellated plao-ioclase,
hornblende, and biotite, and consequently imbedding the aboxe-men-
tioned minerals. It is highly probable that the ophitic feldspar, if I
may be a. I lowed to use this ex]3ression by analogy with the (jphitic
augite in diabases, is monosymmetric ; for, no polvsynthetic twi li-
nings have heretofore been observed in it. Tliis feldspar is a far later
pr(^duct of crystallization of the granitic magma, but its formation
took place slightly earlier or almost cotem])oraneouslv with that (^f
quartz, a.hhough no micropegmatitic structure has been produced. The
boundary between the later feldspar and tiie quartz is the most ir-
regular possible, indicating that they have consolidated not far from
each other in the order of crystallization. The later feldspar has not
suffered granulation, the (|uartz, on the contrarv, has been reduced to a
mosaic mixture.

d) Schistose Vqndote-Granite.

In macrosco])ic a|)])earance it differs from the ])receding bv its
dark shade, owing to the general distributiiMi tlirough it of chloritic
matters, and also to the presence of green patches of epi<lote. Its
structure is granulo-lamellar, nearly approacliing that of tlie plane-

1 This peculiar structure seems by no means to be of rare occurrencp. Mr. T'eall, while
speaking of the granite from St. Davids, which has given rise to a good deal of discussion,
incidentally makes the following statements: The relation of the quartz to the feldspar in thi'^
rock is interestinçi. Sometimes the two minerals occur in irregular grains, at other times the feldspar
plays the rôle of matrix to the quartz,... British Petrography, p. 318.

240 B. KOTÖ.

schistose modification ; transverse sections of the rock have a banded
appearance tliroiig-h alternation of feldspar-quartz zones with those im-
pregnated with chloritic matters.

Under the microscope, the coloured com])onents — ^the hornblende
and biotite — are seen completely crushed and fashioned into flat
spindles, and these resohed into green fibres, but some have cores un-
changed. Sometimes the hornl)lende has disappeared entirely, being
replaced 1)y masses of epidote and magnetite. The Inotite is bent, and
frayed out at the margins. Heterogeneous aggregates, consisting of
grains of epidote and clumjis of magnetite, together with chloritic
matters, form sinuating zones, contracting and widening at shoi't dis-
tances. The feldspar, the most enduring mineral, has escaped the general
destruction and granulation, excepting its peripheral portion, nähere the
texture is loosened and crushed, producing the cataclastic structure, and
there the chloritic fibres have settled, lining the horders of the feldspar. In
spite of the soUdilg of quartz, tliis ivas the first that gielded to pressure,
and its crushing ahead g seen in tiie (h) imperfectlg schistose granite, is
still more evident in the (c) schistose granite.

Lastly, in the schistose epidote-granite the quartz is totidly reduced
to fine dust. Examined by transmitted light, the qu;u*tz appears like a
homogeneous, colourless base, encircling and flowing around a s(3me-
what porphyritic feldspar. Fine dust is distributed throughout the white
mass, and the mass of quartz looks rough, as if it were, the sliced face
OÏ a mineral, like olivine. With crossed Niçois the masses resolve
themselves into a truly mosaic aggregate, one grain lapping over the
other, and flowing along round the deformed edges of the feldspar
fragments. The usually vivid colours of polarization, are now faint-
blue, and the extinction of light sweeps over from one part to the
other

THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. 241

e) Biotite-Graiiite.

Thi8 is coarse and o-ranular and of a lighter shade, being made
up of a -flesh-red orthoclase, quartz, and a little biotite. Under the
niicroscope some muscovite may be seen, while this mineral is entirely
tvanting in the hornhlende-granite, alreadij described. The latli-shaped
feldspar with twinning lamellation extinguishes at small angles sym-
metrically Avith the twinning sutures, consequently this plagioclase
sliould be classed among the oligoclase series as in the other granites.
It is idiomorphic in comparison with the orthoclase, which usually
encloses it, and consequently the lamellated one must be the older.
The orthoclose is more or less kîiolinized, and its crystals are usually
twinned on the B;iveno type. The quartz has the same habitus as
that in the hornblende granites, and is ])Oor in liquid-inclusions.
The biotite is common ; zircon and the blot^d-red iron glance are found
as accessories. The rock occurs in good exposures at Kawa-uchi,
Naraha göri.

The most interesting fact in connection with this granite of the
Abukuma ])lateau is the occurrence of black ixitches of the hornblende-
granite caught up and enclosed by the light-cohmred hiotite-granite. The
enclosed granite is really the thigments with sharp angular edges,
torn otf with great fjrce from a mass of completely consolidated rock
of older date. The size of the fragments varies from 5 to 15 cm.
New^ road-cuttino'8 and the bottom of rivulets ex])Ose the structure in
full detail. Looked at fi-om a distance, the rock appears like a coai-se
conglomerate or breccia, or a mass stained with gn^ss marks upon a
white ground. It is indeed a, breccia of effusive origin and primary,
the older black granite, bearing the hornblende, being ceuiented with a
matrix of the younger 5ioi/i6-granite, tlie latter differing from the first
only in the different development of ferro- magnesian silicate. The
granite enclosing the older fragments is wide-spread in the region

242 ^- k:otö.

of the western brim of the Abukuma pLiteaii. CouiineiiciLig from
Miharu, and extending northwards, the outskirts of this region may
be found on the left side of the Abukuma-gawa near Nihon-niatsu.

Examining tliis rock more closely with high powers, many in-
teresting facts are unfolded by the microsco[)e. The boundîiry between
the two granites is sharp and abrupt ; the encl(jsed rock is ^'ioiently
broken at its margin and terminates ^vilh keen edges, forming here
and there coves and inlets Avithin the confused mass, where the intru-
ding or younger granite has puslied its material through any free space.

The intruding granite. — The younger granitic portitni is cpiartzose
at the junction, consequently it rarely happens that its components
other than quartz come in direct contact with those of the enclosed
rock (Fig. 1,^ PI. XXIII). The cpiartz is here variously fissured and
broken, and the lines of fracture thus pr(xluced run approximately
parallel with each other, tlieir prevaihng course being directed
ao-ainst the extended mari'-in of the enclosed rock. The quartzes at
the junction are dotted with swarms of liquid-inclusions which increase
in number as they appr(xtch the meeting points. It is usual among
contact phenomena to observe the develoi)ment of air and gas in-
clusions, which, contrary to our expectation, is not the case in the
present rock. The lëlds})ars rarely happen to meet directly with the
components of the enclosed granite. Where they do the feldspars
are not homogeneous, and intact ; the substance of the crystals is
crowded with [>atches of a colourless mineral, and consequently
the wliole aspect simulates the appearance of either andalusite or
staurolite with rich inter})Ositions of quartz. Some of these interposi-
tions of the feldspars may be of a negative character, made hollow
by some etching solvent along the plane of chemical weakness ;

1 The lower half represents the intruding, young (Ijiotite-) granite, the upper half
the intruded, older (hornblende-) granite.

THE AROHiF.AX FORMATION OF THE ABUKUMA PLATEAU. 243

others again are real ench^sures of either ([uartz or feldspar with other
optical orientation than the main mass, while the third are rather
laro'er patches of another kind of feldspar with systems of twinning-
striations nearly at right angles to those of the enclosing minerals.
The last have a, close similarity to that of the alhitized orthoclase of the
Socotra granite, as descril)ed and figured by Dr. Sauei-J from which,
however, thev diifer only in one particular that the changes which
the mineral has undergone are not in orthoclase. hut in the substance
of a striated feldspar. The orthoclase is romparatively free from these
])atches of ])lagioclase, but full of irregular cracks. The quartz out-
weighs the striated and the non-striated feldspars, therefore this rock
nuist ])e of highly acid composition. Minute ci-ystals of apatite <are
abundant in quartz near the margin of biotite, being often dismember-:
ed and crooked ; the j)leochroic halos are obser\ed in biotite ; globular
o'rains of maofnetite are scattered tln'ouii'li the oeneral mass. Zircon
is also found in fine crystals in the condji nation of the fices of j: T,
andx Px , with indistinct terminations.

The cnchm'à <iranittc patclics. — The ]>lagioclase is idiomorphic
with respect to that of the biotite-granite, and at the same time zonings
are beautifully developed in it, whidi are not found in that of normal
h(^rnblende-granite. At times its central portion is more or less
decom])Osed, and crystalloids of a bottle-green hornblende are scatter-
ed throughout that area (Fig. 7, V\. XXTH). The feldspar is on the
other hand fresh and intact in its outer, and the hornblendes within
the core were probably formed by contact metamorphism. Epidote-
grains of a tolerably large size occur enclosed in an ajiparently un-
changed feldspar. The epidote seems to be wanting in the biotite-
granite (intruding granite). Striated and non-striated feldspars oc-
cur in equal quantities, but their distribution in the rock-mass is not

X Zeitschr. d. deutschen, geol. Gesellschaft, Vol. XL, p. 14G.

244 B. KOTÖ.

uniform. As a general rule they are in fine crystals. The .same
glohular interpositions, already spoken of, make their appearance in
these feldspars as in those of the intruding rock, and the (piartz ])ene-
trates into the suhstance of the feldspars, just like the pockets in the
quartz of (piartz-})orphyries. The liornblende forms the most im-
portant of all the components not only in respect of its quantity, but
of its very occurrence in the rock ; while in the enclosing granite we
fail to find even a trace of this mineral.

Tliis f ict affords us a clue to the two granites being of totally
diflferent origin, and by no means mere bands, such as might arise
from local differentiation and partial movement of a granitic magma.
Moreover, the ano'ular and broken outlines of fras^ments of the rock
speak for the foreign origin of the hornblende-granite ; and the pre-
sence of the amphibole in this and the absence in the other give con-
clusive evidence as to the really fragmentary nature of the older granite
caught up by the younger one.

The hornblende is dark bottle-green, and non-pleochroic, or, if
at all, very weakly so. It is destitute of its own form, its apparently
regular outline being due to the mutual dispositions of the neighbour-
ing quartzes and feldspars. The mica is comparatively idiomorphic
with respect to its closely associated hornblende, and grows round the
hornblende in clusters. The biotite is often enclosed in the hornblende,
consequently some of it must l)e younger than the mica. It is high-
ly probable that the imperfect ness of the shape of the hornblende is due
to its simultaneous formation with the feldspars. The quartz is com-
paratively rare, and contains abundant li(|uid-inclusions. Titanite in
the form of o;rains is also found which is wantino- in tlie biotite-ofra-
nite. Ijlack iron-glance, reflecting somewhat bluish rays, is plentiful ;
some yellow pyrites is present. These iron ores have hitherto not
been discerned in the biotite -granite itself.

THE ARCHiEAX FORMATION OF THE ABUKUMA PLATEAU. 245

YI. Petrography of the Takanuki Series.
A. Gneiss-Mica-Schists.

This occurs in a tiilnüar form with the plane-parallel structure ; the
surface of a cleaved slab of this rock is entirely covered with aggregates
of biotite, while its transverse section is striped with black on a
yellowish- white ground. This peculiar appearance arises from the
interbanded zones of black mica in the quartz-feldspar layers ; the
general colour is light-grey with a slight tinge of yellow, being caused
by the pigment of the hydrous sesquioxide of iron that has infiltrated
every fissure in the quartz and feldspar. Where biotite forms a com-
ponent only in small quantities, this rock approaches both in ap]>ear-
ance and composition to a granulite. Of course, such a granulite
deviates in habitus from the typical one of the Mittelgebirge of Saxony,
in having a rather coarse-granular texture, and als(3 by the absence of the
so-called microperthite. Weathered exposures of this rock look not
unlike a disintegrating sandstone-mass.

The prevalent component is quartz, and the rock may fitly be termed
a biotite-schist. The quartz abounds in liquid-inclusions with enclosed
bubbles which on warming soon disap[)ear fi'om sight, indicating the
presence of liquefied c<!rb(jnic acid. These liquid-inclusions form
chains, traversing different grains, irrespective of diverse crystal logra-
phic orientations, as is frequently mentioned in writings on crystalline
schists. This phenomenon Avould be best studied in a slice, cut
parallel to the plane of schistosity of a rock, brought from Shimo-Matsu-
kawa, near the village of Takanuki. Contrary to my expectations,
it was, however, not observed in a slice made at right angles to the
former section, a fact indicating that the rock had yielded to pressure,
in the direction parallel to the plane of schistosity, but not in that at
rig-ht angles to it. In individual grains, hquid-inclusions are,

246 ^ KOTÖ.

however, not wanting, und s^Aarnl!>; of them cross« the rock vertical
]y to its bedding.

The quartz contains, besides, as enclosures, almost colourless
dodecahedrons of garnet, needles of zircon, and deep, reddish-
brown flakes of biotite — all making the quartz, between crossed
niçois, a])] »ear like a s])ongy mass. There are also fine, dark or
brown needles, sometiiues disjointed, shc^oting in various directions,
similar to those of the quartz in tonalité, which are so frequently
described, but whose natiu-e is so little known. i'he quartz is. as
usual, intensely chromatic, wheu viewed between cro.^sed niçois ; but
not all ihe quartzes found in this rock beha\'e in like manner. The
one which has been already granulated, displays vivid chromatic
colours ; while those which are still under high tension sho^v only a
weak grev tinge, and at the same time undulatory extinctions whi'-h
gradually sweep over the section one after another as is rotated. The
crystaUization of the silic;i must be of a comparatively recent date, as
may be seen from a grea.t number of ])re-existing miricrals contain-
ed in the substance of the quartz.

Still later in its crystallization, or nearly cotem])oraneous with
that of quartz is the feldspar which, as I have already stated, makes
onlv a small fraction of the whole rock which not infrequently passes
locallv into a tvpical mica-schist. There are, however, other cases
in which Ihe rock makes transition in another direction, 1)y taking up
a large quantitv of both monoclinic aiid ti-iclinic feldspars in becom-
irjo- a tvi)ical ü'neiss. Generally s]>eakinü', the distribution of the
quartzose and feldspathic comj»onents in tlie rock are very fluctuating.
One portion may be built up only of Cjuartz, while the other will be
highly feldspathic, so that in a coarse variety found near Daibara in
Shimo-matsukawa, any one may name one portion of the rock a mica-
schist, while the other may be reasonably taken for a typical gneiss ;

THE AEOH^AX FORMATION OF THE ABUKUMA PLATEAU. 247

but l)oth modificntious ni'e re.-illy one und tlie .sinie rock, and .should
not be interpreted ;is alternnrions of two.

The sLibotance of the orthochxxe i.s for tlie greater part k-aolinized,
and lias a dirty as|>e'T ; there is therefore no difficulty in discriiniijat-
ing it from the quartz grains, wliidi ase otiiervvise not veiy easy to
distinguish, when both are found togeth(-r unchanged. Tlie feIdH|):u'
appears üomctr/r-pohjßonal in outlines, owing to the dispo.^ition of
the hi otite and quartz ; and ] latches of it, widely separated from each
other, behave optically ahke, showing that they are all one mineral,
just as in the case of jiegmatite. Its j)olariz;ition-colours are weak, and
zonings are frequently oliserxed.

There occurs also another feldxpur which (k^^iates in habitus
irom the preceding in having a granular form, jiolysynthetic twin-
ning lamellation, and comparatively high polarization-color.rs. This
plagioclase is idiomorjjhic in comparison with the above-mentioned
orthoclase, and appears less altered than it. The plagioclase as well as
orthoclase often contains round grains of quartz/ around which the
feldspars show more or less signs of decomposition. The angle of
extinction of the plagioclase is small, making nearly 2° only with
the sutures of twins, thus pointing out theaiidesine-oli<j-oclastic nature
of the present feldspar.

The hiottte occurs in irregular folia?, and is of a reddish-liî-owii
colour ; nitile disposed as in sagenitc is found in great abundance ; the
pleochroi<^ lialos seen around thick but short cr\'sta]s of zircon may be
frequently observed. l)esides large lamellœ of biotite there (jccur
minute scal<;s of the same mineral. They are round or sometimes
rudely six-sided, non-pleochroic lamellge <^f microscopic dimension.s
with dee})-reddish-brown coh^ur. A spindle-shaped, lamellated,
highly pleochroic crystal is only a side-\ iew of the same mica,. These

1 Kalkowsky, Die Giieiss/ormation des Eulengebirges. p. 30.

248

B. KOTO

microscopic bodies are mostly found imbedded in quartz. The pri-
mary muscovife, though subordinate in quantity to that of biotite,
still forms a constant component. It is usually resolved into loose
folige, and occurs often interlaced with bleached, green, fibrous biotite.

Accessory minerals are zircon, and a cherry-red garnet, Avhioh
never occurs with crystallographic outlines, but usually in rather large
o-rains, lapped and encircled by the lamellae of biotite. It contains in
it manv l3rown scales of magnesia mica, gas-pores in the form of
dodecadedra, and also colourless grains which are usually supposed to
be of a quartzose nature. The garnet was observed microscopically in
nearly all the slides examined; it may, therefore, be looked upon as
a characteristic accessory C(:)mponent, and this fact makes some of
the rocks of this group appi'oach more closely to a genuine granulite.

Among the various modifications, the following are the principal
types : — gneiss-mica sclust, two-mica schist, garnet -hiotite schist, and
hornblende-hiotite schist.

A a) Gneiss- Mica- Schist.

Scaly, light-grey, thick tabular schist with the plane- parallel
structure, being made up of quartz, orthoclase, plagioclase, and biotite.
The last mineral is arranged approximately in one plane, alternating
with the quartz-feldsp:jr aggregates. The four components are all
nearly of the same size (1 mm.), and the weathered rock appears not
unlike a micaceous sandstone. The quartz and feldspars are present
in equal quantities, the former is often partially or wholly enclosed hy
orthoclase. The liquid-inclusions with the condensed carbonic acid
and bubbles are abundant in the quartz, being disposed in chains ;
other enclosures are round, tombac-brown biotite, clumps of the
opaque iron-glance, and only a few grains and prisms of zircon.

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. £49

The feldspars are of tAvo kinds, the «jiie ortlioclastic, the other
plagioclastic ; the Jatter is minute in size, poJysynthetically twinn-
ed with the angle of extinction of 8*'-4° with the sutures of the fine
lamellae. The orthoclase exhibits dull-yellowish polai'ization-colours,
and encloses often the twinned feldspar. Boihfeldspars are reiiiarJca-
hhi on account of tlicir enclosures of iiianij cßiartz -grains with diferent
optical orientations.

The micas are also of two kinds ; the tomhac-ljrown biotite in
ragged lamellae without ;iny crystallographic outline, with unusually
dark ])leochr()ic halos, including rutile-needles in the sagenitic form ;
the muscovite only in slight quantity, enclosing and often enclosed
by the biotite. Accessories iwe zircon, apatite, :ind iron-glance.

The rock ihmi Mshiyama, 1^ ri s<3uth from Takanuki, contains
many stiff, disjointed needles of sillimanite (Fig. 9, PI. XX III) ; the
one from the Nakayama pass, on the Nakayaina road, from Tanagura
to the province of Hitachi, contains a greeii. [il)rous biotite together
with white mica-. This rook is specialkj interesting in the possession of
impressions like etclied fgures on the surface of the cnjstals of its feldspars^
whicli are disposed one after another In series, parallel t<> the princpial axis
of the crystal. Moreover, large crystals of ide;dly pure andalusite (3
mm.) are present irregular in outline, and encircled by confused ao--
gregates of fibres of muscovite. A few of the crystals are coloured,
and then are pleochroic, and rose-red when the ])rincipal nxis of the
crystal is par:dlel with the short diagonal of the polarizer. I'here are
some traces of prismatic cleavage, which are made more distinct by
the infiltration of the hydrous sesquioxide of iron.

A h) Two- Mica- Schist.

A typical specimen of this variety may be found in the cliff near
Sôri, not fu' from Ishikawa. On a cursory glance it appears just like

250

B. KOTO.

a qiiartzite, being- essentially made up of quartz grain?* together with
thin layers of a brown biotite and silky mica. Under the microscope
the schist is seen to be don il t np of quartz, biotite, feldspars in small
quantity, and lastly, long, thin, lamellar, colourless crystals resolving
at both ends into stiif fibres. The last-mentioned mineral is travers-
ed by fissures at various points, arid is not beut and lamellated like
ordinary micas, showing thus its brittle nature. In the rock-mass
this com])onent is approximately arranged in a parallel direction ;
between crossed niçois it extinguishes light parallel to the bmger
side; its polarization-colour is vivid, coming near to that of musc(nite,
but it may be easily discriminated by the want of nacreous lustre, and
by a peculiar wavy structure when vie^ved between crossed niçois. I
conjecture this mineral to be margarite. Siauroscopic examinations
show on a cleaved face a wide optic angle, so much so that the cen-
tres of concentric rings scarcely lie within the microscopic field. The
dispersion of the optic axis for the red is smaller than that for the
violet ; i. e., /"C^, wiiile that of muscovite would be just the reverse.
The biotite is oftheu.sual brown colour, and is interlaced with the
lamellse of margarite ; it is found in far less quantities than the other
mica. The quartz fills up the interstices of the other components,
and is consequently wedge-shaped ; it shows intense polarization-
colours. Occasionally grains of feldspars may be noticed.

A c) (Tarnet-Biotiie-Sdnst.

There is no rock whicli varies so greatly in its (jutward appear-
ance as the garnet- biotite-schist. This is in the main due to the
varvinii" quantity of biotite. The one extreme is a highly quartzose
schist of a greyish colour, with its characteristic vitreous lustre, and its
weathered portion usually coloured brown. Micaceous zones are
indicated by dark stripes on the transversely fractured surface of the

THE ARCHiEAN FORMATION OF THE ABUKUMA PLATEAU. 251

rock. Tlie other extreme is a rather dark, imperfectly schistose, band-
ed rock with red crystals of garnet sprinkled all through it. The
microscopical components are the same in both varieties. The main
mass is made up of quartz-grains with the tombac-brown biotite
between them. The biotite is found in the substance of the quartz as
enclosures, but the grains of quartz are comparatively free from
liquid and gas inclusions. Muscovite is here wanting.

Accessories are sillimanite in fine radiating tufts (Fig. 3, PI.
XXVI), prisms of zircon, and clumps of iron glance. Garnet
is a never-failing but accidental component. In the iirst. the quart-
zose, variety of the schist the garnet «jccurs in minute, almost colour-
less dodecahedra, while in the second, the Ijasic, schist it is somewhat
large, granular, and cherry-red. The colour of the garnet seems to Jiave
some connection with the quantity of biotite present in the rock ; for, in
the dark varietv with abundance of the black mica, tlie "•arnet is red.
This mineral is, extremely rich in enclosures of quartz, and in nega-
tive crystals filled with air, so as to make it appear like some crystals
of staurolite.

A d) Hornblende- Biotite- Schist.

This is "exactly the same in its external appearance as the gneiss-
mica-schist, already described, differing, however, from it by the
presence of hornblende as an essential component, Tlie rock is grey,
and splits easily into an even tabular plate. The feldspars, both the
monoclinic and triclinic, make iqj the greater part of the mass, while
the amount of quartz decreases as they increase. The deep-brown
biotite and the bottle-green hornblende are intimately plaited toge-
ther, showing none of their crystallographic outlines. The zircon
and apatite, both in the form of grains, are especially aijundant in this
rock. Locality : Xishida, east of Tanagura, wliere the rock forms a

252

B. KOTO.

member of the complex of amphibolites and mica-schi«ts ; otlierwise
its distribution is not so wide-spread as that of the other rocks.

B. Titanite-Amphibole-Schists.

They form manifold alternations with the preceding rock.
They are the black, highly crystalline schists with the plane-parallel
structure, whose transverse section shows inter banded, thin, light-
colom-ed zones, recurring hundreds of times even in a small chip (Fig.
1, PI. XXVIl). If we move upward to a higher horizon, the rocks
become perfectly schistose, cleaving easily into a papery slab ; and as
their texture is not so compact as that of mica-schist, they easily fall
into a bluish-black, ashy powder on their weathered surface.

The («) black zone, when examined under the microscope, is seen
to be made up of a bottle-green hornbk'nde, whose pleochroism is
distinct, but not so pronounced as that of the brown variety, a,
yellowish-white, ß, oily-brown, c, greenish-brown ; the absorption
c>ß>a.

Isometric ijlagiodase-pulygans ^ are present, besides the hornblende,
in clear crystals free from any interpositions. All the polygons, so
formed from the disposition of neighboring grains, show undulatory
extinctions which sweep concentrically from one zone to the other in
the crystals, as the section is rotated. Only a few grains (1.3 mm.)
are coarselv twinned, with the angle of extinction of 7°-10°. or o°-4°

■J ' o

symmetrically with respect to the twinning suture, m that liere we
have probably before us an andesine feldspar.

The lamellge of biotite, with the interleaved bacillar horn-
blende, are oily-brown or green, but through weathering have become
so entirely decolorized as to be readily mistaken for a typical musco-

1 Vide ante, p. 2-16.

THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. 253

vite. Examined from the biise, the mica has a small optic angle,
and consequently should be considered as a variety of biotite. The
mica is present in fluctuating quantity, and it never takes an import-
ant part in the composition of the rock, but still it should be considered
as a characteristic ingredient of the aniphibole-schist, since it is entire-
ly wantino' in the series next above it. Thouo-h it occurs in meao-re
cjuantities, it may be readily recognized on the plane of schisto-
sity by its gold-yellow, glilter'nuj lustre. During field work we meet \^'ith
several amphibolites, all having nearly the same appearance, but belong-
ing to quite different horizons; the presence of the hiotite sliouhl, in tJwse
perplexing cases, be taken as a criterion for the identification^ of the
amphibolite of this series. We name this rock in the field the hiotite-
ainphihidite in order to discriminate it from other kindred varieties.

The iß) light-green bands in the schist, already referred to, difi'er in
many respects from the («) black zones rich in hornblende, by the
presence of a light-green augite. Here the grains of feldspar are of
minor dimensions, and for the greater part its substance has
been changed into an aggregate of a colourless, fine fibrous, confused
mass, which between crossed nic(3ls displays highly chromatic, aggre-
gate polarization-colours. The intact part of the feldspar appears,
therefore, here and there in a sporadic manner within the above-
mentioned micaceous mass, which seems to be identical with the
so-called pseudophite. This white band, sometimes attaining the
breath of 2 or 3 cm., is moreover very dirty, owing to an admixture
of titaniferous iron and highly refractive grains of titanite (1 mm.)
forming a rim of iron -ore, to which we shall have occasion to
return in the sequel.

The augite (Fig. 12, PI. XXI tl.) already referred to, occurs in
this band in great abundance, taking the place of the hornblendic
element, and even of the feldspathic component. It is found always in

254 ^ KOTö.

the form of isometric grains ; sometimes, liowever, elongated ones
(1 mm.) are observed, and along their longer axis rnn a few suture
lines which are traces of the characteristic cleavage of aiigite (Fig. 12,
d and e). The extinction of light takes place at a very high angle,
usually 30° or more, w^ith regard to the trace of the cle;ivage. It is
colourless or iliint-green. indicating the paucity of iron in it. The
colouring pigment, slight as it ie, is, however, not uniformly distribut-
ed, the peri})hery is rather of a lighter shade than the interior. The
mineral presents another very characteristic feature which is here
worthy of short consideration. There are many short, black streaks,
which run strictly parallel to the cleavage- direction, and are C(^ntined
exclusively to the interior of the crystal (Fig. 12, d and e). Examin-
ed with high powers these interpositions are found to he nothing but
negative, long, rectangular sj>aces, tilled witli air, or water with air-
bubbles, and the grains consequently look not unlike the diallagic
modificfition of augite.

Recently, Prof. Judd advanced a beautiful theory of the schil-
lerization — a phenomenon produced through tlie secondary infiltra-
tion of some substance into the spaces formed by certain solvents
along the so-called " solution-plane," or the plane of chemical weak-
ness, when the rocks containirig feldspar and also augite are sul^ject-
ed to high strains at great depth.' In the last number of the
Mini'ralotjical Magazine^, Judd has again submitted augites to the
same line of treatment which he had so earnestly advocated in his
former papers. The orthopinacoid of augites, he says, is the normal
solution-plane, and if once the twinning lamellation is induced to de-
velop in crystals, then along the planes of chemical weakness just the
same thing may be effected as in those of labradorite. I can not hut

1 Mineralogical Magazine, Vol. VII. (1886).

2 Ibid. Vol. IX. p. 192.

THE ARCHAEAN FORMATIOX OF THE ABUKUMA PLATEAU. 255

think the present augite rrpre.fipntfi in the non-aluminous group an incipient
stage of iiw formation of the so-called pseado-lujpersthene of an aluminous
augite.

Sometimes grains witli the aug-ite-cleavage are observed (Fig. 12,
a, &, and c), and these basal sections are marked witli numerous spots
which are nothing but the cross-cut of the cyhndrical lioles, well seen on
the longitudinal sections (d and c) of the mineral. There seems, how-
ever, no regularity in the arrangement of these dots. The pleochroism
is faintly observed only on the cliuopinacoid, when the interior portion
is of a darker shade than the peri])hery ; and the absorption is
the strongest when the principal axis coincides with the principal section
of the lower nicol. Some grains show intense polarization-colours
between crossed niçois, nearly equal to those of augite or olivine,
and these, when closely examined, always extinguish light in oblique
directions with reference to a few cleavage-traces. The grains with
straight extinction are on the contrary very dull, -ranging fr<^m grey
to light-brown.

The augite is scattered through the entire mass, to the ex-
tent of nearly the half, and when it occurs associated with a rather
green hornblende which is present only in small quantities, it is
imbedded within the sul^stance of the hornblende (Tig. 3, PI.
XXIIl), each having different optic orientations, as shown in the figure.

From the whole habitus I consider these light-green grains to be
the salite of Prof. Kalkowsky, wIkj was the first to point out the wide
distribution of this mineral in amphibole-schists. unfortunately his
original paper is not accessible to me, and a strict comparison of the
salite from the Oberpfälzer Waldgebirge with the Japanese mineral is at
present a matter of impossibility. Prof. Pecke' has also given a

1 Die Gneisaformatioii des nieckrösterreichischen Waldvierteh. Tschermak's mineralog. und
petrogr. Mitth. Bd. IV, p. 189.

256

B. KOTO.

short description of it, and its wide distribution in the amphibolites
from the Waldviertel of Lower Austria.

Apatite, which is so far not found in the hornblendic zone,
is present here in large quantities in the form of grains of nearly the
same size as that of the salite. It is not prismatic in habitus as
usually found in rocks, and in the present case, one might take it for
a light-coloured salite, but its faint-blue ])olarization-colours, its
characteristic dot-like enclosures, and its hexagonal cross-section
preclude its being confounded with the augitic mineral.

Lastly, the most interesting component found in the light-green
zone is the titanite (Figs. 5, and 6, PI. XXIII). It is not found
in well-finished crystals, iDut in those forms resembling rolls of
butter (weckenjörmig). Some are spindle-shaped, tapering at both
ends into sharp points. Others are approximately s|)henoidal, being
fissured transversely at various points across the crystals ; along these
fissures and also at fight angles to them lie the directions of maximum
extinction. We have here probably a basal view of the titanite.
The other very obtuse rliombs are its clinopinacoids with oblique
extinctions. There are still others which indicate no signs whatever
of crystallogra|)hic forms, but present shapes like falling drops from
the melted end of candle-wax.

In some of these clumps there exists a black, formless mass in
the centre, wliich I presume to be a titaniferous iron (Fig. 5). At
times the black cores nre of a tolerably large size, and the
titanite forms but a very thin coating around them. The titanite
is highly refractive, and has dark margins and a chagrined surface,
due to the total refraction of lio-ht that enters from the other sides.
Its substance is not very clear, and has some enclosures whose
nature could not be made out, owing to the high refraction of
the titanite. The polarization -colours are rather weak, ranging from

THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. 257

brown tf) grey ; but some drop-like grains are highly chromatic and
have a striking similarity with the olivine grains which are also said
to be found in some amphibole-bearing schists. Prof. Kalkowsky^
has mentioned the occurrence of olivine grains which ckister I'ound the
ir(3n-ores, iunl the figures of the olivine (glinkite) given htj him have a
I'emarlahle similaritg with the above-mentioned grains of titanite with the
enclosed titani ferons iron.' 1 have, tlierefore, some doubts as to the
real nature of the present titanite, and consequently have had it
subjected to a chemical examination which proves the presence of
titanium in it.

The titanite grains in the basic, hornblende zones mostly possess
black cores, and the minerals which accompany such titanite are
biotite and hornblende, b(jth being ferriferous components, while
in the acid, salite band the grains are usually /;Y'(;/rom the black iron-
ore. The first modification of titanite may be fairly compared with
the so-called titanomorphite, resulting from the decomposition of the
titanic iron ; Ijut in the present case I can not conceive the titanite-
margin to be derived from the black core ; they are original, and
should not be taken for titanomorphite.

The hornblende in the salite-band is pre-eminently green and
pleochroic ; the feldspar is one of the striped varieties. There is also

1 Die Gneis.fformation des Eulengehirges, p. 37-38. See also Dr. E. Dathes work:
Olivinfels, Amjjhiholit und Biotitfjneiss von Habendorf in Sclde^ien, in the Jahrbuch der königl.
preuss. geologischen Landesanstalt für 1888, p. 322-324. The amphibolites of the gneiss
formation of the Eulengebirge seem specially rich in the olivine grains, as may be judged from
Kalkowsky's and Dathe's work. So far as I know, I have as yet not come across the olivine in
any of the genuine amphiljolite-schists of Japan. The peridotites and serpentines, however,
often contain that mineral ; but they occur only in the form of intrusive bosses, sheets, and
dykes in the archsean memljers.

2 Mr. J. J. Harris Teall has given a s-iniilar figure in Plate XLVII, fig. 3, in his " British
Petrography " with a note that it " shall rei:)resent a kernel of iron ore zoned by sphene."
Unfortunately he was obliged to postpone all detailed references to this mineral to some fixture
occasion, notwithstanding the fact that the plate had been prepared of a glaucophane-schist
from Anglesea, in which the above-mentioned titanite is said to occur.

258 ^ ^^'^^•

a clear, uiistriped feldspar in the hornblende zone, which I also place in
the plagioclastic group.

The above notes chiefly refer to the rock brought from Kamada,
1 ri south-west from Takanuki. Having given a general description
of the amphibolites, we may now briefly consider their many modi-
fications.

B a) Titanite-Biotlte-Amphibolite.

This is the commonest type found all over the region included
within the terrain of the present series, so that the citation of its
occurrences would be quite redundant. It is thin-banded, and has a
plane-parallel structure. Sometimes, however, massive modifications
are not wanting; still their transversely fractured surface always shows
a banding of the white, feldspathose, and black, hornblendic zones.
The hornblende is brown and pleochroic, the titanite-wedges and the
lamellae of biotite are interposed between the bacillar amphiboles.
The clear, ])olygonal feldspar is of a rather large size.

The interbanding white zone is in the main made up of the last
mineral, and its grains are minute. Intermixed with these there are
chains of titanite-grains with the drop-like titaniferous iron. The best
exposures are found at IShimo- Yamagami near IVIatsukawa.

\) bj Titcmite-Salite-Ainphibolite.

This rock, so far I am acquainted with it, is only found at Ka-
mada, and its general description has been already sufiiciently given
in the preceding pages. It is a deep- black, somewhat granular,
thick-banded schist, alternating with the light-green liands (2-8 cm.)
of salite. The hornblendic zone is almost entirely made up of a bacil-
lar amphibole ; and through weathering a glittering, gold-yellow
biotite comes to view on the surface of the rock.

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 259

B c) Titanite-Feldspar-AmpJtibolite.

This approaches in its (mtward appearance to the first variety, but
it ma}^ lie reidily distingui.shed from the mica-bearing- amphibolites by
the absence of biotite. Also for the same reason the plane-parallel
structure, which is macroscopically observable in all hand-specimens
when the biotite is present, is not perfectly developed; the cross-section
is, hovve\'er, fine-banded, owing to repeated alternation of the Avhite
zones of feldspar with the black (jnes. The feldspar and hornblende are
nearly of the same size, and are fine when comj^ired with the two
preceding modifications.

The hornblende is grass-green and pleochroic, bacillar in form, and
is arranged approximately in parallel directions ; the feldspar is clear,
and polygonal in outline. The particles (^f the latter are minute and
granular in the wliite zones, and the titanite-grains, occurrino- with
them, with their usual black cores, are chained one ai'ter another, parallel
to the banding of the schist. Weathered rocks look not rnilike a
sandstone-mass. The sjjecimens examined are those from Sori near
Ishikawa. and Yamagami near Matsukawa. I sa\v some traces of
copper pyrites in them.

B dj Biotite- Amphibole-Gneiss.

This occurs in the titan ite-biotite-amphibolite as a lenticular mass
of scarcely half a metre in breadth, and can be easily distino-uished
from all others of the present series by a fine granular-lamellar structure.
A transversely fractured block shows in the cle:u-est manner the mode
of aggregaticjn of the comp.ments. The black, flame-shaped, patches
are nothing but granular accumulations of a greenish-brown, bacillar
hornblende with traces of the basal cleavage, and the white dots are
porphyritic, untwinned feldspars, nearly all completely changed into a

260

B. KOTO.

muscovite-aggregate but with some part intact on the periphery. The
rest of the rock-mass is built up of quite unchanged, colourless
feldspars with some grains of quartz, which on account of the jjarallel
position of the dark-br<3wn biotite assume a more or less wavy
structure. Only a few grains of the feldspars exhibit twinning
lamellation between crossed niçois ; consequently it is difficult to say
whether we have to do with plagioclastic or monoclinic varieties, but
probably the porphyritic feldspar belongs to the latter family. A
black, highly lustrous iron-glance may be observed, but not titanite.
The specimen here described comes from Söri ; but this gneiss might,
no doubt, be found in many other places by close examination in
the field.

YII. Petrography of the Gozaisho Series.

A. AmphihoUtes of the Gozaisho Boad.

We are in the hal)it of allowing so wide a latitude to amphibolite
or hornblende-schist, that the name alone gives scarcely any clue as
to the real nature of the rock a petrographer denotes by it, for the term
amphibolite which includes rocks differing greatly in their external
appearance and the nature of their component-minerals, as well as in
their genesis, that is, whether they are metamcjrphic schistose diorites
or really stratified schists. Therefore, it will be Avell here to give
certain prominent features which eminently characterize our rocks,
with the view of distinguishing them from the titanite-amphibolites
of the Takanuki series, already sufficiently described.

Besides the "Teat difference which exists between the horizon

o

of the rocks I am now describing, and that of the other series,
the following points are to be mentioned : 1) Perfectly fissile, evenly
plane-parallel structure is to a certain extent common to the rocks

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 261

of both series, but the upper part of the present rocks becomes
rather compact, slaty, or thick-taliular ; 2) colour more greenish or
greyish ; 3) absence of titanite and salite, compensated for by the
presence of chlorite, epidote, magnetite, tourmaline, and sometimes
rutile ; 4) structure not granular, but linear or parallel and more
or less compact, the last character especially giving solidity to the
rocks, so that they withstand atmospheric action better ; 5)
macroscopically, the mineralogical components are scarcely recogniz-
able in the green slaty rocks ; 6) microscopically, the ingredients,
especially the hornl/;iende, are in parallel and linear alignment,
so that a slide made parallel to the schistose plane presents the
same side of the minerals, whereas in the rocks of the Takanuki
series basal and longitudinal sections of the component-crystals
are visible in the same slide, lying confusedly together ; 7)
hornblende mostly needle-shaped or prismatic in habitus, while
in the other, it is polysomatic or tabular, or broad if prismatic ;
8) colour of the hornblende light-green, and not intensely-green or
brown.

The rocks comprehended under the present group vary greatly
as well in their external appearance as in their inward structure, to
such an extent that they do not allow of characterization in a few
words. They differ stratigraphically as well as petrographically in
mineralogical composition being accompanied by a change of structure.
From a highly crystalline, somewhat granular member bearing the
stamp of a genuine crystalline schist to a compact, green, slaty assem-
blage, they grade one into another imperceptibly without any marked
break. This may be traced advantageously in coming down eastward,
along the rapids of the Samegawa, from the plateau of Takanuki to the
boundary of tertiary hills, at the very junction of which stands the
small village of Kadôno (Profile C-D, PI. XXV.)

262 ^- ^oTö.

I begin with the lower nieml)er, a highly crystalline amphibolite.

a) It is a schistose, im) perfectly fissile, evenly plane-parallel, dark-
green, slatv rock, built up of multifarious alternations of white and black
bands, comprised of microscopically fine, glittering needles of a black
hornblende and saccharoidal, milky-white feldspar, disposed, as I have
stated, in fine zones. Sucli rocks diifer so little from those of the
Takanuki series in their external appearance as to lead one to
suppose them to be quite identical. However, on close examination
marks of distinction may be easily perceived. For besides the fineness
of texture which characterizes the present rock, the spangling gold-gellow
hiotite can not he seen on weathered surfaces of ü as on those of the titanite-
aniplnholite^ ; these surfaces are dark-green and dull.

Under the microscope the hornl^lende ;ip])ears compact, and
with irregular outlines, and als(j in ragged plates which are
either short and ol)long, or have tlie shape of slender prisms. The small
prisms are arranged more or less parallel. The broader plates are
less parallel, crossing e;ich other at various angles, and giving a
coarsely felted aspect to the section. In the plates very fine
striations run parnllel to the base. As all the crystals of the horn-
blende are not disposed in ])ârallel direction, so basal sections are
sometimes observed in tlie combination of prism ntid clinopinacoid.
The mineral is of a dirty-green colour, and pleocliroic, varying from
green to oily-yellow. The general mass is made up of feldspar (and
some quartz?) with crystalloids of hornblende. The feldspar is not uni-
form in size, and is polygonal in outline ; its polarization-colour is
weak, showing undulatory concentric extinctions ; its substance is clear
and fresh. Only a few flakes of hiotite are to be seen on the cleaved plane.
Microscopically the biotite may be considered as an accessory, occurring
associated with the hornblende aggregates as brown, fibrous lamellae,

1 See ante p. 251.

THE ARCHiEAX FORMATION OF THE ABUKUMA PLATEAU. 263

devoid of externiil outlines. Masses of iron glance, both deep red
and opaque incxlilications, adhere to the crystals of the hornblende, and
also form local accuniiilations in them. This rock crops out at tlie dis-
trict-boundary of Kikuta and Higashi-Shirakawa, on the (lozaisho road,
being cut sharply by hornblende-granite, where tlie latter assumes
a more or less schistose structure (GHG, Profile C-1), Plate XX^').

h) Not far from the last locality, and directly overlying the pre-
ceding, we find a schist which is surely a modification of the rock
just described. It is a greenish, fine banded, imperfectly, fissile, feld-
spathose schist. witVi sericitic membranes and the tufts of a brownish
tourmaline on its cleaved surface. Under the microscope a bluish-
green, pleochroic hornblende assuming long, sheaf-like forms, is seen
in more or less parallel alignment, but Locally tlie crystids are thrown
indiscriminately together so as to form a more or less intricate felt-
work. The interstices between them are occupied by the fresh, clear
feldspar which is sharply bounded, polngonal, and well adjusted with the
neighhouring pohigons. These polygons are peppered through with
grains of black iron ore which, by reflected light, presents a bluish-
black lustre and lamellar structure. It is, therefore, iron glance, but
not magnetite, with which it is often confounded. The heart- and
knee-shaped twins of rutile are scattered through the section ; it must he
expresslij remarked that this mineral has hitherto not been observed, in the
allied rocks of the Takanuki series. This rock occurs associated with the
tourmaline-bearing mica schist, to be described in the sequel.

c) Some of the rocks higher up in the series, associated with
schists such as that just described, are very similar in appearance to
common chlorite schist. Indeed they are compact, bluish-green,
rudely fissile, slaty rocks which, on cursory examination, might be
very often taken for chlorite schists. Examined under the microscope,
the predominating mineral, the hornblende, is seen to be present in

264

B. KOTO.

the form of an intricate felt-work of fine prismatic crystals, appearing
not unlike the needles of sillimanite. Only a little feldspar is found
as a o-runular, weakly polarizino; aggregate, in which actinolite is rare.
The general ninss is full of tea-brown, hexagonal tablets and grains
of opaque iron gin nee.

d) The next in ascending order, and forming the basement of the
temple of Gozaisho, is a schist which not only differs in its external
aspect but i\ho in its minerulogical composition from those of the
preceding rocks. The appearance itself suggests at once that the rock
has suffered a great physical change by dynamic metamorphism to
siich an extreme degree, that the zones of feldspar, now appearing dull
and saussuritic, have been so torn and convulsed as to assume a puckered
aspect. The rock is finely crystallo-granular, massive and slightly
fissile, and imperfectly banded with milky-white, feldspar zones.

The microscope reveals that the schist is composed of a bluish-green
hornblende, dirty, greenish-brown biotite, crystals and grains of
magnetite, all arranged in parallel lines, and lapped over by thin
flocculent chlorite. A transverse section of the rock admirably discloses
the UK^de of arrangement in full detail. A greyish-green biotite and
the dust of magnetite togethei- make up special bands, running through
the rock and fl(jwing around the aggregates and sometimes large,
well-defined crystals of magnetite. Above and below, the band is
bordered witli an accumulation of magnetite, whence the bluish -green,
sheaf-like hornblende shoots forth in different directions into the fine
aggregate of white, feldspar zones. Some feldspar occurs in the shape
of large, irregular grains forming veinules within the microcrystalline.
mosaic of the same mineral. The feldspars are limpid, but some show
traces of alteration, and are traversed by in;iny fissures and chains of
liquid-inclusions with air-bubbles, in a direction at right angles to the
plane of schistosity of the rock.

THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. 265

I confess that I am totally unable to distinguish quartz from
feldspar when their orains are thrown together in a mosaic aggregate ;
but judging from the massive, feldspar-hornblende rock, from which
presumably the present one seems to have been derived, I naturally
deny the presence of quartz. It is particularly misleading that the
huyer crvstals of feldspar, which must have been and still must be sub-
ject to peculiar strain l)y pressure in such a metam(jrj)hic rock, display
polarization-colours of so high order as to lead one readily to take them
for quartz ; but from time to time a few stripes of different (-olours may
be noticed, which point to the latent existence of twins in the feldspar.
In saying so, my notion is not strictly to preclude the presence of quartz,
as this is reasonably supposed t(3 l^e formed in the metasomatic changes,
which any rocks, especially of eruptive origin, may suffer during an
orogenetic movement of the mass. I simply mean that grains which
may beyond doubt be regarded as quartz have not been observed. The
bluish hornblende bears evident mark of having been produced in some
secondary wjiy in its sherif-like fjrm, frayed at both ends and tufted
together in acicular bundles. Minute grains oï epidote (3ccur mixed
with accumulation of magnetite.

e) The rock lying east of, and conse(|uently (jverlying, the meta-
morphic schist just described, is a massive, fine-granular, green rock
without an}' fissile stru^-ture in a hand-specimen, though a few rock-
cleavages might be found in natural exposures. It appears like a
rock altered under the influence of cont;ict action of some eruptives.
The surface is speckled with white dots, esp>ecially on weathered speci-
mens, indicating the presence of much feldspar.

The granular structure of the rock may be better understood
by examining a slide with the microscope, it is seen to be mainly
made up of hornblende in ragged, sheaf-like or fibrous masses, frayed
out at the ends into radiating tufts. The hornblende is disposed in

9ß6 B. KOTÖ.

such a confused manner that within the microscopic field all possible sec-
tions of it may be seen, and hence the granular structure of the rock.
The hornblende is green at its margins, but light- brown at its centre ;
thus giving rise to zonings of colour of which, the peripheral, deep
shade is surely due to a slight change in the substance of the amphibole.
When the axis of mean elasticity ß coincides with tlie short diagonal
of the lower nicol, the differences in shade are inost marked, while in
the position at right angles to the former, i.e.^ c, the whole crystal
becomes greenish in C(jl<jur, and the zonings tlnis disappear.

The interstices between the hornblende are occupied hy feldspar
crystals which appear quite homogeneous by simple light, while between
crossed niçois they are resolved into dot-like, minute grains imbued
with the feldspar substance, and the arms of the interference-cross sweep
round as the section is rotated, after the manner of a spherulitic
mass of chalcedony. It m;iy be fairly inferred from the optic;d deport-
ment of the rock that after its granulatioii and crushing, its temperature
was raised htj orogcnetic moceiiient so far as to partially melt the feldspar
into a more or less plastic mass, or else that a molecular rearrangement
took place in it at a comparativehj low temperature. The substance of the
feldspar is made dusty by accumulation of microscopic grains of
epidote and crystalloids of hornblende. Formless masses of an opaque
iron ore are plentiful, surrounded by a dull, white, granular ac-
cumulation, probably of leucoxene.

t ) Tlie <jne occurring to the east of the last-mentioned, and near
the last house, the westernmost of Odaira, bx-allv called Sara^'ai, is a
medium-granular, massive I'ock of a dark-bluish colour, showing no
sig'ns of tissilitv. This 1 considered in the field to be a tine structured
variety of a gabbro and under the microscope I find it differs in no
essential point from this. The habits of the hornblende, magnetite,
and interstitial feldspar are exactly the same. The needles of secondary

THE ARCHAEAN FORMATION OF THE ABUKUMA PLATEAU. 267

hornblende, detached from the larger crystals are, however, plentiful
in the apparently homogeneous feldspar.

g) Finally, we come to the uppermost of the rock-series, now under
consideration, which is found along the banks of the Sameo-awa, at
the village of Odaira lying close by Negishi, not far fi-om the Iwundary
of the tertiary terrain under which the rock gradually dips to be seen
no more in this region. This rock represents the extreme phase of
development of the thick series of Gozaisho, the corresponding other
extreme is, as has been already stated, the one found near the west end
of the Gozaisho Narrows, just at the district-boundary of Kikuta and
Higashi-Shirakawa, and which I have already proposed to call the
feldspatJwse hornblende -schist. The present rock appears at first sight as
if it were made up of silt, ashes, and the paste of volcanic mud, con-
solidated and pressed subsequently to its present form. It is a rather
greyish, rudely fissile, slaty rock, simulating very much the appearance
of the clasto-amphibok slate of the Mihabu series^ which forms the base-
ment of the palaeozoic group of Japan. The present rock is glossy in
appearance on a cleaved face, and the greyish shade seems to l)e caused
by the light colour and aciculur habitus of actinolite, as well as by
the presence of minute grains of epidote, which make up no small por-
tion of the bulk of the rock.

Under the microscope almost the entire rock is seen to be built
up of needles and fil^rous shred-like masses with a decided tendency
to parallel arrangement. Exceptional cases are not rare, as there
are often-times found confused aggregates of fibrous matter, concealed
by chloritic membranes, having an appearance very much like the
antigorite-variety of serpentines, especially when viewed between
crossed niçois. The actinolite is of a light-greenish colour and weakly

1 B. Koto ; " On the so-called Crystalline Schists of Chichibu," in which the minute struc-
ture of the amphibole slate has been considered in full detail. This Journal, Vol. II, p. 112.

268 S- ^^'i'ö.

pleochroic. The interstitial, half-granulated feldspar, probably albite,
is visible through the flocculent chlorite ; and the whole rock is pep-
pered through with almost colourless grains and slightly yellowish
crystalloids of epidote.

B. Mica- Schist.

The mica-schist, interbanding with the amphibolites, may at
once be discriminated from those of the complexes of mica-schists
and granulitic gneisses of the Takanuki series, by its coarse-lamellar
texture and glossy iron-black lustre. Common mica-schists are,
as a rule, highly quartzose, and the biotite that enters into their
composition is usually scaly ; this rock, however, is highly micace-
ous, being for the greater part made up of lamelJse, but not the
hexagonal scales, of biotite. The rocks classed here as mica-schist
exhibit within narrow limits a considerable diversity, as well in their
outward appearnnce as in their microscopic aspect. Therefore, they
may be conveniently divided into two varieties.

«) A coarse-lamehar, somewhat wavy structured variety is basic
and rich in feldspars ; the tombac-brown lamellae of mica lap one over
the other, forming a thick, continuous membrane, and constitute
undulating zones with the quartz-feldspar aggregate. A cleaved
surface is not even, but lumpy or nodular, due to the local swellings of
quartz in the schist, into spindle-shaped assemblages well seen on the
transverse fracture, and these give a gnarled or knotted appearance to
it. In its outward aspect this rock resembles the so-called " Garhen-
scliiefer,'" or the graphite-sericite- schist of the Sambagawan series of the
author,^ differing, however, from the last- mentioned in the presence of
true biotite instead of a green, fibrillated, sericitic mica. The feldspar
occurs in poly somatic forms; simple twins are often made visible by

1 On the so-called Crystalline Schists of Chichibu; This journal, vol. II, p. 97.

THE ARCHAEAN FORMATION OF THE ABUKUMA PLATEAU. 269

the behaviour of different polarization -colours in the two-halves, as
well as by unequal angles of extinction on the right and left.
Its polysynthetic lamellar structure is rarely to be observed, and
then only partially, being chiefly confined to the margins of crystals,
and coming to an end abruptly near their middle. Maximum-
extinction takes place usually at very small angles with the twin-
ning-sutures, a fact which compels me to place this feldspar in the
andesine series. The great majority of feldspars occur, however,
in simple crystals, and should therefore be considered as orthoclase.
Some of the orthoclastic feldspar have acquired an " eye "-like
habitus, being of somewhat larger size than the neighbouring grains,
and encircled by the foliœ of biotite. The feldspar-" eye " has been
transformed into scales like muscovite, and encloses a mass of iron-
glance disposed in such a manner as to assume a fluidal structure.
Opaque iron-ijlance (not magnetite) enters into the composition of
the schist in such large quantity as would allow one to speak of the
rock as being literally charged with iron ore, and is found especially
in those parts where the foliar of biotite have been brought together
into a thick heap. Taking into account the considerable amount of
feldspar present in the rock, I propose to call it the feldspar -
biotite-schist. The rocks examined were brought from Shimo-ichino-
kaya (Sono-aua), Iwa-mae göri ; and Kamesaku, Ij ri east of Ota
in Hitachi.

ß) Another modification, a true biotite-schist, is rather fine-
granular, black or greenish-black, and a perfectly fissile, evenly
plane-parallel schist, being made up of alternations of thin bands of
biotite and quartz. A typical specimen of this rock is found at
Gongendö (Kami-Yoshima), not far from the town of Taira.
Feldspars seem not to be present, and if present are rare. Tourmaline
is the most characteristic accessory component, and through its

270 B. KOTÖ.

presence, I think, I may discriminate this schist from allied micaceous
rocks. The tourmaline is of greijisli-hroum, or sometimes of greenisli-
hhie colour.

(1) Of these the greyish-brown kind occurs in the form of
prisms with imperfect terminations, which enclose a large quantity
of the dust of iron glance. The mica occurring associated with this
variety of tourmaline is a hroim biotite in irregular lamelJœ, frayed
out at the margin into a felt-work of fibrous mass ; while the general
matrix in which it is imbedded is a mosaic of round grains of quartz.
There are other patches of much larger, angular interlocked quartz
forming irregular, sinuous bands in which biotite is proportionally
rare, while in the micaceous portion both muscovite and the brown
biotite are plentiful. The quartz is ideally pure, and in this point
the rock differs from those of the lower horizon. Round-edçfed
crystals of apatite are sporadically present.

(2) The schist with a dirty hrowmsh-grcen biotite, of the same
habitus as the preceding, appears somewhat like a chlorite schist
and contains the prismatic, grecnish-hhie towimdinc which clusters
at some places into a confused aggregate, a peculiar habitus not
observed in the other mica-schist. Angular grains of feldspar are
found intermixed with quartz, which through weathering may
be readily distinguished from each other. The yellowish-brown
needles of rutile occur in the foliie of the biotite in divergent-radial
arrangement. Garnet, the commonest accessory, is, however, not
present in all the schists of this group. Lwi glance is always more
or less jn'esent, taking the place of magnetite in the other roclis, lying above
and below this one.

C. Garnet-Chloritoid-Quartz-Schist.
Intercalated between the chloritic amphibole-schists of the upper

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 271

Gozaisho complex, we find a quartzose rock of an uninviting, dirty-
greyish appearance with a characteristic vitreous histre on its
fractured surface. Looked at from the side it seen to be formed of
fine banded, sKghtly rosy, garnetiferous stratulie alternating with
other greyish ones. Under the microscope it is seen to be mainly
made up of quartz, garnet, and chloritoid, severally traversed by
veinules of quartz. The garnet dodecahedra are plentiful, the rosy
zone being especially so mottled by aggregates of this mineral
as to make the section appear dull. The colour of the garnet is
fiintly red ; small crystals of it are, however, colourless.

The chloritoid occurs in lamellar masses with irregular outlines
and also in rounded forms. The latter are of plum-green shade, non-
pleochroic, and indifierent to the action of polarized light ; sections
of the former exhibit a few cleavage lines from which the direction
of extinction deviates at an angle of about 15.° The pleochroism is
distinctly pronounced, the rays vibrating in the direction of the
principal axis are plum-green, those at right angles to it, olive-
yellow. The thick, brittle, lamellar mass of this mineral has a
tendency to aggregate at certain spots, and the crystals of garnet
are here particularly abundant. The characters of our chloritoid agree
well in essential p(3ints (Photogramme 1, PI. XXVI) with those of the
Austrian occurrence whose description has been given by v. Foullon^
This rock is found at Naka-Misaka, near a water-mill, Iwamae göri.
Another rock belonging to the same category was taken from near the
temple of Gozaisho.

D. AmiyJiihole-Picrite.
The olivine rocks seem to be of a wide distribution within the

1 Ueber die petrographische Beschaffenheit der krystallinischen Schiefer, etc. Jahrbuch d. geol.
Reichsanstalt, 1883, p. 220.

272' ^- ^^To.

confines of the Abukuraa plateau, as may be judged from a number of
specimens which have been brought home from different locahties by
my colleagues ; but their modes of occurrence are unfortunately ver}'-
little known to me. T. Kochibe^ was the first who acquainted us
with the occurrence in the A.bukuma district of a dunite which was then
considered as an archsean schistose member. S. Otsuku, however,
found it occurring in intrusive dykes within pyroxenites of the
palaeozoic age. " It is a compact or fine-granular, dark-green or
light-brown rock, essentially built up of olivine, cliromite and a little
hypersthene. A fi-esh dunite is only known from Ishigami and Aka-
saka-Higashino, near Ishikawa in Iwaki ; and Saimaru, Taga-göri,
in Hitachi/"

I myself collected some specimens from other localities' entirely
new to Dr. Harada. One was found as an intrusive boss through
a salite-amphibole-tourmaline schist, at Naka-Misaka, and another
at Yama-gami, near Takanuki, the latter forming a dyke through a
complex of gneiss-mica schist and titanite-amphibohte. The peridotite
seems to me from its modes of occurrence to be of a decidedly
irruptive origin, injected through various rock-groups of different
ages (Profile -1, PL XXIV). But whether there are any near relatives
of the peridotite, which might substantially be connected at their root
with the olivine rock, or whether it is pressed up alone as dykes
through several fissures, quite independent of magmas of other rocks,
I am as yet not able to assert definitely.

It has been known for a long time that basic rocks at their
points of contact with others are particularly rich in olivine. Ex-
tended researches made by Dr. E. Stecher^ have well shown, how the
proximity of the intruded rocks could exercise an influence upon the

1 T. Harada ; Die japanischen Inseln, p. 75.

2 Contacterscheinungen an schottischen Ol ivimli abäsen, T. M. M. IX, 1887, p. 146 et seq.

THE ARCHJGAX FORMATION OF THElABUKUMA PLATEAU. 273

intruding basic magma in the formation of olivine in the latter. In
several of the papers by Professors Judd and Bonney it is clearly
pointed out, how fluctuating are the relative quantities of the com-
ponent minerals of basic rocks. It is frequently observed that, by a
slight textural modification, dolerite (diabase) gradually passes into
gabbro, by the disappearance of feldspar, into picrolite, by the dis-
appearance of augite, into troctolite, and, by the disappearance of
olivine, into eucrite ; while by the excessive development of accessory
constituents like enstatite and picotite fresh varieties such as Iherzolite
may arise.

The prevalent rock, and at the same time the foundation stone of
the Abukuma, is of intermediate chemical composition, to, i. e. the
syenitic granite, which is specially liable to form transitions to tonalité,
diorite, monzonite, and eventually to gahhro ; and it seems to me highly
probable that the olivine rock in question represents the extreme basic
member of the syenitic magma, which has sent out various offshoots in
the form of apophyses from the main mass in the bosom of the earth.
Being influenced by cooling surfaces which must have been com-
paratively large and many in such narrow fissures, a selective crystal-
lization has been induced in the magma, whereby olivine has been
formed at the expense of the other minerals ; and thus we have
several dykes filled u]) with rocks of a peridotic composition.

The olivine rock which came under my notice in the field should
be grouped together with amphihole-picrite. It is always very massive
in appearance, rarely exhibiting banded structure. Its irregular,
rounded blocks are often covered with a thin coating of a deep-red
colour due to decomposition, beneath which, however, the rock is
surprisingly fresh and of a dark greyish-black. Under the microscope
it seems to consist of a sheaf-like, colourless hornblende (tremolite)
piercing through the granular aggregates of olivine. The latter is

274

B. KOTO.

encircled by fibres of chrysotile wbich separate individual grains
from each other ; and as several grains behave oi)tically in exactly
similar manner, they must have been formerly parts of a larger in-
dividual which by serpentinization has now become detached and
isolated grains. The olivine-core is filled with the dust of chromite, and
also with round or rectangular grains of the spinel group. The spinels
are isotropic, and highly refractive, and have theref(3i-e dark margins.
Some of the opaque aggregates which might easily be confounded
with chromite are surely octahedra of spinels. Examined with high
powers the minerals are found coloured either dark-brown or green ;
the former may be jjicotite, the latter iileonaste or hercynite.

The colourless tremolite is bacillar in form, some rods attaining 2
mm. in length ; their terminations are never perfect, being always
resolved into tufts of fibres which, in turn, eventually pass into a fila-
mentous aggregate of serpentine. The substance of the tremolite is not
compact, and seems to be extremely thin; it is also traversed through its
whole stretch l^y fine divisional lines parallel to the princi])al axis, in
consequence of which the mineral displays only aggregate polarization-
colours. That the tremolite is the primary component and not a
secondary one is proved by the fact that it penetrates the remnant of
the olivine, and also cuts sharply the edges of thedismemljered grains of
the same mineral.

Tlie final product of degeneration of both the tremolite and
olivine is the well-known serpentinous mass ; the one originated from
tremolite appears in the form of splinters of wood, which are thrown
too-ether in such a manner as to form an imperfect " bladed " structure
(Balkenstructny) of antujorite ; while that resulting from olivine is
the fibrous chrysotile wldch produces a characteristic mesh- work, with
au-oreu-ates of chromite along the original fissures of the olivine.

A rock fi'om Saimaru in the collection of the Geological Survey is

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 275

a pure, fresh dunite, entirely made up of olivine grains with only
a little serpentinous matter j that of Akasaka-Higashino belongs to
the same species with exactly identical minéralogie composition and
habitus, but differs from the former in the particular that it abounds
with interposed picotite.

VIII. Dyke-Rocks.

A. Pegmatoplujritic Dykes.

Along the water- worn banks of rivers and road-cuttings, there
are found innumerable flesh-red dykes, severally interpenetrating
both the younger and older granites, and even the complexes of
ïakanuki andtGozaisho, and it is very remarkable to observe that
wherever a granite occurs it is usually accompanied by this dyke rock.

No solid rock could withstand exposure to such powerful external
aofencies as the alternate frost of winter and heat of summer, which
are excessive in, and very characteristic of, the climate of some parts
of Japan as may be witnessed in the [costumes of the people in the
half-yearly exchange from a cold -temperate to a, tropic fashion. All
the rocks of the Abukuma plateau, especially the granites of coarse
texture, are, therefore, soon reduced to an incoherent mass after new
excavations even within the short interval of a few yejirs. This neces-
sitates incessant repair of roads, in order to keep them in tolerably good
condition. Among such crumbling debris, the red pegmatophyritic
dykes, in virtue of their solidity, escape the general disintegration,
and stand up in bold relief in various directions crossing rivers and
slopes of hills, and giving thereby a peculiar character to the scenery,
when seen from a distance.

Guided by prudence, the people of the district use only this dyke-
rock for macadamizing durable roads to which it affords a firm skeleton

276 B. KOTÖ.

and solidity. It would be superfluous to cite every occurrence of the
dykes, since they are met with all the way through and in any part of
this region, like Jacks at every street corner. A large series of ex-
posures of the dykes under their least equivocal and most characteristic
conditions of occurrence may be studied on the ascent from Nogami
(Tamano-yu cold bath) to Chikenjö, Naraha göri, for a distance of 8
km. This profile is very instructive, as there are found in it the often-
mentioned two types ol granite, one penetrating the other, and both
passing imperceptibly into gneissose modifications, to which the name
" Iwaki gneiss " has been already given. Through these granites,
the aplitic, pegmatophyritic^ dykes, the granophyre of Rosenbusch, make
their way usually at low angles, and strike with the main axis
(N 10 E) of the mountain.

These in turn are cut at very steep angles by a number of diorite-
porphjrite dykes ^ Since the filling up of the red dykes (Peg.), the
country-rocks have undergone considerable tectonic disturbances to
which is due the formation of parallel fissures (Fig. 2, PI. XXIV).
Different parts have then been shifted one after another, causing a
continuous band of the dykes to appear like a set of stairs, and some
of these clefts have been subsequently filled up with the igneous
magma, which we now find in the shape of the black diorite-por-
phyrite dykes, as may be clearly understood from Figs. 2 and 3, PI.
XXIV. From what has been said, there is not the slightest doubt
as to the younger age of the diorite-porphyrite, and its formation
may perhaps have been at the time, when the crust in this quarter
had suffered the last orogenetic movement, in which state it has re-

1 K. A. Lossen, Vergleichende Studien über die Gesteine des Spiemonts und des Bosenbergs bei
St. Weiideliind verwandte benachbarte Eruptivtypen'aus der Zeit des Rotld legenden, Jahrb. d. Königl.
preuss. geol. Landesanstalt für 1889, p. 270.

2 I wish to substitute the word diorite-porphyrite for lamprophyre in Figs. 2 and 3,
PI, XXIV.

THE ARCH^AX FORMATION OF THE ABUKUMA PLATEAU. 277

mained since without any marked terrestrial disturbance. The black
dykes are surely of post-archagan age.

Deferring details about the diorite-porphyrite to subsequent
pages, I shall first speak of the material of the pegmatophyritic chjkes.
It is flesh-red and compact, breaking into polygonal blocks with
sharp edges. Under the microscope it is very simple, as in its macro-
scopic aspect, but it shows a very instructive structure. The main
mass is made up of nothing but quartz and orthoclase, regularly
intergrown and showing a hieroglyphic or à la grec form. The
only other ingredient, that is visible under the microscope, is a
skeleton-like magnetite which is transformed at the margins into
brown sesquioxide to which is largely due the reddish tint of the
rock. The quartz and feldspar are in about equal quantities ; con-
sequently it is difficult t(3 decide which of them should be considered
as the main mass. The latter is for the greater part kaolinized and
dirty, while the fresh quartz is charged with swarms of liquid-
inclusions.

The pegmatophyritic dykes occur, as has been already stated, in
regular bands of uniform but moderate breadth, traceable for con-
siderable distances. Apophyses have so far not been observed.
Such being the condition in which the pegmatophyre occurs, I felt
considerable diffidence in deciding as to its origin, whether, that is,
it is a primary secretion after the manner of a miarolitic mass, or a
filling up of cefts by lateral secretion, or lastly, an injected magma
from the earth's interior, solidified in the present form. The last
supposition seems to be the most probable, as the rock traverses
indiiferently all the varieties of granite, and even those of amphibo-
lite.

The macroscopic development of the preceding is, to speak morphologically,
nothing bat pegmatite dykes, of which we have opportunities to meet ivith in

278 '^- ^^'^^•

fl.s large a mimher as the pegmatophyre clißes. Pegmatites are usually
considered as an accidental, mineral aggregate, deposited from solution,
by lateral secretion. If we view our pegmatite from this stand-point,
its formation must be ascribed to an origin entirely different from that
of the pegmatophyre dykes, in spite of close resemblance in their mode
of occurrence, structure, and mineralogical composition.

My trip to the Abukuma district had for its scope to establish, if
possible, the stratigraphical sequence of archoean rocks, the study of
which has been long neglected by us, and which no one had attempt-
ed to follow in detail. Keeping always in my mind this import-
ant question, I had no time to avail myself of opportunities to make
observations on dykes in general, and I am at present not able to say
anything definite about the relation of the pegmatite and pegmatophyre
diikes. At the time I simply considered them to be all of one and ihe
same origin, which in renlity cannot be the case!

Thetrue pegmatite may be best studied at Ishikawa-yama, 2 km.
north of Ishikawa, where Kochibe had found a crystal of beryl in the
newly exposed dyke on the road- side. Large orthoclase, twinned on
the ]>aveno type, and equally large and well-shaped, grey quartz, pegma-
tically intergrown with the former, together with biotite and muscovite,
form the materials of the coarse dykes. Beautiful dykes of graphic
granite with biotite may also be observed at Gomisawa, 12 km. east
of Ono-niimachi. Microcline seems to form an important part among
their components. These and many other dykes, of which there
are ample variety, require more extended researches than I had time
to institute.

B. Dyhes of Aiigite-dioritic Lamprophyres.

A dyke of about 2 m., cutting through hornblende-granite, is
found in Nishiyama (Ogura), on the way to Tanagura. It is a

THE AROH^AN FORMATION OF THE ABUKUMA PLATEAU. 279

compact, dark- greyish rock in which are porphyritically imbedded
crystals of hornblende and augite (3 mm.). No other components are
visible to the naked eye. Under the microscope it proves to be'pilo-
taxitic, consisting of lath-shaped plagvoclase, needles of hornblende, and
magnetite, with scanty remains of some colourless basis, which fill up
the interstices of the crystalline ingredients.

The phenocrysts are plagioclase, hornblende, augite, and a
zeolitic mineral ; the first is long rectangular or square, occurs
in simple crystals, or in simple twins, all extinguishing in oblique
directions at more than oO.° In spite of the simplicity of the crystals
and the scarcitv of twins, the feldspar may be looked upon as a basic
plagioclase. Zonings of the plagioclase are well developed, the
central part being often hollow, and partially filled up with a chloritic
aggregate ; the peripheral zone is fresli and glassy. The hornblende
is greenish-brown ; its forms are never perfect, but eaten away
by magmatic corrosive action, and the crystals are in consequence
encircled by an aggregate of opacité and needles of augite. These
marginal masses are prolonged into long " tails," just as horn-
blende is in some porphyrites. Its pleochroism is quite pronounced.
Twins of common type are discernible onlif in that shape wliich
has been formerly considered as anomalous twins whose plane of contact
IMS said to he the prism zc^ 2 (120)} The augite is rare, its
habitus is andesitic, consequently its basal section is approximately
hexagonal, being bounded by the predominating faces of pinacoids,
truncated at the four corners by prismatic feces, and its colour is
light-yellow and non-pleochroic. Biotite and olivine are not to be seen
in the specimens hitherto examined. This dyke-rock seems to
have aldose resemblance to the comptonitic modification of the dioritic
lamprophyre.

1 Becke: Tschermak's Mineralog. unci petrogr. Mitth. Bd. IV, p. 365.

280 B- KOTö.

Xear Hfirimichi, south-east of Fiikashima, Kochibe has found
many dykes of a dark-green, fine-granular diabase in granite, contain-
ing grains of olivine. ' This may probably belong to the same class
of rocks as the present one.

A similar dyke may be seen in a vertical cleft of about 2 m.
within a nodular hornblende-granite at the boundary of Nakagura
and Nakatani (L P in Profile F-F, PI. XXV).

C. Dijhcs of Dionte-Porphyntes.

There are many peculiar dyke-rocks whose mutual relation to
each other, and to the country rocks are but imperfectly known.
I can give here only a preliminary notice of them, deferring their
microscopic detail to another occasion. Their mineralogical com-
position and structural form seem to deviate so greatly from normal
chß'e rocks, that I feel comulerahle diffidence in placing them in any
of the known class of lamprophyres. The dyke materials show
great variations within narrow limits. From a compact, grey
hornstone-porphyry to a light-coloured, coarse crystalline diorite-
porphyrite, they vary through a number of intermediate forms. Some
of them appear dark and fine granular, others are aphanitic ; while
a third modification is medium-granular with black hornblende-
crystals porphyritically imbedded within the greyish general mass.
In short, thev seem to have nothino; in common to them, but in
reality they are otFsprings from a common stock under deceptive
appearances.

1) The compact variety possesses the aspect of a hornstone-porphyry,
with sporadic crystals of feldspar as a porphyritic component ;
the general mass is grey, and is splintery with a conchoidal

1 Harada, Die ^axxinischen Inseln, p. 76.

THE, ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 281

fracture. Under the microscope nearly the half of the whole bulk
is seen occupied by granophyric bundles which consist of fibrous
feldspar and quartz arranged in a divergent-radial manner around a
feldspar-crystal, so as to form a spherulite. Between crossed niçois the
spherulite is divided into imperfect sectors which sweep along one after
another as the section is rotated on the stage. A lew plates of horn-
blende and lamellae of muscovite are irregularly intermixed with the
granophyric mass, from which it may l)e inferred that the spherulitic
bundles came into existence after the crystallization of the bi-silicates.
The formation of these bundles is probably the effect of an unequal
cooling, or they may have lieen formed secondarily in a manner
somewhat similar to that of devitrification l^y molecular rearrangement
and differentiation of an unindividualized mass.^ The remainder of
the rock consists of a cryptocrystalline aggregate of quartz and feldspar,
muscovite and green hornblende; most of the colourless components
becoming visible only on applying crossed niçois. Copper pyrite is
present.

2) The dark and fine-granular dyke rock has a few feldspar- crystals
as a porphyritic element. îio other minerals are discernible by the
naked eye. Under the microscope the porphyritic feldspar is found
beautifully zoned with different optical orientations in the centre and
the periphery, having an extinction-angle of more than !20° with the
twinning sutures; the decomposition begins in some from the core,
whereas in others just the reverse hapj)ens. The minerals of the
second generation are the bluish-green, fibrous hornblende, and
zonally structured, long-rectangular or square-shaped feldspar; while
the general mass is made up of needles of hornblende and lamellae of
tea-green biotite, lath-shaped feldspar, and grains of quartz. The
structure is holocrystalline-porphyritic. Accessories are apatite, octa-

1 Vide ante p. 235.

282 ß ^<^Tö.

hedra of magnetite, and a little epidote.

Through the preponderance of feldspar of the second generation,
the rock becomes dioritic in appearance with somewhat large crystals
of fibrous hornblende as porphyritic crystals often arranged in stellar
aggregates. Some of the fibrous amphibole contains cores of mujite,
from which it may be inferred that the hornblende of uralitic habitus
has been derived from the augite.

3) The thinl modification is black and fine-granular, and a dark
magnesian bisilicate glitters through it by reflected light. .Examined
with high powers, it is a panidiomorphic-crystalline aggregate ol lath-
shaped feldspar, and prismatic hornblende, together with biotite and
epidote. The feldspar is simple-twinned, rarely polysynthetic, and
more or less kaolinized and dirty, being full of muscovite, w^ith the
secondary epidote at the centre ; zonings are rarely developed. The
hornblende is prismatic in habitus with the clinopinacoid present, so far
as may be judged from the outlines of imperfect basal sections. It is
pleochroic; c = dark- brown with a slight tinge of violet, 6= brown,
a = light-yellow ; absorption, c = ß > ct. Forms of the hornblende are
never perfect, but ragged and tattered, as if it were, the resorption-
residue of larger individuals. This supposition is, moreover, strength-
ened l)y a beautiful emerald-green colouring of the peripheral portion
which is materiall)' connected with the brown core ; the former has
surely resulted from alteration ot the original amphibole. At first sight,
the hornblende appears like augite, for which it may be easily taken.
It seems to me that the present amphibole is likely to be one of the
sodium-bearing varieties, as otherwise the formation of the bluish-
green margins can not be explained.

A dirty green biotite is irregularly scattered through the whole
mass, and the dark colour of the rock is due mainly to the presence of
this component. Titaniferous iron is sparingly present with highly

THE ARCHJ3AX FORMATION OF THE ABUKUMA PLATEAU. 283

refracting margins of titanile. Zircon with well-finished forms is
also observed. The structure is more or less porphyritic. The part
in direct contact with the cheek of granite is typically porphyritic,
with feldspar, hornblende, and biotite as large components; while
the rest is a crypto-crystalline aggregate of grains of feldspar and
quartz, and also foliée <jf biotite, making the ground mass of a beautiful
fluid-like structure, seen in the bending of streams, and bands of mica
around the larger feldspar-crystals.

4) TJie coarse porplnjritic modification. — This ditfers entirely from
all the preceding rocks in its external appearance, so that any con-
founding of this with the other varieties is impossible. It is a
typically porphyritic rock with large, rectangular or broad-tabular
feldspa.r (3 nun.) imbedded within the greyish ground-mass. The
feldspar is zonal ly structured with differentiated optical orientations
in each zone. iSonie crystals are simple; a few are coarsely polysyn-
thetic with oljlique extinctions of abfjut 14° Avith the suture-line,
while about 23° with P/M on the brachypinacoid. Therefore, it
corresponds to the mixture of ab, an^, of the labradorite series.

Minerals of the second generation are also discernible by the
naked eye, if carefully examined. They are long-rectangular, polysyn-
tlietic plagioclase, devoid of zonal shells, and a greenish prismatic
hornblende with combination of the })yramid, prism, and brachy-
pinacoid. The hornblende is greenish-brown oc bluish-green, and
pleochroic. A dirty-green biotite is found with sagenitic rutiles in
apparently fresh lamella?.

The general ma^s in which the components of the earlier genera-
tions are found, consists of a crypto-crystalline aggregate of grains
of feldspar and quartz, and also shreds of a green biotite. Acces-
sories are rounded apatite, and titaniferous iron with the margins of
leucoxene.

284

B. KOÏO.

IX. Summary.

The Dfeneral results I have arrived at by mv atudv of tlie
archgean formation of the Aljukuma plateau may be summarized
as follows : —

This archeean plateau constitutes a portion of the ecto- peripheral
zone of the ISTorth Japan garland,^ jmd is separated from the ])aekbone
of the island by the longitudinal valleys of the Abukuma-gawa and
Kuji-gawa, while on the east it is bordered by the Pacific sea-board.
The south end of this arcluean zone has been the subject of one ' of
my former papers. The present one is the result of study made in
the northern prolongation of the same belt, i.e., the Abukuma plateau.

The archcTean rocks of this region are ]jrimarily separable into a
lower division, the Laurentian, and an u})per division which again
may be subdivided into two well-recognizable, leading groups, the
Gozaisho and the Takaniiki series.

The Lawoition is mainly composed of rocks of the grariitic,
syenitic, and dioritic types of mineral ogical composition, and panidio-
morphic-hypidi(jmorphic granular structure. These granitic-granular
rocks show in places different degrees of schistosity, depending u])on
the circumstances under which they have been formed. Accordingly
we have a number of foliated granites which may be conveniently
brouo-ht tofj-ether under the followinn: head;?, viz., 1) imiierfectly schis-
tose amphibole -granite, 2) schistose amphibole-granite, and, lastly, 3)
schistose epidote-granite. The young biotite-granite, though less ex-
tensively developed than the other, has also equi^•alent modifications.

1 The late Melchior Neiimayr, when speaking of volcanic islands, said: Vom Feuerland an
zieht nich eine Riesenkette gewaltiger Vulkane nach Norden, his Alaska, wo dann jene eigentümliche
Bildung geschtcun gener Vulkanreihen, meist auf Inseln gelegen, beginnt, welche (Festoninseln) man mit
herabhängenden Blnmengewinden verglichen hat. Erdgeschichte, I Band.

2 See p. 198.

THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU 285

These pathological varieties, so to speak, which go by the current
name of gneiss-granite or granite-gneiss, though very improperly,
are, no doubt, mainly dynamo-metamorphic products. Microscopic
analvses give at any time sufficient proofs of their having been atfected
in the wav indicated. My own detailed study of them shows that
the first inducement to the schistosity of granites is to be found in
the sliglit shifting in ]josition of the ferro-magnesian silicates, and
in the commencement of granulation in the solid ([uartz. In a
more advanced stage of schistosity as in :2), ordinary schistose
o-ranite. all essential comj^onents have been compressed into deformed
bixlies ; tlie once evenly lamellar biotite altered into flexuous and
wrinkled lamelhr with bird's-eye-maple shimmer ; the hornblende
no longer of a ])rismatic form ; and the cpiartz and hornblende
rolled out and grained and compacted into one mass with a feldspar
centre zoned by the grains of quartz, thus simulating the so-called
centric structure by migration of the graiuilar (piartzes. In the last
phase of transformation as in 3), the schistose epidote-granite, the
horn])lende has disappeared entirely, being replaced by a mass of epidote
and magnetite. The biotite is bent and frayed out at the margins.
Heterogeneous aggregates, consisting of epidote, magnetite, and
chloritic matters, form wandering zones. The feldspar, the most
enduring mineral, escapes the general disintegration and granulation,
excepting in its peripheral portion, where the crystal is crushed,
producing the cataclastic structure. In spite of the solidity of quartz,
this has always been the first to yield to pressure.

The cause of the schistosity is undoubtedly dynamo-metamorphic.
Extensive rendings and foldings hav<e taken place in the Abukuma
plateau only at the marginal zones, while the central height has
remained quite intact. V)y the orogenetic, diiferential movement thus
produced, the east and west side of the plateau have been thrown

-2^Q B. KOTO.

down to a lower level, along the meridional line of dislocation. Con-
sequently tlie ofrnnnlated and compressed varieties — the schistose
g-ranites — are confined to the above-mentioned tectonic lines, one alno«'
the Pacific sea-board, and the other along the Abnknma valley, as
may be cleai'ly understood from the diagram, ])age 232.

I have repeatedly spoken of the yonng and old gr-niites which
are by no means easily distinguishnlile from one another. They occur
in such a confused mnnner as to try the patience of even careful olv
servers; and many have entirely ignored the heterogeneous origin of
the two kinds of massive rocks. The best exposure, illustrative of
the mode of occurrence of the vouna:er biotite and rdder hornblende
granite may be found between IsliiknM^a-yama and Shimo-Kawabe,
where the two apjiear successively between the line of fiult after the
manner of ruin-marbles (Fig- 5, PI. XXIV), and moreover assume
at times a schistose structure. In this exprosure, it is clear that one
is the dyke-rock to the other, but the granites being developed in
almost e([u:d masses it is not easy to say which is the country-rock
and which the intruding one. Another very illustrative profile is
shown in Fig. I, PI. XX^^ in which such complicated modes of
occurrence of the granites are to be seen that their mutual relations can
not be easily determined.

Judging from the wide distribution of the hornblende-granite, it
seems to form the general foundation of the Abukuma plateau, upon
which are built up all the later formations. If this be the case, then
the hornblende -granite in the first section inust be the country-rock
through which the biotite-granite made its irruptions at several points,
the older one being itself already in Û\e solid state. In the second
section tlie same cannot be said ; for the two granites intermingle with
one another in such îi manner as to lead one almost to suppose that the
hornblende-bearing varietv must have been in a more or less plastic

THE AROH^AX FORMATTOX OF THE ABITKUMA PLATEAU. 937

oonditioîi ;it the snme time a.^ the other. It is thus a matter (^f
œnsiderabJe diffi'-iiltv to decide whicli is the eai-lier ^Tauite.

When speakiiii)- of tlie line of section at Sliimo-Kawahe (p. 271), it
lias been -dready shown that the brownish, .i>'ranulitic gneiss of the Lower
Tak^innki series. ;uT'om])anied by a niicp.eeons seliist with plenty (jf
g-arnet, has l)een so distiir1)ed in various ways and at numerous points
by the intrusion of biotite-granite, as to make one believe that tlie
gneiss-complex has been broken up and cemented subsequentlv
together by the matrix of that plutonic rock. Generally speakin^-,
tlie biotite-granite occurs only in the form of apophvses or of Ijosses
within other complexes. On the r)ther hand, the hornblendic variety
seems to be present in extensive masses, distiu-bing all the complexes
formed ])rior to the period of the Gozaisho series, in such a maniier
as if the whole I'akanuki rocks had been swimming on that m-igma.
The last-mentioned series, in all observed cases, is geologically separated
from the Gozaisho rocks by the interventi(3n of masses of hornblende-
gran ite.

The biotite-granite, as I have already said, intersects the Takanuki
series at numerous points, forming sporadic masses a,nd irregularly
ramifying dykes ; the relation of the hornblendic variety to the same
complex is, however, somewhat different. Near the contact tlie
Laurentian granite holds as enclosures sharply anguhu', sub-a.ngular,
or somewhat rounded blocks of mica-schists and amphibolites of the
Takanuki series. This is well seen (jn the Hanatate pass (A-lî, Pi.
XXY). The schistose modification of the same has likewise foreign
enclosures of the Takanuki rocks, as more or less attenuated bands
drawn out parallel to the foliation of the hornl)lende-granite and
confused with it (Fig. 5, PL XXl\).

These facts, taken in connection with the prevailing shattered
character of the Gozaisho, and of the Takanuki strata in particular, at

288

B. KOTO.

their contact with the Laurentian rocks, leave no room for doubt bnt
that these inchisions are detached portions of the overlying formations,
which, in a firm and brittle condition, have become immersed in the
nnderlying viscid magma, which subsequently crystallized out as
the Laurentian gneiss and granite. This mode of foliation of
the granites (plastic deformation) seems to have been produced by
differential pressures upon the tliickly viscid magma, inducing a
flow in the mass, similar to that endogenous growth of a volcano
by Naclischuh, experimentally observed by Reyer. To this fl(^w is
ascribable both the schist(3sity of certain foKated granites, and the
parallel arrangement of enclosures of foreign rocks imbedded in it, as
in the Rainy Lake region.^ It must be expressly remarked that there
is another process which leads to the formation of foliation, (juite
distinct from that just mentioned, wlvich may be termed that of
s:)liil di'funiiatio)!, since the schistosity is in this case brought about by
internal granulation of tlie component-minerals. Foliated granites,
which occupy extensive area in the plateau, owe tVieir structure to the
latter actioij.

The upper arcluean is represented by bedded formations, in which
can be recognized at least two leading groups.

One of them is the Takanuki series which is again divisible into
tlie lower acid, and the upper basic member. «) The former rests
directly upon the Laurentian. and its petrogra|)lrical elements are
gneiss-mica schist, two-mica schist, garnet-biotite schist, and horn-
blende-biotite schist, which together make up the considerable thick-
ness of 5,000 metres. All these rock- varieties have in common a
tabular form witli the plane-parallel structure, and their transverse
sections show^ the interbanding of black-mi (,'a zones with light-
greyish quartz-feldspar layers (photograph, figure 2, -Pi. XXVII).

1 Andrew 0. Lawson, On the Gealogy of the Rainy Lake Region, p. 131. et seq.

THE archj!:ax formation of the abukuma plateau. 2«^9

Where biotite occurs in odIv small quantities, they approach both in
appearance and compcjsition to a granuhte. Feldspars, both nionoclinic
and triclinic, usually make only a small fraction of the whole rock
which, in consequence not infrequent]}^ passes locally into a tv])ical
mica-schist. This complex seems to corresj'ond with Harada's Rioké
schiefer,'^ so named from the locality of Rioke, Süchi göri, in the
province of Tötömi, where the rocks were collected for the first time.
Harada seems to have given them that name simply with the pétrogra-
phie object of covering with it various schists of his gneiss system,
found near the village of Kioké, Vv"ith(3ut assigning to them any s])ecial
horizon in his stratigraphie scheme.

ß) The Upper Takanuki complex embraces multifirious alterna-
tions of 1) the titanite-amphibole schists a,n(l i^). the gneiss-mica
schists. The first are black, highly crystalline schists with the plane-
parallel structure, whose transverse section shows interbanded, thin,
light-coloured zones, reciu'ring hundreds of times even in a small cliip.
They are perfectly schistose, cleaving easily into papery slabs ; and as
tlieir texture is not so compact as that of the underlying mica schists,
they readil}^ fall into a bluish-black ashy ])ow(ler on their weatliered
surface. These Ijlack, fissile schists are peculiar! v characterized bv the
presence of titanite which is found in those forms which resemble rolls
of butter (wcclicttförm'uj), and wdth sometimes a black, formless mass in
their centre, which is pi'obably of a titaiji ferons iron. Another yery
interesting component is the salite which almost exclusively makes up
the stuff of the light-green zones. Jiiotite is [)resent, but it never takes
an iinportant part in the comp'osition of the rock; still it should l^e con-
sidered as a, characteristic ingredient, since it is entirely wanting in
the series text aljove it. It may Ije readily recognized on the plane of
schisiosity by its gold-yellow, glittering lustre. We name these

1 Loc. cit. p. 43.

290

B. KOTO.

titiinite-bearing rocks in the field the biotite-ainphibolites in order to
discriminate them from other kindred varieties. Tlie Ijiotite-amphibole
o-neiss occurs usualJy in lenticular masses. Those of the other cate-
o-ory (gneiss-mica schists) show the following moditications, namely,
o-neiss-mica schist, two -mica schist, "'arnet- hi otite schist, and also
hornblende-biotite schist. The whole complex, consisting of the
above-mentioned rocks, attains a considerable thickness, as seen in the
exposure between the hilly stretches from Nakagura to Söri (E-F, PI.
XXV), where this tapper Takanuki was found to have the thickness
of 5,500 metres.

The voluminous green mass of the (jrozaislio series is well exposed
alono' the banks of the Same-^awa whose river course runs nearly at
rio-ht anofles to the strike of the whole complex. Its basal member
lies in a somewhat elevated portion of the plateau on the west, while in
the eastern half of the section, towards the tertiary hills of Kadöno,
the younger series occurs, with a thickness which I venture to
estimate as probably not less than 10,000 metres.

The uppermost rock of this series is a greenish, rather massive
schist, cropping out along the l)aiiks in a vertical position but with a,
slight inclination towards the east. It has the aspect of a clastic rock,
and is like a hardened dej^jsit of volcanic aslies. This is followed to
the west by alternjite bands of green schists and quartz rocks, intruded
into at times by a hornblende-iJTanite. A i)lack mica-schist accom-
panies these green schists. They gradually disappe;u', to give place at
last to a black, crystalline, horriblende scliist which occupies the basal
portion. AVhen we compare the extreme members of these schists,
side by side, they seem at first sight to hax'e nothing in common with
each other, but on close examination in the field they are seen to
form a lithological continuity and a harmonious whole. These green,
fissile rocks have much the same appearance as the clasto-pyroxenites

THE ARCH^AX FOKMATIOX OF THE ABUKUMA PLATEAU. gQ]^

of my Mikabu series, whicli form the basement of the paJœozoic group
of Japan.

Sometimes they bear a striking resemblance to the chlorite schists
of my Sambao-;nvan series,' whicli lies directly below the ]\[ikabu com-
plex. The question ctjncerning the age of the Sambagawan series
involves serious difficulties. When the resu.lts (jf mv studies on the
schists of Chichibu^ were made public in 1888, I expressly remarked
that it is by no means safe to give the Sambngawan series a final
resting place in the archa?an group, without extended researches. In
spite of my warning -îgainst such a hasty conclusion, Dr. Harada"
assigned its place to the U])per archa3a,n, as had been done before him
by Dr. E. Xaumann. I do not as yet find any positive argument
that supports its archiean position, as no additional light has since
been thrown on the stratigraphical situation of the Sambagawnn
series. The relation of tlie Gozaisho series to tliat of the Samba-
gawan is unf^rtunatelv not very clear, and we must wait for some
time to come to see the final solution of the problem, whether
the two are geological e(|uivalents, or whether they succeed eacii other
in ])oint of time.

[ take here the opportunity of expressing iny tlianks to Professor
Edward Divers and Director Dairoku Kikuchi for tlieir kindness in
assisting me in various ways in the revision of. the proof sheets of this
paper.

1 This Journal, vol. II.

2 Loc. cit. p. 49.

B. KOTO, ARCHiEAX FORMATION OF THE ABUKUMA PLATEAU, 293

COTsTTEISrTS.

I. — Introduction

IL — The Abukuma Plateau

III. — Arch^an geology

iy._STRATIGRAPHICAL RELATIONS AND STRUCTURE— SECTIONS

Y. — Petrography of the Laurentian rocks

A. AmPHIBOLE-CtRANITES and BIOTITE-CtRANITE

B. Structural varieties of granites ...

a) A mphibole-granite

b) Imperfectly scJtistose ampJiiboIe-grauife

c) ScJiistose amphibole-granife

d) Schistose epklote-granite

e) Biofite-grcmite

f) Caught-up granite

VI. PfTROGRAPHY of the TaKANUKI SERIFS

A. Gneiss-mica-schists

Aa) Gneiss-mica-scliist

A b) Two- mica- schist

Ac) Gariiet-biotite-schist

Ad) Horvbleude-biotite-schist

B. Titanite-amphibole-schists

Ba) Titanite-biotite-amphibolite

Bb) Titanite-salite-amphiboJite

Be) Titan ite-feldspar-aviphibolite

Bd) Biotite-amphihoJe-gneiss

Yir. — Petrography of the Gozaisho series

A. Amphibolites of the Gozaisho road

B. Mica-schists

C. Garnet-chloritoid-quartz-schists

D. Amphibole-picrites

VIII. — Dyke-rocks

A. Pegmatophyritic dykes

B. Dykes of augite-dioritic lamprophyre

C. Dykes of diorite-porphyrites

IX. — Summary

Fagb.
197

198
200
201
218
219
229
229
233
230
239
241
241
245
245
248
249
250
251
252
258
258
259
259
260
260
268
270
271
275
275
278
280
283

PLATE XXII.

Plate XXII.

Topographical map, recently published by the Geological Survey of Japan, represent-
ing a portion of the extensive plateau of Abukuma between Tanagura and
Taira. It covers a portion of the province of Hitachi, and also that of Iwalïi.
The red lines indicate the positions of the line of section, given separately in
Plates XXIV and XXV, with corresponding letters.

h'til/î. 7Yir .ùr/u,r,l, /

Jouf. Se. Coll. Vol. y. FI. XXII.

.1/1. S/,imti (1,1,
.\'<, ,Vnlia I .l/MJ/r.l
Ka. Kiitiil /f'p/Jrr.l
.(/>. ,Ui,Êiuiii (.faul/i.)
Hi Hlf/nsfli (Ji\i.tl.l

jr,: Xi.iiii ( n-<:ti.j

A. JltliV (J/,:lHll./
M. Yit/tm ( lilttiiillti

PLATE XXIII.

Plate XXIII.

Fig. 1, — illustrates tlie point of contact of two granites, the lower lialf representing

. the intruding, young (biotite-) granite, the upper half, the iiitruded, older

(hornblende-) granite. Feldspar and quartz at their contact are variously

fissured, and the lines of fracture thus produced run a^'proximatcly parallel

with each other. (8ee p. 242.)

Fig. 2. — A bluish-green hornblende, forming an essential ingredieiit of granite.
(See p. 227.)

Fig. 8, — shows a green hornblende with the imbedded grains of salite, each having
different optical orientations. (See p. 255.)

Fig. 4. — Reactionary rim consisting of the grains and needles of epidote around a
decomposed biotite at the contact with feldspar. (See ps. 284 and 28Ö.)

Fi(is. 5 and 0,- — represent peculiar I'orms of titaidte, resembling rolls of butter, with
opaque, formless masses of titaniferous iron. (See p. 25().)

Fig. 7. — A somewhat large, allotriomorphic hornblende, enclosing a number of
equally allotriomorphic crystals of plagioclase, oriented in diverse direc-
tions. (See p. 227.)

Fig. 8. — Black dioritic patches of various sizes enclosed in hürnl)lende-granite, as
if a dioritic scum had floated on a granitic paste, and then been torn
asunder by some movement in a semi-liuid magma. These patches are
only a portion of the same granitic inagina, slightly different in chemical
composition. (See p. 217.)

Fig. *J, — shoAvs many stiff, disjointed needles of ? sillimanite. (See p. 220.)

Fig. 10. — Crystalloids and grains of hornblende, enclosed by a feldspar. (243.)

Fig. 11. — Section of the Nakagura valley, showing the heterogeneous nature of
schistose granite and the Upper Takanuki complex. (See p. 215.)

Fig. 12. — Salite, a characteristic component of titanite-amphibolites, with black
streaks regularly arranged parallel with the c-axis. (See p. 254.)

Koto, ArcJuean Formation.

Jour. Sc. Coll. Vol. V. PI. XXIII.

=p=v

y-P'

^x'^'iîS

Dark Dî^jri'tù' Grtuiite

Siri'à^ X.:,.-.h

10

N. Sasaki del.

Lith. <& Ivip. Seishibunsfui.

PLATE XXIV.

Plaie XXIV.

YiG. 1. — Section from Serigasawa to Miharn, tlie latter beiug the well-known town
in the Abnkuma plateau. It exhibits the complicated mode of arrange-
ment of granites. (See p. 219.)

gnBG, — schistose biotite-granite ; I gnG,— schistose hornblende-granite.

BG, — biotite-granite ; I

Fig. 2 and 3. — Cuttings along the newly opened road west of Tamano-yu, Naraha
göri, Iwaki, showing the relations of granites and dyke-rocks. (See
p. 276.)

HG, — hornblende-granite :
BG, — biotite-granite ;

Peg, — pegmatophyre-dykes ;
Lamprophyre, — diorite-porphyrite.

Fig. 4. — Section J-K, from Kami-Matsukawa in north-easterly direction to the
district-boundary of Ishikawa and Shirakawa, illustrating very clearly the
relations of the ïakanuki series, granites, and serpentine.

gnG,— schistose hornblende-granite ;
HG.^hornblende-granite ;
BG, — biotite-granite ;

UT,— Upper Takanuki ;
LT, — Lower Takanuki ;
S, — serpentine.

Fig. 5. — Section near Shimo-Kawabe, showing the relation of schistose hornblende-
granite and fleams of the Takanuki gneiss. The whole is traversed by a
pegmatitic dyke. (See p. 218.)

Fig. G. — ^Cutting between Tonda and Higashino, exhibiting black, attenuated patches
of the dioritic composition Avithin hornblende-granite, which arise from
chemical differentiation of its granitic magma. (See p. 216.)

Fig. 7. — Section near Ötsuka, as exposed on road side, bringing to view a gradua-
transition of hornblende-granite to its schistose variety within the amphil
bolite series of the Upper Takanuki. (_See p. 214.)

A, — gneiss-mica-schist ; I B, — titanite-auiphibolite ;

gnG, — schistose-granite ; I HG, — normal hornblende-granite.

Fig. 8. — Small belt of the Gozaisho rocks pinched in between granites. (See
p. 212.)

BG, — biotite-granite ;

b, — salite-hornblende-schist ;

d, — amphibole-picrite ;
gn, — schistose hornblende-granite.

a, — epidote-amphibole slate ;
c,- — chloritoid-quartz-schist ;
HG, — hornblende-granite ;

Koto, Archœan Formation.

Jour. Sc. Coll. Vol. V. PI. XX I \/.

N S

» 3 J/:; Km «

.^^Brnrnt^^^-^^^^^-^

/•/, ,irn ,,/<,, „i.s..^ A/ji,/ir ////A:

y^

^i(

■.':■ .nwKft,),^«'«^- -

Kr/'i'siiri' //flu^een Ton</a rinri //iflcis/imii,
Hiffa.shi-Shirnhatrii (,\7ri' .

f'Jji':po.vitre- at OùsuAsa/

ià I

ISW.

vm§jii/i§iim

K

> 9 Km

Lith. dt Imp, Seishibunaha.

PLATE XXV,

Plate XXV.

In this Plate, an attempt is made to illustrate by means of four sections the
general geological succession of the Laureutian, Takanuki, and Gozaisho divisions of
the Abukuma Archîean, together with the dykes of lampropliyre and pegmatophyre.
The positions of the line of section are indicated by thick lines, with corresponding
letters on the map, in Plate XXII.

Section A-B, from Hirakata on the Pacific sea-board through Nakayama to
Kawakami in the Kuji valley. (See p. 202 et seq.)

Section C-D, is drawn westwards from Kadöno, 12 km. west of the city of Taira,
across the ridge of Gozaisho, to the west of Takanuki. This is the best profile of the
whole region. MG=BG, /. e., biotite-granite. (See p. 204.)

Section G-H, from Ishikawa to Shimo-Kawabe on the right bank of the Abu-
kuma. (See p. 216.)

Section E-F, from the small hamlet of Kami-Misaka (where a patch of the
Gozaisho may be seen) to Ishikawa on the west. (See p. 212.)

Koto. ÄTchcecm Formation.

Jour. Sc. Coll. Vol, Y. PI. XXV.

'Pntain.fii ê'omi.-C

^'ntifil i: in., loa)

I Sc/ti.\-fi/.ve ////rrtft.-i

tj'i.raiafcc eoy,y,ylUx

rrillfcitrntn'li-

-^ G-^

/'fy///uUtr///u/rr-//i//rr

1 Trt/iHft/ 'tfitt /fa-v^ -

lAiK. é Imp. Seiihünntka.

PLATE XXVI.

Plate XXVI.

In this Collotype Plate, an attempt is made to represent the general features of

the most characteristic rock-sections, as they appear under the microscope. All give

the magnification of 140 diameters.

Fig. 1, — represents the rock-section of garnet-chloritoid-quarz-schist, one of the
members of the Gozaisho series. Colourless granules in the photograph is
the aggregate of garnet, while the irregularly outlined, black patches are
the plum-green lamellae of chloritoid. The white ground consists of
quartz. (See p. 270.)

Fig. 2, — -shows a portion of the light-green band in titanite-salite-amphibolite.
The crystalloids with a few cleavage-lines are the crystal-grains of salite,
while at the lower margin of the figure we find a basal section of the same
Avith its characteristic augite-cleavage. The white ground in the figure
represents the aggregates of feldspar which is changed into a colourless,
fine fibrous, confused mass, displaying highly chromatic, aggregate polari-
zation-colours. The intact part of the feldspar appears in a sporadic
manner within the micaceous mass which seems to be identical with
pseudophite or saussurite. (See p. 253.)

Fig. 3, — shows sillimanite in confused aggregate, occurring in garnet-biotite-schist
of the Takanuki series. (See p. 251.)

Fig. 4, — is the section of a typical titanite-biotite-amphibolite, in which are seen the
bacillar amphibole, and round titanite, resembling rolls of butter, some-
times with clumps of titaniferous iron in the centre. Locality : Karaada
near Takanuki. (See p. 252.)

KOTO, ARCH.EAN FORMATION.

Jour. Se. Coll. Vol. V. PI. XXVI.

_. . . ^, _^ mJi^§

Collotype by K. Ogawa.

PLATE XXVII.

Plate XXVII.

This Plate represents the appearances of the poHshed surfaces of the Takauiiki
and Laurentian rocks, at right angles to the plane of schistosity, excepthig Fig. 4.'
Fig. 1, — is the transvers esection of titanite-salite-amphibolite. The dark bands are

mainly composed of a bacillar amphibole, alternating with the white

bands of salite whose magnified section is represented in Fig. 2, PI.

XXVI. (See p. 258.)
Fig. 2, — shows the transverse section of a graniilitic gneiss-mica-schist of the

Takanuki series. Locality : Kamada near Takanuki. (See p. 248.)
Fig. 3, — shows also the transverse view of a schistose granite, from the Kawachi

pass, Naraha gori, Iwaki. (See p. 236.)
Fig. 4, — shows a view parallel to the schistose plane of a granite of a dioritic type

of mineralogical compo.sition, brought from Shimo-Matsukawa, on the

banks of the Same-gawa.

KOTO, ARCHAEAN FORMATION.

Jour. Sc. Coll. Vol. V. PL XXVII.

Collotype by K. Ogawa.

m m

m

m

n

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^

^

M

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t,

if

-t

i

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IH

m

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m

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^ Mi H

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T

^

On the Cause of the Great Earthquake in
Central Japan, 1891.

By

B. Koto, Ph.D., Rigakuhakushi,

Professor of Geology, Imperial University.

With Plates XXVIII- XXXV.

Introductory.

Contents. — Introductory. I. Dislocations. II. Geology and Topography of Mino and
Owari. III. The Great Earthqviake of the Mino-Owari Plain. IV. Various Views as to
the Origin and Cause of the Earthquake. V. Relation of the Great Fault to the Kecent
Earthquake. VI. The Course of the Line of the Great Fault that caused the Earthquake. VII.
Concluding Remarks.

Geologif^ts have rarely enjoyed ,so good nn opportunity as that
afforded them by the convulsion in the Mino-Owari plain, of observing
those great displacements of rocks called "y"«»/^.s," which may only be
brought about in the course of ages. Only a very few cases have ever
been recorded in the annals of earthquakes, of the formation of throws
of strata accompanied by subterranean shocks.

Lyell mentions in his classical work, Frinciple.s of Geology, a case
that occurred in New Zealand, in 1855. A tremendous earthquake
was experienced there, by which, especially in the vicinity of Welling-
ton, in North Island, a tract of land comprising 4,600 square miles is
supposed to have been })ermanently iq3i-aised from 1 to 9 feet. The
line of fault was distinctly observed in the sea-cliff, called Muka-Muka,
where the uplifted older rocks abut upon the lower. Tertiary plain
of Wairarapa; and the C(3urse of the fault was traceable inland
to the extniordinary distance of nl:)out 90 miles, in approximate! v

296

B. KOTO: CAUSE OF THE GREAT

nortli-soath direction along the Remutaka Mountains.

Another well defined case is that of the ever memorable Calabrian
earthquake of 1783. {The southern extremity of the mainland of
Lower Italy is chiefly composed of primeval rocks. Grneisses and
granites occupy the greater part of the country, being partially covered
by Miocene and l^liocene of the faciès of Fly sch. A great i^cripheral
or lomjiiiuUiial fissure is said by Suess,* to traverse the whole
length of that part of the country called Calabria, and along this
tectonic line, the fearful shocks of 1783 found their way, having for their
destructive centre the city of O])pido. The seismic activity continued
for some weeks, and the shocks spread north, south, and west, but
very little towards the east, chiefly confining their motion to the
fissured line of the fault. The maximum point of the convulsive
attack was transferred from one place to another through Soriano and
Polia up to Girifalco near the northern end of the fault, and then
returned with equal fury towards Radicena near Oppido, which was
the epicentrum. The statement of Dolomieu on this earthquake is
very interesting, especially from a geological point of view-. The
Apennines, he says, consist for the greater part of granite, and at
their base are seen new (J'ertiary) strata wliich constitute the plain
of Calabria. The usual effect of the earthquake, he continues, was
to disconnect all those masses of newer formations which were
supported only by lateral adherence. Hence it follows that throughout
the whole lenu'th of the chain Avide chasms were formed between the
solid granitic nucleus and the sandy Flysch soil.

The. lines of dislocation of Lower Italy and also that of Neir Zealand
are peripheral, i.e., longitudinal, running parallel u-itli the axes of the moun-
tains ; and in both cases it is remarkable to see either tl tat the dislocation has
taken place along the hoiuidarij of the two entirelij foreign formations ; or

* Das Antlitz der Erde.

EARTHQUAKE OP CENTRAL JAPAN, 1891. 297

else that the direct contact of rocks of different ages has been the residt of the
faulting or slipping of one upon the other. Geologists are altogether silent
as to wli ether the formation of faults and chasms should he considered as
the direct cause, or only tlie outcome, of sidderranean convidsions.

An unique, rhapsodic movement of land, and one which is often
cited in text-books on the authority of Sir Ch. Lyell, as evidence of
the actual upheaval of a lar<^-e tract of coimtry, is the formation of Illlah-
bund. The 'Mound of God' or Ullah-l)und suddenly made its appear-
ance at the time of a violent earthquake which occurred at Cutch, in
the delta of the Indus, on June 16, LS 19, when the fort of Sindree, on
the eastern arm of the river, sank down under the salt water of the
Runn. The Ullah-bund is not such a mound as is usually constructed
along a river, or thrown across a river-bed. It gives indeed the
deceptive appearance of an artificial dam, but only when we behold it
far away ; in reality it is the upraised edge of the land which imper-
ceptibly dips away inland. It has also been ascertained that this new-
raised country is upwards of fifty miles in length from east to west,
running parallel to tlie line of subsidence, while its breadth from north
to south is conjectured to be sixteen miles, its greatest ascertained height
above the original level of the delta being ten feet* Lyell saw in this
neivly created dam a trite upheaving of ground, while Suess considers it in
another light. According to him, we have here to deal not witli. the elevation
of land, or with the formation of foldings of strata near the siirface, hut with
the mere settling of the country in consequence of a pressing up of the ground-
tvater of a muddy alluvial plain. These eminent geologists seem, however, to
he in accord witli the view that the change in the relief in this special case
was the result, and not the cause of the terrible shocka which devastated the
Runn of Cutch, in 1819. The question at once arises in the mind,
" Was the tectonic disturbance the cause or eifect of an earth(|uake ? "

* Lyell, Principles of Geoloçnj, 12ih edition, p. 16 L

298 B. KOTO: CAUSE OF THE GREAT

The cause.'i of mrtlKiiiah's. — A popular subject with the men of
science of all a^'es has lieen the causes of earthquakes, upon which
much has been written, Imt of whi(;li little is yet known. As earth-
quakes are, in one place or another, of daily occurrence, especially in
the nijiiiinul circle which sej)arates the northern from the southern
hemisphere, and as the dejjths of curiosity are stirred up in the minds
of people who have unhapj)ily experienced the st;'.rtling treml)lings of
what is usually looked upon as the symbol of fixity — all sorts of ex-
planation have been offered as to their origin; and hence the world
has had, both in past and recent times, the misfortune to see the
sporadic a])])earance of monstrous theories on the subject. It lies,
howe\'er, beyond my present limits to give here the various views as
to the causes of earthquakes. This has been already done by Franz
Toula in his " Ueher deft (ie(jemrärii(jen Strnul der Erdhehenfra(ie,'' and
readers are referred for details to that small treatise.

One of tliem is, however, ^\■(^rthy of mention, as it was for a time
held in much favour in Europe. Rudolf Falb, the editor of the ]io])ular
astronomical j(3urnal, " *S'//7?/.s," is the chief su ])porter of this sideric
hypothesis.* A cosmic Ixxly, esjiecially the moon, is, according to him,
able to exert its influence upon the imcJevs of the terrestrial globe in
causing a, tide in the interioi- and simultaneous contracti(Mi of the earth,
and by so acting may induce a subterranean volcanic ex])losion which
results in a shake on the surface.

AVhile the Austi'ian joiu'nalist is engaged witli his favourite idea,
but more in popularizing it than in establishing it on a firm scientific
basis, we see in another direction an endeavour inade to inquire into
the causes of seismic phenomena through researches on the formation
of mountains. The study in this direction is an effort to bring
together into scientific shape the facts ascertained through detail-

* Gnindz'Uje zu einer Theorie iler Erdbeben uml l'ulkiinmisbriielu', i'S'6'.9.

EARTHQUAKE OF CENTRAL JAPAN, 1891. ^99

ed studies of individuîd earthqnuke«, and ;i comparison of the results
(obtained tlierefnjiu with the facts of the u'eolo^ical structure of the
region concerned. The chief merit in this Hne of study is (Uie laro-ely,
at least, to the Austrian geologists, Suess, Floernes, and lUttner. The
last-mentioned author gave a finishing l)low to the fantastic liyjMjthesis
of Falb, in liis \V(jrk on the earthquake of l>elluno, in 187o,*

Although we are as yet not in a position to be perfectly clear on
the dynamics (rftlie formation of mountain-ranges, still we are already
in possession of a certain knowledge on this subject through the study
of the Al})s. Long ago, Eiie de Beaumont saw in the origin of nioun- •
tains a radial, e]e\'ating ])ower, but to this C. Prevent made strong
objections. The latter taught us that tlie elevation is only the effect of a
depression of neighbouring regions; and the same view is advanced in
the works of Le Conte and of Dana, in a more t)r less modified shape.

Suess was led by his investigation of the tectonics of the Alps,
to express himself to the effect that unequal contraction and the hori-
zontal shifting of the earth's crust resulting therefrom are the cause of
foldings of strata.

Again, in his '^ EntstcliiuKj lier Alfx'ti,'' Suess says that all moun-
tain-ranges are (rf one-sided, unsymmetrical structure, the jjrobable
explanation being thaï tliey originate at the mai-gin of a great depres-
sion which exerts a horizont:d, lateral pressure. The concave side of
mountain-chains on which they face depressed regions we may
naturally expect to be much disturl)ed and ruptured; and seismic
activity and volcanic eruptions are usually manifested jxu-ticularly at
this weak point. Professor H. Crednerf holds the same view about the

* lieitrruje zur Kentitnixs des Krdhelk'ns ran lU'llunn. Sitzlx^r. d. k. Akademie d. Wissea-
schaften. 69 Bd., 1874.

t (a) Bas vorjtlandisrlii' Knlhcheii vom 23 Nov., 1875. Zeitschr. für die ges. Naturwissen-
schaften. 48 Bd. 1876. (h) Das dippoldiswahh'y Erdbeben von .5 Oct., 1877. Zeitschr. für die
tCHs. Natui'wissHnsfhaften. 50 Bd.

300 Lß- KOTO: CAUSE OF THE UREAT^

earthquakes of the Vogtland and the Erzgebirge, with regard to
mountain-structures. Hoernes tells us in the concluding- remarks of
his paper,* that earthquakes may take origin from different causes;
at one time, the falling in of subterranean ca\'ities, though very
rarely, and at another, a volcanic explosion, may bring about locally
terrible convulsions; hut hy far the greater nwnher of eartliquahes and the
most terrible ones are the direct outcome of the process of mountain-making.
Under the last category are included those shakings whose frequency
and seismic area are more or less closely connected with certain lines,
upon which the shakings are repeatedly observed. As they appear
to have some direct relation to the activity of mountain -building,
Hoernes gave them the name of tectonic earthquakes.

Having given a general retrospect of views as to the causes of
earthquakes, I. may now proceed to the immediate subject of this
paper, which is divided into five sections, as follows : —
I. Dislocations.

II. Geology and topography of Mino and Owari.
III. The great earthquake of the Mino- Owari plain.
£V. Various views as to the origin and cause of the

earthquake.
V. Relation of the great fault to the recent earthquake.
VI. The course of the line of the great fault that caused the
earthquake.
VII. Concluding remarks.

* Erdbeben-Studien. Jahrbuch d. k. k. geol. Eeichsanstalt, 28 Bd., p. M8. '

EARTHQUAKE OF CENTRAL JAPAN, 1891. ßQ]^

I. Dislocations.

Whatever may be the cau«e, whether depression or unequal con-
traction of the earth's crust, the formation and structure of mountain-
ranges are surely due to the folding, rending, and Assuring of strata.
Therefore it is not entirely out of place to insert here some considera-
tions on the topic of dislocations, which Professor Suess has ably
sketched out in his " Das Antlitz der Erde^

" Die sichtbaren Dislocationen in dem Felsgerüste der Erde sind das
Ergebniss von Bewegungen, welche aus der Verringerimg* des Volums unseres
Planeten hervorgehen,^' A stress originated in this process may be
resolved into tangential and radial components. The first is
horizontal, folding and shifting the mass; the second is vertical, often
causing a large tract of land to be depressed. The tangential com-
ponent is more superficial, pressing up the strata into mountains; the
radial component acts more profoundly in the interior of the crust,
and as a rule volcanic explosi<3ns accompany the dislocations due to
it.

«) We begin with the tangential movements of the lithosphère.
The simplest result of a horizontal thrust of any superficial part of the

* Every theory which lias hitherto been proposed to accoiant for the elevation of moun-
tains and the folding of the stratified rocks forming the earth's crust hinges finally on changes
of temperature. Thus the tangential force generated in the rigid crust of low temperature
by the cooling and shrinking of the earth's nvicleus has been invoked to account for the
cruuipling of the crust into mountain-ranges ; the crumpling skin of a dried ajjple being the
stock illustration. In this case, the force called in is continuous contraction by loss of heat.
The theory which Mellard Read has elaborated is the one dependent upon alteration of
temperature in the crust, contraction and expansion both being agents of viplift and lateral
pressure. Mellard Read : Origin of Mountain-ranges by Sedimentary Loading and Cumulative
Recurrent Expansion.

302 ^- i^OTÖ : CAUSE OF THE GREAT

crust is the productiou of u series oi' folds with alternating <reosynclinals
and geanticlinals ; the crests of such wa\^e-like f(jlds corres])ond to
longitudinal uK^untain-raiiges, the intei'vening troughs being longitu-
dinal valleys. The direction in which the force acts is at right-angles
to;the strike <jf the saddles, or to the axis of a intjuntain-chain. Fold-
ing such as we have mentioned of course inv(jlves tilting, and all the
different forms (jf inclination haN^e l^een described as occurring' in
nature. We may cite, as an example of such, a, chain of the Samba-
gawan schistose rocks that stretches from the city of Tokushima to
Cape Sadano-misaki in the Island of Shikoku; while the valley of the
Yoshinogawa, which runs |)arallel with that range and discharges its
waters into Linschoten Strait, may Ije taken as the model of a
longitudinal valley.

When the stowing (jf mountains ^and the puckering of beds are
carried to a certain degree, the limit of elasticity of rocks will be over-
stepped, and one effect of this may be that the beds of the upcast side
are l)odily shoved over those of the downcast side. A set of such
" cree])s " (IIVc'^.sc/) will produce what is termed the overlaj) tault or
Schupjx'nstriiciiir. At the same time part of a mountain may be dis-
lodo-ed alono- a fissure runnini»' i)arallel to the axis and strike of a rido-e.
The movement of a complex of strata in such a case along the line of
loii(fitmli}ial or periplicnil fault will cause a lotnjiimliiial ('artlKjiiah'.

If the liorizontal force do not act with equal intensity over the
area affected l)v it, one part will be more strongly compressed by it
than another, and will consequently he pushed forward along a fissure
that is directed at right-angles to the axis of a mountain. In this
way, parts of a> mountain-chain may be thrust forward along sets of
transccrxe fissures. At the same time the strata will suffer downward
displacement, and such a dislocation be accompanied by what is called
a transverse eartlupiake. That the great earthquake of October last,

EARTHQUAKE OF CENTRAL JAPAN, 1891. 3()3

shcjuld be counted among this class of convulsions will be argued
out in detail in the sequel.

ß) As we have already said, the stress proceeding from contraction
of the eartli resolves itself into tw(j elements, of which one acts more
or less in a tangential or horiz(3ntal direction, while the other works
vertically, and dislodges a large tract of land into a caldron-like de-
pression. Of tlie dislocations due to the tangential component, we
have already given a general sketch. Now it will l)e clearly apparent
that, while these horizontal shiftings are going on, especially along
transverse faults, some parts will receive a passive movement in the
vertical direction, resulting in a local dovvnfidl of beds and in landslips
on a large scale, as if also the radial component were working from
great depths.

Tlie (jemiiiie radial movement should not he confounded with siicli a
local depression of strata into a holloiv in the superficial part of the crust,
as that of Fujitani in tlie Nco ralleij, which, up to the present, is supposed
to hare been the sole cause of the earthquake that convulsed nearly tlie
ivhole of Southern Japan in Octoher, 1891. True radial displacement, of
which we are now speaking, is the downward movement of an im-
mense tract of the solid crust, and its effect does not usually come
clearly into relief in a country, except in a less disturbed bed like
that of the Plateau of Colorado.

The caldron-like dej)ression resuhing from vertical displacement,
topographically known as a basin, can be found in various locali-
ties along the inner or Japan-Sea c(^ast of the Main Island, which
curves down from the Ivuriles (Chishima) to Kyu-shû, with its
convex side towards the l*acific Ocean. Here, as on the Tyrrhenian
<-oast along the inner side of the Apennine curve, we find, with Dr. E.
Xauinann*, a number oï depressed basins, each having a gigantic

* Ueber den. Ban unci die Entstehung der japanischen Inneln, p. 74.

3Q4 B. KOTO: CAUSE OF THE GREAT

volcano in its centre, such us Iwaki, Moriyoshi, Chökai, Ga«san,
Daisen, Sambé, and Aono.

Nearly at the middle of the Pacific side, a notable indentation of
the coast-line forms the liay of Ise, whose northern prolonuation is a
kettle- like depression. This is the low plain of the twin-provinces of
Mino and Owari, which was the scene of the disaster occasioned l)y the
subterranean convulsion in the autumn of 1891. This flat has the
appearance of a basin, circumscribed on all sides by walls of moun-
tains, except at its rim on the south, which is, as just stated,
open to the Bay of Ise. The west, nortli, and north-east are l)uilt
up of Palaeozoic formations, while the mass of granites of Mikawa
lies on the east.

Mr. Kochibe, of the Geological Survey, made hioini hi Ins
ojjicial report Ids view as to the cauae of the late earthijuake, irlncJi
is based on the assumption that the ahorc-moilioned plain is a (jeolocjical
sag or ' Graben- Depression,' as Prof. Suess would say. He supposes
that beneath the surface a number of fault-lines run north and south,
a.nd also east and west, and that in consecjuence of the downward
movement of strata interposed l^etween the planes of fault, displace-
ments have eventually formed the present plain ; and he also beheves a
paroxysmal sliding of a complex of rocks on these old geological lines
to be tlie actual cause of the earthquake. Our geological knowledge of
this part of the country is as yet very imperfect, and some time must
elapse before we can expect to see any successful attempt to estaljlish so
daring an hypothesis on a tolerably safe scientific basis. So nuich in
technical tre;itment of dislocations.

EARTHQUAKE OF CENTRAL JAPAX, 1891. 305

II. Geology and Topography of Mino and Owari.

We have already pointed, out the geographical situation of the
provinces Mino and Owari on the ïokaidô, lying nearly half-way
between Kobe and Tokyo. The picture.Mjue Lake Biwa with an area
of 715,5 square kilometres, lying to the eastw-u"d of Kyoto, is separated
from the neighbouring Mino-Owari ])lain by the meridional ridge of
Suzuka. The range is mainly built up of Palaeozoic formations, with
a subordinate mass of young biotite-granite rising to a considerable
height, and over which the old road of the Tökaidö winds up
through the well-known Pass of Suzuka (373 m.).

The l^xht'ozoic foianations are chiefly composed of multifarious
alternations of a greyish, medium -graniikir, arkose sandstone, p.ncl
imperfectly fissile, blackish clayslate ; with these are associated
hornstone and lUuliohirimi slates (Profile n — h, PL XXYIIL). All
these thick C(3mplexes are sterile in well-preserved fossils, and as yet
no detailed geological studies ha\e been made of them; so that
we ;ire at present obliged to call them simply by the vague term of
tr:insition foruKîtions. There are, however, a few bands of com]>'!ct
limestones inserted between them, which nlford tolerably abundant
organic remains. These fossiliferous limestones have already been
m;ide the subject of a special study * l)y the hite C. Schwager ^^llo
discovered in them many well-characterized petrifictions, viz.: —

FusuVuKi /(ipoiiica Gümbel.
,, eorilix Schwager.

Schirdficn'iia \ frhffki Geinitz?

,, emticiilifem Schwager.

FiisiiI/NcJIa s]).

* Ridit!ioiVn, Cliina, IV. Bd.

306 B. KOTO: CAUSE OF THE GREAT

LuKjulijia sp.

Tctniitid.'^ cotiica FAweviherjs.

Ettilotlujvd crass(( Hradv.

CUmncammiiKi profeiita i>ch^^',lgel\
Dr. Gottsche* added to the above list the followino' forms :

Arcliacocidans, Potcriocriuus^ Voitacr'nnis, Farosites, ? Ciiatlio-

plijlUimi, I'leiirotoiiuina, ? 3Iiin']iisoNi(i, J'x'lh'rojtliON ap'. hiiilciis

Sow., 3 Fusiilina, 2 Selumfifrina, ßjfidofhym, TrocluiinmiHa

nnd Textilaria.
From Avhat has l)een given of tlie organic remains, it is clear that
the limestones are of the Carboniferous age, and the tliick complexes
occurring together with the calcareous beds must represent partly or
wholly Palaeozoic formations. These Primary strata di]) towards
the north-west, and their strike is north-south. The ridge of Yörö
((S40 m.), which is a detached mass of the Suzuka, rises precipit-
ously from the plain lielow and forms the western boundary of the
lowland of Mino and Owari.

As may be judged from the direction of the limestone outcro])s,
in the rectangular geological map, Section Nagoya, t the whole
Primary formation seems gradually to change the strike at the north-
west ('(^rner of the ])lain, and the well-known fossil l(X';dity of Akasaka
is just at this turning ])oint (PI. XXX.). Afterwards the strike
shifts a little to the n<^i'th-east, then east to west, and finally, at the
north-east corner (^f ^lino, the Paleozoic beds proceed directly in
a north-easterly direction far into the mountainous province of
Hida. On the east we find the massive mountains of Mikawa, largely
composed of granites in which at times hornblende, at others biotite
or moscovite, occurs as prevailing component. The granite, frequently

* Zeitschrift der cTeutEchen geolog. Gesellschaft, 18S t.
t Published by the Geoloofical Survey of Jajjau.

EARTHQUAKE OF CENTRAL JAPAN, 1891. p)()7

showing gneissose structure, t;ikes up large geological blocks or
" ScliolJcH " of gneiss, gneiss-mica schist, mica-schist and also am-
phil)ole-schist, which may l)e classified into Laurentian, and Fp])er
Archaean (tlie Takanuki and the (lozaislio series). The writer has 1)een
recently engaged in a special study of tliesf antnent rocks, and the
results will l)e found in earlier pages of this voliune.

Thus the twin ])rovinces are on three sides bounded by masses of
mountains, and in their very centre lies an extensive populous plain,
Avith an area of not less than 1,051 square kilometres or 68 square
ri. The general as])ec.t of tlie plain, which inclines slightly towards the
foot of the Yöi'ö ridge is monotonous and flat. It is covered with
a net-work of rivers and artificial canaJs which, owing to the special
orographic condition c^f the low-lying tract, mostly concentre at the
western margin (see Map, PL XXTX.). The largest of the rivers is
the Kiso-gaw^a, which starting from the dense impenetrable forest of
the Kiso-kaidö, is fed by several tributaries before entering the
plain, wdiere it joins with the Nagara and Tbi. These confluent
streams branch off at one point and reunite at another, discharging
their waters at the head of the IJav of Tse. near the port of Yokkaichi.

The head-w^aters of the Kiso drain the granitic area, of the
]H'imeval forest of Shinano, and the swift current, carrying with it an
enormous amount of detritus and sand, unloads its contents in its
lower course. The formation of the ])]ain is, I think, largely due to
the sediments of this river. The lowland of Mino and ()wari is usually
spoken of as having been once an immense swamp, since converted
to the present paddy-l;nid within historical finies, and having as the
last remnant of its former grandeur the Lake of Shim(i-ike, at the foot of
Yörö. [t now stands foremost in I'ank among all the rice-])roducing
districts of Ja[)an, and supports hun<lreds of thousands of people,
Nagoya, Gifu, and Ogaki being the chief centres of its commen/e.

308 B. KOTO : CAUSE OF THE GREAT

Although the story of the wide marsh seems to be n ofrent
exaggeration, still we see in it some germ of truth ; for, if all the
artificial canals and dams were to he removed, tlie present fertile
land would in a moment he nothing better than a moor. It is these
dams and the drninage system that suffered the greatest damage by
the last earthquake, so thüt to reconstruct them in their former state
will cost the people an almost incredible sum. The length of embank-
ment and mont, surveyed officinlly for repnir. is not less thnn 510,5
kilometres.

There are strong reasons for believing thnt the low-lying tracts
experienced the shocks to the greatest degree, not that they were at
the epicentrum of the earthquake, but liecause of the s;mdy nature of
the ground. The soil wliich makes u]) the greater jMirt of the paddy-
land, especially the eastern, severely damaged 1)y the last earthquake,
consists of loose, incoherent, fine sand ^vith but little clayey matter.
This soil T consider to have been formed out of the sediment of the
Kiso-gawa.

The rivers, Nagara and Ibi, take their origin high up in the
Palœozoic mountains of the northern border, and the rocks u])on which
they exert their denuding action are sandstones, hornstones, and
clayslates. The sediments are therefore more or less clayey and heavy.
The land formed from tlie silt of these rivers occupies the western part
of the plain, through which they make their way to the sea ; and this
is the seat of least damage by the late sulvterranean convulsion.

The North of Mino, as already briefly stated, is a mountainous
district, consisting mainly of Palaeozoic fn-mations. A cordillera
runs from south-west to east, and then north-east, proceeding di-
rectly through the province of Hid;i to the volcanic group of Hakusan
of Kaga, the Japanese Alps (Pis. XXIX., and XXX.). It is the main
divide which separates the river-systems of the Pacific and the Japan

EARTHQUAKE OF CENTRAL JAPAN, 1891. 3yC)

Sea. Beyond the mountaiii- ridge lie the provinces of Echizen and
Kaga, where the Mesozoic formation is extensively developed, and later
on has been intruded into in places by masses of Tertiary eruptives.

A plain of consideral)le extent, ^^■orthy of mention here, is the
basin of the Kudzuryù-gawa, in the centre of which lies the city of
Fukui. This region felt severe shocks during the late earth([U;ike, and
suffered calamity surp;issed in extent only by that felt in Mino and
Owari. During' winter-months the icy winds from Siberia, crossin»- the
waters of the Japan Sea, blow strongly against the ridge, and copious] v
precipitate moisture in the form of snow. This part of the country
presents a dreary aspect, and is untrodden land within the heart ot tlie
Main Island. It is rarely visited by geologists, but Mr. Kochil)e, du-
ring his reconnaissance survey, once crossed the range in going north-
ward from (.Trifu, through the Neo valley, which is well known since
the last earthquake, to Echizen, over the pass of Haibôshi. The line
of section, c — </., PI. XXVIIL, is constructed from his tield-sketch,
supplemented by one by myself.

This section is one drawn nortliward from a ])oiiit south of
Yamaguchi up to the top of liakusan ((xongen-yama), for a distance
of 27 km., and goes obliquely through the wIkjIc Pakeozoic formations
of the North of Mino.

Just at the entrance of the valley near Yamaguchi, a bed of
hornstone is exposed with a l)and of limestone in it which encloses
abundant remains of crinoids and foraminifera. This com])lex .is
followed to the north and oveilaid l)y skite with the strike nearly cast
to west ; then come hornstone, sandstone, and again slate, and so on,
with northerly dips usually at very high angles. The lithological
characters are rather constant throughout the whole valley, and the
multifarious alternations of the above-mentioned rocks constitute the
Palœozoic formations of this district. The strike of the rocks remains

310 ^- koto: cause of the great

the same till we come to Kiré, whence it changes very slightly to the
north-west. The youngest and c(jnsequently the northernmost of
the series is the hornstone of the upper Neo, where it ahuts upon
the (jranite-porphyry of Hakusan (Hakusan Mayeyama). Near
the point of contact an intrusive rock of the character of I'.onthlciule-
porphijnj is pressed up through the stratified complex.

The petrographical characteristics of the porphyries are here
given : —

«) Granite-porphyry, — This is a rock wLich presents peculiarities in many
respects, and is of wide distribution throughout Japan, especially in the liighlands
of Hida. It was once called granite, then diorite, but now goes generally by
the name of porphyrite in all the Geological Survey maps, It is, however,
not a typical mica-hornblende-porphyrite, since it is of granitic structure, and con-
tains moreover a large quantity of monocliiiic feldspar. On the other hand, the
name diorite does not suit it. It resembles a biotite-hornblende granite most
closely both in mineralogical composition and in structure ; but the presence of por-
phyritic crystals precludes its being classified as that. It is a greyish-white, mediums
granular rock of dioritic aspect, decomposing into angular fnxgments, like chips of
a liornstone-mass. Phenocrysts are scarcely distinguishable in hand-specimens, a-
the component minerals are nearly of the same size. Feldsjna- and honMende enter
largely into its composition, and, when examined under the microscope, quartz and
biutite are observed, together with »uKjnetite., epidotc, zircuit, titanite, and (qmlile as
accessories, the last one being especially characteristic of this rock.

The feldspars are the dominant ingredients, and fall into plagioclastic and mono-
clinic varieties. Which of the feldspars is present in larger tj[uantity is not easy to
say. iSpeaking generally, the porphyritic, tolerably idiomorphic crystals are mostly
but not exclusively plagioclase, with the well-developed zoning which is the charac-
teristic of rocks of a porphyritic structure. The feldspars are mostly oligoclase,
sometimes schillerized, extinguishing light at about 18° with the twinning sutures,
and with their centres frequently kaoliuized over a definitely marked area with
patches of chlorite, the surrounding zones being apparently untouched by weather-
ing. The feldspars are the only components that deserve the name of phenocryst.

The rest of the mass is a granitic aggregate of feldspars mostly orthoclase.

EAUT11(,>UAKE OF CEXTKAL JAPAX, 1891. ^H

and of lionibleude, biotite, and (juartz. The honiblonde, appearing macroscopically
as a porpliyritic ingredient, is really an accumulation of amphibole and biotite, and
these decidedly belong to the second generation of crystals. The irregular plates of
hornblende, deeply indented by grains of (j[uartz, and interlarded throughout by
prisms of apatite, arc of a deep bluish-green colour and pleochroic. The brown
librous biotite has usually grown with amphibole into irregular tufts, and with them
clumps and crystals of magnetite are commonly found. In one slide examined
botli magnesinm-bisilieates arc greatly decomposed into a green übrous mass, finally
changing into a chloritic substance. In this case a large quantity of dust and
numerous crystals of magnetite, together with leucoxene, have settled within the
confused aggregates, accompanied by secondary epidote.

The feldspar of the general mass is not striped, and is much more decomposed
than the phenocryst. Its form is imperfect, being conditioned by the mutual
disposition of the same species and of the magnesium-bisilicates. The quarts is
present only in small quantity, and is irregular in its form, having filled up the
interstitial spaces left by other ingredients. It is of course fresh, displaying the
usual vivid chromatic polarization, while the other components are more or less
decomposed, and conse(j^uently appear dull. Well-finished crystals of it arc nowhere
observed. It is interesting to note that the quartz contains abundance of liquid and
gas-inclusions, the former often holding dancing bubbles and also s)iitdl viihes, prohahbj
of soiliiiiit-cliluride. Glass-inclosures are so far not observed.

Zircon is found in the combination of I* and x V, and titanitc is found in
irregular grains. Apatite is plentiful ; its cross-sections are licxaijons irith allenudchj
tniiicdU'd canu'is, the longitudinal sections being lath-shaped exactly like those of a
tourmaline. Neither the transverse nor the longitudinal section of the apatite
becomes totally dark in any position during complete rotation upon the stage. Its
crystals contain, especially in their central portion, a large number of gas and li(juid-
inclusions with spontaneously moving bubbles.

Another slide, made of a specimen from the same locality, presents characters
somewhat deviating from the above, in respect to structure, the general mass being
for the greater part made up of an intimate intergrowth of quartz and feldspar in
// 1(1 (jrec form. The general aspect of our granite-porphyry seems to have a close
resemblance to the rock, called by v. lUchthofen,"' the Corean granite, from Kauli-

* "Cliinu." Off. 11. «chwerdt, rittersuchunn über Gesteine der cluwj^^isdwn rrocin.cii Scliaii-
tuiiij und Hnntuiiij. Zi-itacUr. d. d. geol. Clesell. Btl. 38, p. 211.

312 B. KOTO: CAUSE OF THE GREAT

mon, the Gate of Corca, sitnatcd at tlic sijutb-east coi-nev of Liau-tang.

,?) Hornblende-porphyry. — This is a hovnblende-diorite-porphyritc, of an
ashy-looking aspect, with tolerably large (üinin.), Avcll-tlefined crystals of honihh'iidiiiH
the povphyritic ingredient, seemingly forining dykes in the Palicozoic complex. The
general mass is a greyish, tine-crystalline aggregate, in which no other component
except the above-mentioned hornblende is to be seen. The anjphibole-phenocrysts
arc of two varieties ; the one is in well-defined prisms of compact texture, with the
clcavcige face porfejt and sluwing a sub-metallic lustre ; the other is rather greenish
and fibrous with imporfe^-t crystallographic outlines. The distinctive features of the
two become more pronounced, when viewed under the microscope.

The compact hornblende is of a deep-brownish colour with dili'ereut tones in
centre and peripher}', and is bordered by greyish and blackish granules of
li'iicoA-c'iic. Its pleochroisin is distinct ; its outline is tolerably regular, and twimied
in that shape which was formerly considered as anomalous twins whose plane of
contact was supposed to be the prism goP 2 (120). i The other variety is of a
yellowish-green, line, parallel-librous texture, resolving oftentimes into chloritic
patches. A large (quantity of magnetite is present, being scattered through the
Avliole mass.

The rest of the rook is holocrystalline, being built of lath-shaped fehhjxir,
chloritic honihleiuh; and black iron-ore with borders of leucoxcne. The greyish, more
or less decomposed feldspar is simply or doubly twinned. There seems to occur
another feldspar Avhicli is of rather larger size than the other, and of irregular
outlines with no signs of a twinning structure. It is probably orthoclase. Allo-
triomorphic angular i/Kart: fills up the interstices left by other ingredients. It is
present only in small (juantity, and shows a greyish tinge between crossed niçois
with undulatory extinction. The c[uartz contains abundance of li(|U id-inclusions with
spontaneously mj\ing bubbles. The general colour of the ground-mass is grey, on
account of the presence of a large ainjunt of leucoxene and chloritic matter, with
an aggregate of more or less decomposed, greyish feldspar.

As ni:iy bi3 seen i'roiii the sketch in i*lule XÄX., tlie strike of the
PiiUeozoic form.itions changes its direction in a mo;-;t peculiar manner.

t Becke ; T^icheraiak's miuoralu^-. nud peirogT. Mittli. Bd. IV, p. 305.

EARTHQUAKE OF CENTRAL .TAPAX, 1891. 0^3

At. first, it points a little Avest of uortli as in llie Suzuka rido-e. then
tnrns to tlie nortli-oast at Il)uki. Afterwards the strike is due east-
west, then again it iniperceptiljly deflects towards tlie nortli-east,
retaining- the dip always on the left side (compare the profiles a—]),
c — d, n. XXVTir.). In fact, the course of the direction of strike
makes a sigmoi(hd cur^•e, from which it is eas}^ to concei\e tliat the
strata must liave sustained stress from ^.arious directions.

Under such circumstances the axis of the s-uhHes must lune recei\ -
ed an excessi\e twisting stress, and we may rcasonahly expect that (hi-
ring the movement the heds of rocks must ha\e gi\en way to fracture
somewhere within the mountain, like the grou]> of tissures in a pane of
twisted glass, as experimented u])on l)y Da.uhrée.* There are. \ think, a
numher of such weak, ü'eoloii'ical lines in this reu'ion as Ihe eflect of
torsional movement ; the f )ur valleys, Tokuno-yama. Xeo, ^lugi, and
Itatori may he taken as (^f this class of dislocation, upon which the
atmospheric ao'cncies have exercised their denudinu" acti<^n durin"' the
course of ages in ])roducing the present deep ra\ines. As may be
clearly seen from the sketch given in IM. XXX., the courses of the
ahove-mentioned valleys are to]eral)ly regular, running parallel to each
other from north-west to south-east, and thus sti'et(hiiig from the
Kisogawa to the pro^■ince of Echizen,

There seems to occur, besides tlie ;d)Ove mentioned parallel lines,
a numher of fissures at right angles to the pavachii^e^. These trans-
verse clefts, or to use Dauln-ée's word, (h'((clas('s. may he traced in the
zigzag run of the valleys. Tin' rallciis in flic Xortli of' Mino t]\ereforr
j)resnif xiich rnjuhivilioi in tlii'ir coitrxe, tlial llwij cttn In/ no mrans Ix' atln-
]t)if((hJ(' to tlie rc'sult of mere crosirc (KjfNcics and tlicir origin must be
ascribed to deep-seated discontinuitii in tlie eartli's crust (P. XXX.).

* Si/ntht'ti>fclit' Stiidimi :ur Espci-imcntdl-GeoJociic, p. 230.

314 If'- T^*^TÖ: CAUSE OF THE DT^EAT

IIÏ. The Great Earthquake of the lYlino-Owari Plain.

It was on Oetol)er ^Sth, 1891, at (îh., :57'. H", when the first
shock of tlie great eartli([Uake was experienced, that l)eing' far and
away worse than <any of the many which succeeded it. It l)rought
down tlie liea^-y tiled roofs and stone-laden thatches, and in ;i
moment huried thousands of living people l)eneath them. At
Ogaki, (Jifn, Kasamatsu. Takégahana, and many otlier places, im-
mediately after the first great shock>!, fires bi-oke out amongst the
ruins, and many who might otherwise have l)e?n extricate<l were
bnrned to death.

In the alhivial plain, especially in the neighbourhood of Xagoya,
the ground was riven with myi'iads of fissui'es ; small mud volcanoes
were thrown up along the Shönai-gawa, comparable to the sand
craters of Achaja, in (Ireece ; and for the length of a inile, near
Biwasliima, a suburb of Xagoya. numerous fractures made their
appearance in the banks of this river (Fig. -. V\. XXXI.). Here
too a very strange thing happened. There Avas a large bamboo
grove and a few pine trees, just at the west side of the embankment,
and this slid bodily some .s/.t7// J'crt back, the bamboos and trees
remaining upright (Fig. 2, I'l, XXXIL). In this figure will be
seen a thatched roof fallen intact, and it was in this manner that
most of the farmers' houses, which so tliickly covered the Mino-
Owari plain, gave way, and the country became dotted over with
tlieir roofs, which from a distance presented the a])pearance of gigantic
saddles (Fig. 1, Pi. XXXI.).

Going northwards from Xagoya to (Jifii, we find a series of
villages, one running into the next; that is to say, there is a
nearly continuous street of ten r/, or more than twenty miles, in

EARTHQUAKE OF CEXTCAL TAPAX, 1891. p,]5

lengtli. The rows of houses were tlirowu over l)y tlie sliocks, nnd
these twenty miles of iv^nd liecame simply a narrow lane between
tAvo intermina1)]e lieaps of délu-is (Fi,u'. 1, IM. XXX 11.).

Gifn, tlie provincial capital, was for the greater part over-
thrown, and then burnt l)y fire. Ogaki, once the resident t(^wn of
the Princes Toda, seven miles west of Gifu, was entirely levelled
with the ground, and tlien also consumed by lire. Kasamatsu,
just ori tlie north ])ank of the Kisogawa, suffered the same fate,
and all that was left of it was a reddish coloured expanse of tiles
and rubbish. The fite of Takegahana was as bad, or worse.

What has been stated can convey l)ut an imperfect idea of the
destructive woi'k done by the late great earthcpiake. Still greater
convulsions happened in the UKTuntain district of the Xortli of ^[ino,
traversed tor a distance of more than forty miles by the line of
fault, tlie birthplace of shocks, where all things were destroyed that
happened to lie in the proximity of the great throws of strata, to
which I shall have to retnrn in the serpiel.

Professors d. ^lilne and W. K. I)nrton, of the Imperial Uni-
versily, have given a lively account of the subterranean convulsions
in " Th(' Great Eartlnpia],')' in Japan, 1801,'' illustrated with twenty-
nine permanent-])hotographic plates in hondoir size, well jna'nted l)y
Ogawa, and the ])receding statements relative to the devastations
are mairdy taken from this excellent work.

The most dreadful e:u'thquakes within memory were the cata-
strophes of l(S54-55, well known among us as the ]'Jart])qiiah'.'< of
Ansei (/. ('., of the ' Ansei ' period), at which time Japan seems to ha^e
been the centre of universal earth([uakes. Poth years ])roved \Qvy
calamitous. Nice, Alexandria, and Turin felt more or less severe
shocks in 1854. During the following- year, 1855, X'ew Zealand,
on l)oth shores of Cook's Straits, was visited by a terrible earth-

o|ß B. 7C0TÖ : CAUSE OF THE GTIEAT

quake. A sliock was feit inudi :il)out the s;iino time at Truro, South
vVustralin. A iearfiil oarth<|Hako also shook tlic o]>])osito coasts of
the Sea of Maniiora ; on the 2(Sth of Fel)ruar\^, and in July of tlie
same year, a smart shock traNcrsed piirts of Switzerland, Lomljardy,
and the south of France.

In the first year of Ansei (1854), the wliole of Southern diq^nn,
especially the Island of Shikoku, was visited hy terril)le suhterranean
convulsions. The earth(|uake-]>ei'iod was a l(^nn' one. In the next
year, tlie centre of the suljterranean activity shifted more to the
east, and in the greater part of the ]\[ain Island, particularly over
the districts around the '"excellent and singular" volcano of Fuji,
towns arid villages were reduced to heaps of ruins hy most des-
tructive earth(piakes. Great as were the effects of the earth-con-
vulsions îit that time, the later catastrophe of Octoher. l<Si)l, seems
to ha\e heen far the more dreadful in intensity as regards ]\rino
and Owari, judging from the destructive effects of the disturhan^'e,
and the statements of peo])le who survived the event of the Ansei
period.

The j\[ino-Owari plain (OS srpiare ri) is one of Japan's great
gardens, covered with ri<'e fields and d(^tted with dumps of ti-ees
and with liandets ; rising from it on the north and south may he
seen the castles of Xagoya and Ögaki. This fiat supports a popula-
tion of perhaps 4,G8() ])er s<piare ri, or 004 to every square kilo-
metre, and is therefore the most densely ])eopled region in this
country, exce])t Sanuki in the Island of Sliikoku. Tlie meiso-
seismic area includes all this ])lain and the mountainous district
of Mino and Echizen. J>y the disturhance which occurred in this
portion of the F]mpire in Octoher, iSOl, the land liecame at once
a sea of waves, with movements greatly magnified on tlie soft
alluvial plain. As this lay near the origin of the disturhance, the

EARTHQUAKE OF CEXTKAL JAPAX, 1891.

317

■\v;ive8 were «hurt and rapid, and o\ertlirew towns and villages,
iissLired the ground, and ruined the strongest engineering struet-
iires.* According to the official returns, ahout seven thousand
people lost their lives, seventeen thonsand were wounded, and two
hundred scAenty thousand buildings were levelled with the ])lain,
while six thousand houses, less shattered by the shocks, were burnt
down Ijy fire.

4'he Ibllowiiiii' are the statistical accounts of daniau'c in the six
])roYinces, C(jnnng under the five Prefectures of Gifu, Aichi, Fukui,
Mive, and Shiga : —

Provinces.

W^ouuded.

Killed.

Buildings entire-
ly destroyed.

Ditto half
destroyed.

Burut.

Shattered
and burnt.

Mino

Owari

Mikawa

Echizen

Ömi

Miye

12,311

4,877
49
98
47
11

4,889

2,357

13

12

6

2

114,616

80,428

1,020

1,080

153

233

30,994

43,845

1,464

1,188

366

439

249

196

5,934

Total

1 7,393

7,279

197,530

78,296

445

5,934

The following three cases are selected as examples out of a long
table, t(j sIkjw to what degree some of the cities and towns suffered
in regard to both life and property : —

Names. Population.

Number of
ménages.

Wounded.

Killed.

Houses entire-
ly destroyed.

Ditto half
destroyed

Burnt.

Gifu

Kasamatsu

Takegahana

28,731
4,732
4,950

6,035
1,006
1,180

1 ,200
408
283

230

221
268

740

983

1,172

3,002

23

2

113
553

524

* The account given in this paragraph is based upon that contained in Milne and Burton's
Great EurtJiquake in Japan, IS'JI, already referred to.

318

B. KOTÔ: CAUSE OF THE GREAT

But this Avas by no means all the havoc wrought by the great
earth(|iiake. There was not a building in the entire rneisoseismic
area, and not one of the embankments whicli ha\e djeen con-
structed along the nets oi" rivers and c.-mals, tliat wholJy escaped
damage ; and. as T have alread}' said, it was officitdly repcn'ted that
the embankments calling urgently for rej^airs extended for loO ;/.
or 510 kilometres, while the length of the railroad demolished
was found to be 17 kilometres. AVhen steps had been taken to
estimate tlie loss, the amount of injury disclosed was found to Ije
much greater tlian had at iirst been recognized. The direct and
indirect damage done to the trade and commerce of Xagoya alone,
was calcidated to amount to 1.778,693 ijcn.

JsosfisTruHi lin^s

EAllTHCjUAKE OF CENTRAL JAPAN, 1891. 3^9

According to the Oßcial Gazette, the epicentral district, the
seismi(j ureca of the first order, whicli of course inchided Mini3 and
Owari, along with some jmrtions of the neighbouring ])rovinces,
extended over 11, 111 s(|uare kilometres, and over this area destruc-
tion of buildings and engineering works was well-nigli complete.
That of tlie second order reached as far as Kôlje on the west and
Shizuoka on the east, over an extent of 44,1)07 square kilometres.
AVithin this area several houses fell, walls, embankments, roads, and
bridges were ])artia,lh^ damaged, and the water of wells rendered
turl/id. That of the tliird order, within whic-h walls of houses were
fissured, clocks w^ere stopped, and crockery w^are, \'ases, etc., fell ofi'
shelves, embraced ö2.ol5 sipiare kilometres. Effects such as the
above were produced in the eastern lialf of Shikoku. and also in
Chügoku. and very nuich ihe same thing ha[)pened in 'l'ôkyû and
Yokohama. Lastly, disturbances were distinctly felt from Sendai,
in the north, to the west coasts of Kyushu in the s«juth, or over
an area of lo4.7:2:^ scpiare kilometres. This w-as the last or fourth
(jrder of seismic area. Altogether, the area shaken by this earth-
(piake in Central Japan will have been about 24o.000 square
kilometres, or more than <»()"/„ oï the whole extent of the I'hn[)ire,
as may be easily seen by a cursory glance at tlie annexed
chart.

The earth(juake, which lirought with it such disaster, seeuis
to have been of a paroxysmal nature, and one ihr which the in-
habitants were totally unprepared. Generally speaking, the fre-
quency of shocks was high during the month of Octol^er, 1891, and
the earth was by no means tranquil then at any time, especially
in the provinces of Musashi and Shimôsa. Seventeen separate quakes
had been already recorded 1)y the seismographs, previous to the 2Sth,
all however conliucd to the \icinity (^f Tokyo. Central Japan itself

320

KOTO: CAUSK OF THÉ GllEAT

showed 110 wiiins whute^■e^ of the cominjx disaster and there the
ground remained quiet up to the very moment when the sudden
catastrophe o\"ertook Mino and Owari.

Tlie Ibllowin^u' table shows the liuuerinu' of the after- shocks
of tlic great earthquake throughout the succeeding inontli. and for
several months after, minor shakes, which in Tokyo would he
considered stroni:*. continued to be ielt.

l>ays, 1891.

Kreqiieiicy of

earthquakes

in Gifii.

Frequency of
earthquakes
in Xagoya.

Kxces-! in

nuinbercf

earthquikts

in Gifii.

Days, 1891.

Frequency of

earthquakes

iu Ciifu.

I're'^ueiiey of
earthquakes
in Xagoya.

Kxcess ill

iiinnber of

earthquakes

in Uifu.

Oct. 28

102

126

-24

Nov. 14

29

12

17

„ 29

318

135

133

. 15

29

12

17

V 30

173

1)8

80

„ 1(3

28

18

15

„ 31

126

79

47

„ 17

21

15

6

Nov. 1

<»9

5()

48

„ 18

18

9

9

o

<)-2

80

(32

„ 39

17

4

18

H

Si

81

50

„ 20

88

9

24

4

78

20

58

„ 21

21

9

12

5

58

20

•A3

12

5

7

('

t)7

1(3

51

„ 28

28

9

14

,, "^

45

29

1(3

„ 24

18

9

9

Ö

42

18

24

„ 25

9

9

0

'.'

44

1(3

28

„ 26

15

5

10

„ 10
„ 11
„ 32
„ 18

40

88

12
5

28
88

„ 27

11

8

8

Sum-total

1.757

884

+ 873

40
85

7
18

88
22

IJouii to tlic

enil of
Mairli. 189-.'.

2.588

1.093

+ 1.495

It should l)e remai'ked that the ditference in number between
tlie earthquakes which occuiTcd in Xagoya Jind (nfu is \evy great
indeed, those in the latter amounting to nearly double those in the
former, and that from this it fallows that (xifu lay nearer to the
orio-in of the convulsion than X:io'oya. In the record of the i8th
of October, the day of the great event, an anomaly is apparent as

EAETHQÜAKE OF CENTRAT, JAPAX, 1891. 39^

to the frequency in tlie two cities ; but it is known from an au-
thentic source that while the seismic observations were re-opened
h'om Ih., â.V p.m. in <iiin, in Xaa'oya thev were started just al 1
p.m., the seismouTaphs previously set up liaving been compJetelv
shattered l)y the terril )le sliocks in the morninu'.

Down to the r^öth October, 1892. the number of earthquakes
recorded on seismometers run up to 2.092 in Gifii. and 1.170 iu
ISTag-oya, so that tlie excess of sepai-ate earthquakes in (n'fii over
those in Xasfoya is 1,822.

322 ^ FOTO: CATSE OF THE GREAT

IV. Views of Others as to the Cause oTlhe Earthquake.

After tlie o:irlh(|Li:ike seventl sngo-oslioiis as to its ])rol):i1)le
cause appeared in the newspapers. It will suffice to notice two
of these.

Since no volcanic outljurst had occurred it was felt by many
that the eartli(juake must have h;id its origin in the downfall
of a supcTÎncundjent inass of rock into some subterranean liollow.
Among those who ad\an<'ed suHi a view of the matter is tlie
diicf of the Meteorological Oljservatory in <iifii, ^Ir. Tguchi.
C onnnis.>;ioned by the Local (iovei'nment, lie visite*] the Xeo \alley
a few days ;dYer the e\ent, in order to make in\esfig;itions on
the sj^ot under Avhich lay [)rol)ably the seat of origin of the
shocks. The lacts stated in his i-eport are interesting and cui'i(^us.
The account of them I'uns as fjllows : —

At tlie foot of tlio mountain of Ilaku-san (Gongenyaiua). l.Sll m. liigli. ^vhic•ll
stands oil tlio border of the two provinecs of Eehizon and Mino, lies Fn.ii-tani in
West Neo-mnra, a division of tlie Ono district of Clifa rref('etare. It is aljout 20
kilometres or Ö rl froni the summit of Haku-san, with chains of hills rising on
two sides of it. In this place, some iifty years ago, there appeared two or three
lioles, measuring (! or 8 feet across. When stones were tlm^wn into these tissures
reverberations caused by their falling could be heard, it is said, for several mi-
nutes, from which it may be inferred that the hssures extended to a depth of many
hundred feet. At thirty-tive minutes past six. on the morning of the 28th of
October, simultaneoiisly with a deafening noise, enormous landslips in the two
chains of hills bounding the district took -place. Clouds of dust were thrown up
like smoke, to a great height, darkening the whole region, and in many places
the contour of the hills was perceptibly clianged. At the base of the liills the
consecjuences were not less marked. Houses and iields in the vicinity of Naga-
inine, Tenjindö, Midori, and Itasho were disturbed, l)ridges felh roads were obli-
terated, and tho general features of the landscape were radically changed. The

EATITHQÜ.UIF OF CENTRAT, TAPAX, 1S91. 393

1)0(1 of tlio vivor Non \Yas so nmeli alteivil tliat l'apiiU appearod in pavts of it
wliieh liad proviously bet^ii pools, aiul deep pools wore formed where shallows had
formerly existed. // inmhl si'fin us thutiiih thf canst' of thr lust r/utli(/ii(i/,-i' mis the
cniiiil'liiitl aivdij dj' h'tiji-tnni ut the J'not al' } Li/iUsu/t.

r>\ this local depression six seismic lines were formed radiating from this
very spot. The first line goes down the valley southwards, bifurcating close to
Itaya ; one branch proceeds south-eastwards through Takatomi, Akutami, and
Inuyama, the other follows the valley down through Tovama, Gifu, and Kasa-
matsu. The second line takes the southern course along the Avestern ridge of the
Neo valley. The third runs north-east over the Pass of Haiböshi to Ono göri,
while the fifth and sixth go right through ^Nlount TTakusan to Imadate göri, both
ill the province of ]']cliizeii. J'hns Inj n Innilslip <tf I'lijilani, tltr iji-cat eartlnpitthe
iras occnsioiii'il, tilt districts trari'jscd Jnj tjic uiinri'-riu'iitioinul si.r lines hciiKj sercrcli/
sJiif/:cii.

Dv. 'I. r. lîciTv.' <if Dö^hisli:! Hospital. Kyoto, ofierorl another
hv]iothesis in ex])laMatioii of* the cause of the earth(|iiak('. this heiiio-
the possible dependent relations of seismic distnrliances n])on the
electric condition of the eai'th.

J)i'. HeiTV. while staving" in O^'aki. experienced the >iC\ove
shakings and the distant tliundei's of the shocks, sometimes heard
for thi-ee seconds (?) liefore the tremors coidd lie felt. J If vas
proloiiNilhi tiiiiiri'sscil ifilli tin' ilioiKjltt llnit Nnlli/ii<i /*/// l]it' pmrcr of
i'h'clncilij rniilil proilticc l]ux rrsiilt. lie riujitnU mi lutrlhijixtl:)' slinclt'
(1.^ Iiiit (in I'Jiu-lric storm in tlw earth.

77/." laiMn ]]Wl-lij ^[ail, Xoy. 14. 1891. Yok<-ihauia.

394 1^- f^OTÖ: PAUSE OF THE TSREAT

Y. Relation of the Great Fault to the Recent Earthquake.

As introîluptorv to tlio nocoiint of the late oveiit. it seems
well to insert here a few notes of my own experience of the enrtli-
(inake of Knmamoto, of wliich 110 details liave as vet lieen li'iven in
anv forei^ii'n lan^ü'uage. (hi -Jnhj :?St]i. 18'^9, a r'mloii rnrtlnpKil.c
oceurird in ihr Nriijliltoiirliooil of Kiuuanioto. a jloun's]iifi<i ritti in ilw
hlaiul of Kiiü-Slni. I'eing entrusted by the ( reoJoo-ical Sar\ey
witli making a reconnaissance survey of the ])rovince of lîungo,
I was at tlie time engaged i]i that work in the vicinity of (ape
Sau'ano-sckij and thus liad the fortune to feel the sliocks wlii(h
caused nnuh damage to 1)ot]i life and property in Kumamoto. killing
fiftv-tliree persons and destroying about four liundred and sixty-
three houses. On receiving the intelligence of the cntastrophe in
the jieiii'hbouring ])rovince. T immediately started f)r the seenc of
disaster to examine its effects, and on my arri\al saw a large
nund)er of housi^s that had eollapse<l, and many others suppoi'ted
from filling by wooden poles.

The night of the ord of August was particularly distressiiig.
Shocks came regularly almost every hour, seemingly increasing
rapidly in intensity. At last, at about 2h.. iN' midnight, a great
earthquake, next only to the slioek of the week befoi'e, \isited
Kinnamoto. throwing the whole city, with its population of fiftv
thousand, at once into wild agitation, and filling the mouths
OÎ one and all with the (|uestion. where was the source of the
distur])ance.

To tlie west of the eitv of Kumamoto lies :ni extinct volcano,
locallv known as Xishi-yama. the •• western mountain." whose
effusive nature was then hardly suspected. Ascending it next day

EARTHQUAKE OP CENTRAL JAPAN, 1891.

ozo

I found it to be a typical volcano, with the somma, caldera, and
baraiico all preserved ; and at its centre, as is usually the case,
standing somewhat exeentrically, a sharp conical point, called
Ivimpô-zan (Kihö-zan). ^^'ithin the atrio are the villages of" Xoide,
Omonoki, and llirayani;i. Tracing the positions of the landslips
and of the destroyed luKises of the villagers. J hecaiiw coni'inccd
of iJw j'acl iJidl llicir are lira iiui'm lines, aloinj leliieh ihe hills ]iad
(jluled, lioKses heeit sliddered, (Oid tlieKjround convulsed und hrol'en into
chaos (see the map PL. XXXIII.). The first line runs from the
north-west along the Kawaehi valley througli fliravaina to the
small hut thriving town of Takasé. The sec«jn<l taking- the same
direction starts fnjm Xoide, at the southern foot of Xinodaké. which
seems to have been the acti\e centre, pnjceeds through iJaké down
to the southern slope of Arao-yama, and thence to the city of
Kumumoto. J between the two nearly parallel lines stands the Peak
of Kimpö-zan. The sec.'ond one sends off a branch line to the east
down to Tomonji.

These seismic lines, by which I mean the lines of fault, are
not favourably visible on the surface as in the case of the recent
catastrophe of Mino and (Jwari. but still I think I was able to
trace them by the fissures in the ground and along the slopes
of the hills. The fiicts that Ivim])ô-zan. the whole group beino-
generally called by this name, is volcanic. Ijeing made up of
augite-andesite ; that the faults though very indistinct aiv found
there in tliree lines ; and, lastly, that the seismic area was consider-
able, embi-acing the whole of Kyü-8hü, as well as a ])art of iShikoku
and the west end of the Main Island. — all seemed to me to point
to ilie conclitsion that the seismic disturhance in Kumamoto n'as caused
Inj a combined process of dislocation and an unsuccessful approach to a
volcanic explosion. Which of these icill hare been tlic main factor in

32() li- i^'OTO: CAUSE OF THE GREAT

producing tliis dreadj'nl calamiti), 1 am quite unable to mij. The les.son
I have learned from flu's plnjsical convulsion of Kumamoto, is tliat a
violent eartJi(fuile often manifests itself its actiritij along some narruu-
line or fissure witltin the eartJt's crust.

The residents of Tokyo ex|)erieiice yearly aljout sixty eartlitjuakes
■\vhieli are, as a ride, fortunately of a feel)le nature. These com-
paratively speaking languid earth<(viakes and such paroxysmal
varieties, as the convulsicjns i3f Kujnamot«^ and of Central Japan,
show some great différences between tliem in their effects, but tliese
are not fundamental. Terrible dislocation-earth((uakes present special
features of their own. not usually observed in sliglit shocks, 'i'he
seismic disturbance in the latter is not s(„) unifbi'nily felt o\er a
large area as in the Ibrmer. On the contrary, the sexerely shaken
area is common! v confined to a narrow zone, sav a, valley or a
mountain slope. In other words, strong eai'thquakes possess seisjuie
lines, as in the case of Kumamoto.

On account of this peculiarity, a series (jf towns and villages,
one running into the next, may be completely shattei-ed and laid in
ruins, while at a. shoi't distance on both sides damage is com-
])aratively slight. AVhile tra\elling in Mino and Owari after the
great convulsi(jn, 1 frequently heard ]>eo])Ie complaining of their
own deep suffering, and grudging the happy state of villagers just
a tew kilometres awav. I)i*. lîerrv* ])uts the matter well in saving'
that he witnessed all over the region (Mino and Owari) the peculiar
freaks and destructive violence of its (the earthquake's) course —
leaving houses untouched, passing under wIkjIc villages, and only
to appear again miles beyond with destructive violence. Even in
common earthquakes such as are experienced weekly in Tokyo,

* I.oc. cil.

EARTHQUAKE OF CENTRAL JAFAX, 1891. 327

such seismic lines or zonei miy possibly exist just as in violent
eartliquiikes ; but as their mignitude is very small, these lines
must generally escape our recognition, and it is habitually, though
erroneously, considered that the disturbance is uniform over a
circular seismic are:i.

When the intelligence of the outbreak in ]\lino, Owari, and
Echizen, wliich t(jok place on the morning of October '2Hth, lS9l,
was received in Tokyo, seismologists, architects, and other repre-
sentative scientific men were sent out to the shaken district from
several Government Departments. Particulars of the earthcjuake
soon began to reitch Tokyo, but nothing of any volcanic eruption
having anywhere taken ])lace.

A teleu'ram from Gifu announced a rumour that the centre
of the seismic disturbance must be in the neighbourhood of Neo-
dani. iîeport of remarkable physical changes in that quarter having
been recei^'ed, an official of the Meteorological Jîureau was sent
thither, and he reported that at Xogô a marked subsidence had
taken place, and that the gener:d n])pearance of Midori had under-
gone a complete transformation. On hearing this news, I started
for the scene of disaster to examine lines of fa all like those in Kuma-
molo, should there be any in the devastated region. I ascended the
Neo valley, which is said to contain the source of the great earthquake,
and found the conditi(jn of things very remarkable. The first thing
that attracted attention were many boulders that had been hurled
from the steep mountain sides, the number of which increased
at about Kimbai-a to such an extent that practically the sides
of the valley had slidden into the river, while the road had totally
f'-one in places. Ascending the v:dley higher, lnndslip>s v\'ere more

o9g TJ. KOl'ö: CAUSE OF THE GREAT

and more fre({neiitly seen. Indeed in tlie npper dale it may be
said that the greater part of the mountain slopes had slipped away,
carrying' with them tlie forest they were covered with.

Amongst the extraordinary things done l)y the earthcjuake, one
that always drew my attention was the earth-rent. It strikes
across hills and p:iddy-fields ahke, cutting up the soft earth into
enormous clols ;iiid raising them above the surface. It resenihles
the pallucai/ of a gigantic vide more than ütiijt]iing ehe (PI. XXXA .)
Indeed it is known by this appellation among the villagers. An old
Japanese superstition about earthquakes is that a monstrous cat-fish
lives underne-ith the Empire of Japan, and whenever this fish moves
there is an earthcjuake. The origin of this belief is not known, but
no doubt it has undergone several changes or modifications since it
was first originated. A representation of it was given as a drawing
in an almanac of the eleventh century. There it was de])icted
as the eartli quake- insect — a wonderful flat creature witli numerous
appendages and a head like a dragon, carrying on its back a map
of Japan. Tlie earth-yent which has cenj much tlie appearance of the
track of a mole, as just stated, stro)tghj reminded nie of tlie faticij of the
eartliqiiake-insect. It is prohahle that the belief of the earthquake-insect
as the aullior of subterranean convulsions maif hare arisen from the
outu-ard aspect of the fssure, produced hij a tectonic eartliguake as in
the case of the Neo xalleij.

The formation of crevices is the never-failing attendant pheno-
menon in violent earthquakes ; but the one in question is not of a
common sort, lîeing interested in this remarkable earth-rent I have
actuallv traced it for more than forty miles. It starts from about
the village of Katabira, not f;n- from Katsuyama, on the bank of the
Kiso-gawa on the Xakasendo, running north-westwards up to Fukui
in Echizen through the Neo valley (PI. XXIX.). Although the

EARTHQUAKE OF CENTRAL JAPAN, 1891. 399

geological stnicfiire of the region traversed by this great fault i.s not
so well known as that of Lago di Croco in tlie Eastern Alps, still I
tliink, as has been already pointed out, that I ani justified in
supposing the existence of a number of shifted lines of dislocation,
stretching from north-west to south-east across the North of Mino.
TJie event of Ocfohrr, 1891, seems to me to have Jieeu a reneived movement
upon one of tliese jrrexistinij tissiives — tlie Neo valJeij line of fault, hi/
which the entire region lijin(j to tlie riißit of it not onJij moved actiialJi/
downwards hut was also sliifteil horizontallij towards tlte nortli-west for
from one to two metres aJontj tlie jdane of dishmition. Tliis vertical
movement and hovizontaJ shiftinij se<nn to me to have heen the .^ole cause
of tlie late catastroplte.

330 B. KOTO: CAUSE or THE GKEAT

VI. The Course of the Line of Ihe Great Fault that
caused the Earthquake.

The Gfreat earthquake of Centra] Japan sliook the extraordinarily
Jarge superficies of 24o, 055 square kilometres, or more than tln-ee-fifths
of all Japan, and must be counted as one of the greatest physical
events of modern times. Let us see now how the fault looks which
produced such a tremendous effect ?

Faults or throws may be observed a.lmost everywhere in the
earth's crust, and geologists and miners are quite familiar with
their structure. But it rarely happens that a, fault comes into
relief in complicated mountainous districts. In less disturbed regions
such as the l^lateau of Colorado, or the eastern border of the Central
Asiatic plateau, the lines of displacement can be traced with great
certainty ; and the underground structure is usually reflected in a
great measure in the topography of the region concerned. In
the Alps and Central Europe, most of the earthquakes have hitherto
been ascribed to a tectonic movement of the solid crust through lineal
extension of the disturbed area, but no actual fault has anywhere
l:)een found which was formed at the time of an earthquake, and
could be reasonably assumed to be the originator of the disturbance.

The case of 1891 /.s quite otlienrise. Here ire could not onh/
positirehi ohserve the fault on tlie surface, hut also measure tlie height
anil length of it. At a place called Midori in the Xeo valley, the
flat bed of the valley was split longitudinally, and one side was
tipped off so that there is an abrupt step, measuring 5.5 to 6 metres
verticall}^ The earth very regularly took its angle of repose at the
break ; and the appearance, as we come to it eastwards from below,
is as if we were approaching a r:!ilway embankment (PL XXXn"^.).

EARTHQUAKE OF CENTRAL JAPAN, 1891,

ool

Where tlic vertical clisplucement is liot considerable, the line of the
fiiult a])]}ears on the surface like a rounded ridg-e of soft earth 80 to 60
cm. high and. as I liave already stated, re.'^emhles venj iiuicli tlw patli-
nriji of a (jitjantic mole (PI. XXXA".).

In tracing the course of the ,gi-eat fiult (indicated ])v the heavy
line, ri. XXIX.), I l)egin witli what I suppose to he the south end.*
In Xishi-katabira, a small village amidst hills of a grevisli Tertiary
sandstone, in the district of Kani, ]\Iino province, there is a place
locally called Kozé. Here, upon the slope of a s|)ur of hill, stood the old
monastery of Fidvudenji. The hill together with the entire buildin"-
slipped down int(i the paddy-field which in turn was broken into
clods of earth, and swelled u]) 5 metres high. FoUowino' the
direction of this remarkable landslip towards the north-west, the
paddy-field was seen sharply cut by a line, along which the nortli-eaM >tide '
lia I sh'fjIitJii i^iilixidi'l, mil hail moveorer lieeii !^]ufteil horizontaUij towanU
the )inrt]i-iresf for a di>itonce of 1 to 1.2 melre.^. That besides the

yertical move-
ment an actual
horizontal shift-
ing had taken
j)lace is proved by
the fact that the
originally straight
mound or ridsfe
called Azé which
•p separated neigh-
bouring fields, was

* Oa close examination in the fiekl, especiallj' at a))Out Kukuri, Ikeda, and Taka-
yama, I was not a])le to find any trace of the fault, which may ))e looked upon as the prolonga-
tion of the main lino of dislocation.

332

B. KOTO : CAUSE OF THE GREAT

now cut obliquely nnd shnrply by tlie line of fault. ^Moreover, the
continuity of the mound wns really broken and the mound with the
entire ground so shoved forwards that the detached ends coidd not
afterwards lie rejoined — (see. the accompanying wood-cut). It is
evidently quite different from what the miners call a ' heave ', — an
apparent horizontal displacement of strata by a mere vertical throw in
inclined beds, for in the present case the horizontal shifting can
be actually traced in perfect! 1/ ereti (jround.

Sketch map between Nishi-katabira ami ÜEjura in Mino province, sliowing the
fault (heavily dotted line). After S. Mori.

course oi

EARTHQUAKE OF CENTRAL JAPAN, 1891. 333

The ubove-meiitiotied line takes the direction of NNW.
At Tsuchidu, ground w;is depressed for u mile's length along
tlie embankment of tlie K-ani river, a small affluent of the
Kiso-gawa. Mount Daitenjin, lying to the soutli-west of Tsuchida,
on the s(3uth side of the Kis(j-ga\va, was sharply cut by the
line of dislocation, and the east side of this hornstone-slate mass
slipped a little downwards. The vertically dislodged line is visible
on the steep precipice of rugged hills, at the foot of which the Kiso-
gawa foams over its rocky bed. The line crosses the bed of the river
at the east end of Katsu-yama, on the Nakasendô, and completely
reduced the village to a heap of rubbish. We hnd here terraced
ground fov raising wheat and barley on the hill slope, and a piece of
this ground about 2.000 square metres (2 clw). lying within the
precincts of the Ijuddhist monastery of Ktdviizenji, w^as so thoroughly
turned over ^ivoxn the very bottom that all the original marks were
entirely effaced from the dry field (liata), and there remained but
clods of eirth and upturned roots. xllthousfh nothing of the under-
ground solid crust was to be seen on the surface, still it is almost
certain that the (jrigin of the disturbance did not lie within the
superficial covering of the soil, but must be sought for in the deeper
portion of the crust. It appears as if the loose soil had been jerked
off from the hard under-ground by an intense shock from below.

The main line of disturljance now points N. 10° W.; it then
goes through s[)urs of hills and paddy-fields, causing damage to
the villages, Osugi, llazama, and Nishi-tabara. After making a
sinuous curve it crosses the Tsubo-ü'tiwa. passes throuoh the ^■illaf'•es
of Kuraclii and (Jvana, crosses the Naofara-^'awa at Shiino-shira-
gané, and then taking a north-westerly direction, goes through Sen-
biki and Toda, passes over the Mugi-gawa, and proceeds ttjwards
Mori and Sebo, till it reiches Ishiwara. In the last-mentioned

334 B' KOTO: CAUSE OF THE GREAT

village there i.s an artiticially coiiJitracted pond of considerable size,
for irrio-atin"* neiirhbourinu' ijaddv- fields. It was fed bv a small
stream from the north with its outlet on the south, Ijut the line of
fault f'-oin"- rid-ht throuu'h the middle of it in the east-west direction,
its northern half together with the neiglibomàng fields of 17,851
square metres (1 clid <S tan) subsided, and was also shoved
a little to the north-west. The result of this vertical as well as
horizontal movement of the north side ^vas that the outward
passage at the south end of the pond lies now on the higher level.
The quantity of water remains nearly the same as before, and the
deserted ].>ond is still fed from the entry passage on the north, so
that it is pr(jbable that the water s(jaks away through the new
fissure as fist as the small current enters the pond through the
channel.

The line now runs, through Taromaru. a few steps southwards
alonf»" the newly macadamized road that connects Seki and Takatomi.
One could easily recognize the fault as such by a slight difference in
the level of a perfectly even field, the north side being a little
the lower. About five hundred steps east of Takatomi, it crosses
the road (jbliquely at Mori, and the north side became again the
lower by 1 .5 metres and at the same time was horizontally shoved
about 1 metre westwards. Takatomi is a tolerably large village, with
a population of 1,7-lG, lying north of Gifu, and I saw in no other place
within the devastated region such a complete destruction of buildings
as occurred here. All Avas shattered and levelled with the gromid.
About 87 persons were killed and 158 wounded. At the north end
of the village the fault appears in d(3uble lines (see the accompanying
sketch map), along which the ground had been shifted horizontally, and
also become continuously lower towards the north, so that a once
even paddy-field now f )rms a good natural slope.

EARTHQUAKE OP CEXTEAL JAPAN, 1891.

ri8i

Sc file 1: 25,000

Sketch map of the environs of Takatomi, shouino- the course of fault (heavily dotted
lines). The stippled portion on the right is the depressed side of the fault being the newly
created swamp of F ukase ; ab, the new channel specially constructed for drawing off the waters
of the swamp. (1) and (2) the two other depressions formed at the tim(> of the earthquake,
now filled with water: od, being the channel for the pool (1).

Tlie smnll 'Itibn-a-awü. n>'inu- high in the innihcni inonntaiDS,
flous (lowii Iiy Takntoini lownrds (lif'n. ti^ join the .Vno-ar:i-2'nwa.
Jiy the great earrh<.|iiake a tract of Jand and the riser bed, lying to the
north of Takatomi, were considerably lowered, m that the contentiï of

,336 li' K"OTÖ: PAUSE OF THE GREAT

the Tobu-o-;iwa lost tlieir outlet, and tlie viIlao;es of Nislii- and Miofashi-
Fukase, comprising an area of 2 square kilometres, or nearly 220
chO, were transformed into a deep swamp in consequence (compare
the annexed sketch map). When I was tliere last autumn, the
farmers were oblig-ed to cut the g-niin in boats, October beino-
the month of the rice liarvest. It was very remarkable to
see that a o-roup of farmers' cottag^es, standino- at the northern border
of the newly created swamp, had miraculously escaped the collapse,
though scarcely 2 kilometres north of Takatomi, a phenomenon
due perhaps to the foct that tlie place is just 1)ehind a low hill
which seems to have absorbed the wave motion of the earth-
quake on its way. The earthquake-shadow so created, finds analogy
ill the action of a strongly blowing wind, cut short by a liill in its
path, leaving the other side in the wind-shadow. It is almost beyond
doubt now that the destructi\e motion of an earthquake depends
like that c^f the wind, more upon the topography of the shaken district
than upon the angle of emergence of waves froin an assumed origin
within the earth's crust. I rould easily multiply such examples of
the eirthquake-shadow l)etween 'J'akatomi and Omori along the great
fault. Houses between or near side-valleys generally escaped the
destruction, wliile those on the plain through which the line passes,
could not withstand the shock and were thrown down.

The great fault-line crosses Toba, where the houses were crushed
to rubbish, and proceeds directly westwards to Horachi. In the latter
])lace again the north side sulisided and became part of the new
swamp, already referred to. The line enters a hill at J\[ochi-nari, cuts
through a spur of hill at Azuki-zaka, and then i<)llows the northern
foot of the hills westwards. It appeared for some time after on
the surface through the whole region, exactly like the track of an
enormous mole.

earI'hQUâke of CeN'tkal Japan, "1891.

337

It goes right through tlie hamlet of Jôbara (Uuiéhara),* where, in
a front garden adjoining a farmer's house, there are two stately
persimmon trees, Diospi/ros hdi, which liad stood time out of
mind in an en;-t-west line. The line of fault traverses the space
between the two from the south-east to north-west, and as usual
the north side was shoved north-west, so that, to the great
astonishment of the owner, they now stand in a north-S(^uth
line instead of east-west, without being in the least impaired,
and still adorn a corner <jf the inclosure. The plane of dislocation,

which served at the same time as
that of sliifting, appeared on the
hard face of the ground as a mere
line, so that to any person not
initiated into the structure of a
fault the displacement of the trees
was cjuite unintelligible, and ap-
] eared io the astonished peasants
as a marvel with no apTxu'ent cause.
./ A lew doors be3'oiid, there was a
water course in front of a
cottage, as is common in Japanese
villages, which being cut by the
line of fault, and the ground on which the house stood, sinking shghtly,
unexpectedly inundated the place. After this, the line appears in the
muddy fields of Nakamura and Köden,.with the north side dislodged.
In consequence, a second swamp resulted wliich lias an extent of 25
hectares, or nearly 25 clw. From here to Omori the road ascends
the slight elevation of Koshigirizaka, at the very top of which the
fault cuts off the solid rock, leaving the north side depressed.

* See the sketch uuip, p. 332.

338

B. KOTO : CAUSE OP THE GREAT

The villages of Öinori, Ogura, Fujikura, Horada, and Matsuo are
all clustered in a basin-.shaped widening of the Ijira valley, which in
conformation with the general system of valleys in the north of Mino,
runs in a south-easterly direction across the strike of the Pahvozoic foi--
inations. As it is situated in an old river l)ed, Omori suffered the
most by the earthquake, many portions of the soil being niised or sunk,
and innumerable fissures traversing the village in all directions :
so that it is somewhat difficult to follow the main fault in such a chaos.
The wliole system of drainage was deranged. The line of dis])lacement
next crosses the bad of the Ijira-gawa, cuts obli(iuely through the
boundary of Horada and Matsuo, passes over the top of a hill, called
the Nishiuuuié pass, at the border of the three districts of Yamagata,
Katagata and Motosu, and then descends to Kawa-uchi (Toyama),
with always its north side depressed, and as observed by me driven
northwards for alwut 2 metres. T'he rent then points north-north-
west, runs along the eastern slope of the hill in Toyama, appears on
the steep descent of Kane-zaka on the way t(3 Kiml^ara, proceeds
thence directly northwards along the western declivity of the hill, and
enters the Xeo vtdley for the first time at Kimbara from the Ijira
valley lying east of it.

When it had become current that the source of the earthquake
had been in the iN'eo-dani, many people ascended that valley in order
to satisfy their curiosity to see the site from which reputedly the
severe shocks had originated. They usually took the road from Gifu
through Yamaguchi at the entrance of the valley, along the Xeo
river to its source, and in so doing, were somewhat disappointed while
ascendins: its lower course. Less destruction was visible than was
anticipated, an impression produced by seeing some houses still
standing, after having passed along the road in the Mino-Owari plain
lined with ruined houses on both sides, and many visitors ])Ositively

EARTHQUAKE OF CENTRAL JAPAN, 1891. ;53C)

as^serted that the earth^^uake could not have originated in this vallev.
Had they come to Kimbara, where I left off the description of the
earth-rent, this notion would soon liave vanished.

Kimbara itself hes on the left of the fissure, but so near to it
that all the buildings in the village entirely collapsed. Ar the north
end of it the road descends the steep slope of Dando-zaka. and brinu's
us to the beginning of the phice of greatest destruction in the vallev.
Beyond the steep descent there was no trace of road left bv (he
earthquake ; rubbish and blocks of hornstone had oljstructed and
buried it under them. For a few days after the grejit shock there
was still everv now and then, the crash of some mass of rocks falling
from precipices on either side of the valley that had l)een left by a
landslip.

The rent now runs east of Hinata, where the river bed makes
crooked turns, and at Hirano, the next village, passes on the right,
and at the south of ]\Iidori, it appears on the left side of the Xeo-gawa.
and here one of the most wonderful effects of the earth* piake
was to be seen. A fine new road (see PI. XXXI \'.) leading to (üfu
had been obliipiely cut into two, and the lower end with the
surrounding fields had sunk about 6 metres below the upper end.
The road is here on the west side of the river, and the eastern
half of the valley, which includes the Xeo-gawa and opposite hills,
shows the tilting edge, or cutting of the fault. That tlie east JudfJuul
been puslied é metres northwards, in C(jnformity with the general rule, is
well seen in the photograph by an abrupt change in the direction of
the displaced road. So far as I am aware, the formation of such
a colossal fault on the surface, as this in Midori, is exception-
ally rare, and finds its equal only in the ' Ullah-bund,' or God's
dam at the Runn of Cutch, in the lower course of the Indus.

Those who have followed me with patience to this point in my

;540 ' " ^B. KOTO CAUSE OF THE GEEAT

descripti(jn of the earth's rent from the village of Katabira, will
have seen that I ha\'e always spoken of subside net' of the n'ulit siele.
accompanied bv horizontal shiftiihj totvanls the nortli or nortli-irest,
and now lijoking at the fault at Midori, may object to my con-
tention that the great throw is a prolongation of the main faidt,
that the ircsl liait' had here sunk instead of the east. It seems, however,
that Ave have here an abnormal case, and that the east Jialj] ineliid-
intj tJie river became raised. What a-oidd seem to faroar tJiis rieir is
t]u(t a Utile hifflier up the river irlial was hniuerhj a slailloir rapid stream
:27 metres across and easilij j'ordahle, broadened out into a small lale,
63 metres in a-idth, of still iraler irliicli a hoats}iian's pole cannot j'atJiom.
A dam was formed below and the current now ünds its way in a
narrow diverted stream under the opposite hills. In explanation
of this special case. I would soy that, in the enormous convulsion
caused in the valley between the two chains of hills, the weight of
the hills on either side caused a cracking îind uphea^al on the east
side of the valley, in the same way that a severe shaking given to a
heavy abutment of an arch may force up its cr<jwn or centre.

At the north end of Midori, the road crossed the valley to Itasho,
where there was formerly a bridge ; but it is now necessary to cross
in a ferry boat, the valley having been transformed into the
lake, already referred to. At Itasho. again the fissure appears
beinsr like a mole's track when seen bv me. both sides being nearlv
on the same level, though the east half had been shoved northwards
as shown bv the horizontal displacement of a broken ditch in the rice
fields. It passes through Ichiba, and Ködokoro, reappears on the
road at Xaka, and o^oes throu"-h the middle of the fields at Osso,
with its usual characteristics.

The villa"-es of Kadowaki and Nao'amin»'' lie out of the exact line
of reut, and the damage sutlered by them were therefore comj>arati\e-

EARTHQUAKE OF CENTRAL JAPAN'. 1891, 34|-

ly speaking not very he:Tvy. Sfill it is not to bs supposed that
their liouses were entirely spared, the whole surrounding soil at the
time of the great earthquake heaving in a state of vibration and doino-
mucli mischief. There was terrible destruction on the line, as in
Tenjin-dö, a few hundred steps beyond N"agaminé. The next village
is N^agashima where the rent was to be seen on the road side. The
ground wns bodily shifted with the houses 2 metres forward, and subsid-
ed 1 metre on the riglit side. Turning off from the main course of the
Xeo, and passing over l^y a bridge to Xogo. we find the rent striking
acn-oss the mountain stream, depressing the eastern ])ortion of the bed,
and thus converting a torrent into a slow stream.

Ivunning northwards, it enters the hill .at the l)adv of the
temple of (Tongen, having caused landslips all along its path. This
temple was founded in 717 in honour of the Tlongen of Haku-san, a
'lapanese deity in a ]^>uddhisr fn'in, and though small in scale
was of ancient date, having been erected in 1673 on the southern slope
of the hill, overlookino- the Xeo-o-nwa,. This wooden buildinçf of rare
anti(|uity f)r elapan was hurled io the ground in ruins, attesting
how long a period had elapsed sinœ a, shock of similar violence had
visited that quarter. Yet if we were asked whether the twin
provinces of ^lino and Owari were a place where earthquakes had
not been fre(|uent we should reply in the negative. In Japan there
are some seven hundred stations where earthquakes are observed,
and from several of them situated in the Mino-Owari ]ilain, we find
that in the six years from 1885 to 1.S90 the number of shocks
recorded in that district have been respectively 9, 4, 10, 1'2, 15, and
36.* Still going backwards in the annals of earthquakes, we find
again that violent disturbances took ]jlace in the district in 715,
762, 1596, 1707, 1723, 1819, and 1854. Many dwellings, store-

*- Milno-Burton, Tlie Great E'trthqnnlie of Jnpmi, 1891. p. 6.

a42

a. KOTO : CAVSE OF THE QEEAT

houses, and ;even mountains suffered, people and animals were
killed, rivers were stopped up, and floods were occasioned. J3ut in
spite of these subterranean convulsions, the temple in Xogô, erected
in 1673, had stood well-preserved down to the present generation.

From the facts already given, it seems not improbable that the
centres of disturbance of former times have not been located in
the Xeo vallev. In pre-historic times, however, tliere must have
occurred several gretit earthquakes, as is evinced liy the geologi(.'jil
structure of its mountains. In the great earthquake of 1854. which is
still within rlic memory of many, the Xeo valley had been Ijut very
little disturbed, we were told liy old folks in Xagaminé. whose houses
had coll;ipse<l completely in the last catastrophe, and tliat many of them
built more than a r-entury ago. had remained till tluit event in tolerably
good. condition, and with(jut being impaired ly any former earthquake.
The rent appenrs again at the bottom of the Konokana-(]ani,
a side- val IcA' whidi we fallowed up from Xogö, here diverting the

main course of the
Xeo-gawa. It might
lie traced with great
exactitude as far north
as the entrance of the
sunken gully of Fuji-
tani, wliere the line ol'
displacement of the
rocks appeared on the
surface like a rounded
ridge of soft earth 1
to 1-^ metres high, as

seen in Plate XXXV.
The ii^round had been

ÉARTH(jUAKE OF CEXTüAL JAPAN, 1Ö91. ;5i;;

depressed on the riuiit yide. and .sliifled liorizuntalJy in tliu usual man-
ner, a« wi]I he clearly understood from the annexed wood-cut. Lastly,
we arrived at the place called Fujitani. which i.s now tolerubly w-ell
known tlirouuh the su.gg'estion of Mr. Jguchi, tliat it was the seat of
the source of the earthtpiake. It is a branch AalJey of tlie Ivonokana-
dani. circumscribed l)y liills, except on the stjuth. i\t the centre of it,
we were told, a hole 1 to 2 metres in diameter had existed, into wl\icli
large stones and boulders being thrown were heard for some time
striking and e('hoing in their descent to an (?) unfathomable de[)t h .
Time had cl<jsed, it was ;aicl. the opeuing. and there remained but
u shallow depression in its j>kice. The ground indeed had Ijeen
intensely convulsed, and the face of nature entirely changed. The
sides of the hills Avliich iianked the valley had slipped down, and the
forest upon them still presented a singular scene of confusion ; trees
standinu' inclined in every direction, manv with their trunks and
branches broken. The course of a small stream was stopped and a
new lake were created there. A\dien these marvellouslv U'reat changes
occurred, the shakinir nuist base been terrific — inconcei\able — vet I
cannot believe that the slight depression in Fujilani to have been the
origin of an earth([uake wliich had shaken a great })art of 'lapan.
The sunken gully of Fujira.ni, alread}' alluded to, is only a prolonga-
tion of the rent which we followed u]) there for about o'2 kih^metres.

The fissure cuts c,if the rear of the de?)ression of Fujitau i, and
comes in siirlit aii'ain Ijevond the hill of iJTevwacke sandstone and
clavslate. at the bottom of the main course of the Konokana \ alley,
which tei'inijiates at the foot of Front llaku-san. llie valley hereis
naî'row and forms a deep gulch, bounded by oxerhaJiging ]ti'cci])i<'es
on the east and west. l'>y the earthquake, the smfices <jf hills (;n
either side slipped down the valley, and left them almost bare of the
fine tindjcr which had clothed them. The fresh verdure of the steep

34-4 ^'- ï^^'i'O ■■ CAUSE OF THE GKEAT

mountain-side had given jthice to a rocky de.sert. and even, a.s we
passed down, avalanches of rock^<, accom]>anied by a noise Uke that of
an immense torrent or cascade and Ijy a \ibrati(;n of the ground,
occasionally occurred. 'Jlie shocks had been far more destructive
there than in Fujitani. If any one had been as the villtigers were, in
a position to look on at a distance at this colossal sliding of hills, he
would have seen columns of dust rising up, and heard tremendous
sounds, and might have tîdcen these phenomena as those of a
volcanic eruption, for the efl^ects of landslips and \olcanic exphjsions
closelv resemble each other. The configuration of the valley Avas
entirelv changed ; the course of a small stream, running on its west
side, was transferred to its east side, and at ] »laces n()W takes an
Underground course, reappearing farther on. Unfsmilinr obstacles
made themselves apparent, and small hills covered with forest had
come into siodit which had not been seen before.

At about 10 kilometres from JSTogö, the earth-rent goes over to
the left and cuts the top of a ridge, c:dled Shijügara-dake, right
through its middle. We passed a stormy cold night in the open air on
this summit. The line of f suit then enters Shiratani, a Irranch of the
Tokuno-yama valley which, as I have already said, ruris ]^arallel to,
and lies to the west of the jS'eo valley. The gulch of »Sliiratani was
severely torn and rent. It appears shattered and half-naked, and no
longer affords a fine green pros|)ect, as before, but is stripped of its
woods and na.tural verdure. The fissure advances still further north-
ward, touching the ea;-;tern shoulder of Haku-sa.n.

80 i\iv we had traced the great earth-rent up to the north bound-
ary of Mino, beyond Avhich is the province of Echizen. It wa>s the
Ititli of ]S^ovend)er, the nineteenth day after the earthquake, when I
bes^an the ascent of llaku-san, in comranv with Mr. Wakimidzu. a
student of i>eoloL;-v. lîut it wa.< too late in the season to no (_)n. 1 he

EARTHQUAKE OF CEXTllAL JAPAN, 1891. ;>45

weatlier was cold, and some of the higli points were already white with
snow ; nionntain-passe.s liad become impassable, the road h;id totally
gone in places, or left nothing but n difticiilt foot path. Such being the
state (^f things, I had to abandon the idea of reaching the t<^wn of
Fukui by the pass of PIail)öshi, and returned direct to Gifu, for many
additional days would have been necessary to get to Nukumi, Kumagö,
and ^linomita, all in Echizen, where exteiioive Lmdslips were said to
have taken place.

Although I could not examine pers(^n;dly the devastated reo-ion
in the south-east of Echizen, at the boundary of Mino, still I am
fortunate enough to h-ive received several reports from village-masters
and the police authorities of Xukumi, and, last but not least, from
j\Ir. Hiki, another student of geology in the Uni\'ersity. From
their l)rief a.ccounts it seems highly probable that the rent proceeds
from the summit of Haku-san to tlie poor hamlet of Xukumi in
the district of Ono, where eleven out of thirteen hou.es wei'e
completely shattered and the remaining two narrowly escaped
collapse. It is stated in one of the reports tha.t there is
a "fissure running from south-east to north-west, just as i.; the case
in Mino, and that one side of Üie fissure has been l)odiIv shifted
horizont:d]y for about o metres. It passes by Ivumago,* along a
rivulet, and then crosses the pass of Minomata down to the village of
the same name on the western foot of the rido-e. The line seems to
continue through the villages of Anzenji, and Mizumi to Taniguchi, and
eventually reaches Hirose, after traversing the Ijed of the Asuwa-gawa
wliich flows at its lower course by the city of Fukui. Throughout the
valley of Minomata, dotted with the above mentioned hamlets, ex-
tensive landslips are said to have occurred, c;uisinii" dama^'e to both
life and propert}^ To the westwards wdthin the Tertiary terrain, I

* It is erroneously spelled as Ktunai/itwn in the map, PI. XXIX.

346 ^- Ï^OTO: CAUSE OF THE GREAT

nm not (|uite sure of the presence of any fissure n,s tlie prolonLi-ntion of the
great funlt-line. still [ liüve strong- reason to l)elieve tliat tliere were faint
indications oi'sucli a rent in tlie lineal extension of the (listnr])ed area,
which be,^-inning at Hirose, extends over Xi si li-küchi, Ainoki (l)etween
these two villages is the slight elevation of Xakaban-saka, much dis-
turbed by fissures), Ochiai, Kawasliima, Matsunari. and then makes an
abrupt cliaiige in a northerly direction towards Minanii-i, and crosses
the pass of Yenoki-zaka to Kökita as far as the city of Fukiii. in Kclii/en.
It will be seen from the map (PI. XXL\). that the neigh])om-ho()d
of liikonc at the eastern bcmler of Lake lîiwn, was severelv shaken
and deeply damaged by the earth(juake. whereas the stretch of land
between tliis .Tnd the ]\[in()-Owari ])lain suffered verv little. Such an
abnormal nlienomenon hîid been already noticed bv KliH>-e, l(~)no- a"'o
as 1861, when he says : '• dass ein Erdl)C'ben diu'ch seine letzen, abge-
schwächten AVellen an einem anderen, weit entfernten Funkte eine
selbständige Erschütterung her\'orrufen kann, die möglicherweise einen
gana anderen Ursprung hat, a>ls dieses ])rimäre Erdbeben. Es ist dies
eine Erscheinung, welcher bis jetzt noch niclit die Ijeachtung gewidmet
woi'den ist, welche sie verdient. Es giebt nämlich Stossgebiete, welche
gewissermaassen den Wiederhall oder das Echo weit entfernter Erd-
beben bilden, in denen zwa.r die Disposition zu einer Erderschutterung
vorha.nden ist, diesell)e aber häufig erst, Avie es scheint, duix-h eine
andere geweckt werden muss."* A. \. T/isaulx** named such a.n earth-
quake the sympathetic, or Jlclaisiu'lirn. The destructive shocks near
Hikone, esneciadlv Xa^'ahama. p,t tlie time of the «Treat convulsion
in tlie neighbouring provinces, seem to me to have been caused by
the above-mentioned secondary earth(|uakes or Rclai^Jx'Jx'u. Tt must,
however, be remarked that the intc^nsity of shocks felt on tlie surface has
greatly to do with the oroiimpliic condition (^f the region concerned.
besides the reason given l)y v. Lasaulx.

* lieber die I'maclicu der in d<'n Jahren 1H5Ü hix IHÔ? attittiiefundeucn Erdernclmtteruiiiicn.
"** Ki'Untcntr'K Hdiiihrörtei'hmli ilrr Miiierahiq!', o\v.

EARTfTQUAIvE OF T'EXTTfAL JAPAN, 1891. ;]4'

VII. Concluding Remarks. ,

S[U':!kiriu- u-orier:il!_v, it mav 1)0 süid th-it all lar^'O (':n'tli(|iiakos are
a''C()iiij)a]iu'(l liy tlie formation of fissure.-*. Tlic oracks, fissures, and
slips formed at the time of enrMujuakes are oi" rnr/nns ii<itiir('s. and of
diffère til d'liiens/iiiis. Some oc(mr aloiii;- a road, oi' run near the up])ei'
edge of a ehlf. 'I'lie re-ison that ('ra<'ks slioidd lia\e oc(au"red in sudi
a position as tlie lattei- rather tl\an in otliers is prol)ahlv owinsj,' to tlie
greater motion at sueli a ])Ia.('e. (hie to the fu-e of the cliff l)cing un-
supported and with nothing opposed to its outward motion. Similar
i-emarks may he ap])lied to the l)anks of rivers and to ;dl dej>ressions,
whether natural or artificial, which ha\e a steee]> slope. At sueh ])laces
tlie waNCs of the shocking emerge on a free surface, tending to project
the su[)erfici:d parts away from those hehiîid, and thus i'orm a fissure
])arallel to the free surface.

]\[oreo\er. slips and fissures depend upon the slnielnre of ror/.'.s-,
and occur on a, ]^;u'ticularly grand sc:ile where the strata dip into
iW against the slope of the walls of a valley. V\\' ha\(' numerous
examples of this in all the side-valleys of the Xeo river, whicli run
parallel to the strike of a com])lex of clay-slates, sandstones, and horn-
sione-slates, thc^ main course of the river, as alreadv stated, heing
directed against the strike of the Paheozoic formations. This often
nfisled observers to see in the side-valleys the seat of the origin of
the earth(piake, hecau.e tlie sliocks were far more destructive iIum-c
than in other places. Hoirerer (jreal tlie deMrvcliou inis^ if uns HOlliimi
more ihmi the superßcial ep"ec(s of f]ie eaillniiiafe^ Imi iml the cause of ii.
There are other fissures, slips, and cracks of great geological im})ort-
ance, and of quite different origin, which should by no means be
confounded with tliose already mentioned ; as has unfortunately been

o 13 B. KOTO: CAUSE OF THE (iTîEAT

often (lone. Thov inv renlly connected with underuTound structure and
are due io displacement of tlie rock-masses whieli constitute the
external ciaist of the earth. They therelore (vcur where there exists
a discontinuity of rocks, and the earth-rent which we have descrihed,
and which is the mtiin ])oint in the present pa])er, must l)e regarded
as an exam]>Ie.

Tills rail (il iJw surface ioi»]; mull ij'drioiis forms. When traversing
a ridge of mountain^ or a spur of hills, it caused extensive landslips,
one side of it descending considerahly in level, carrying the forest
with it, l)ut with the trees com}>licated1y interhx-ked or prostrate on
the ground, as on the ridge of Ilaku-san. On flat ground it
sometimes created a terrace of »about G metres in height, as in Midoi-i
(PI. XXXn .), somewhat like a railway embankment seen from afar.
When the vertical displacement was not very consider:d)le, the earth-
rent left a mark on the gi-ound, rcsrmhlimj rciij much ihr patluraij of a
(liijiitttic molr or the trade of a ploinili-sliarc (PI. XXXY.).

The manner in whi<-h this peculiar low mound was formed may
be ex])lained l\y reference to a monoclin:d flexure — a geological struc-
ture Avell exhibited on a grand scale in the L'lateau of Wahsatch.'* 8u]>
pose the iiat l)ott(^m of a vaHey like the Xeo, filled up with soil and
gravel which rest unc<3nfoi'mably upon tlie hard mass of the older
rocks, and form their -cover,' and tliat the basement should give way
by faulting along the ATrtical thrust-plane ; there a certain ])ortion
of the uncompressed 'cover' will tliere1)y be uplifted, so as to
form a rounded ridge of earth by the lateral compression of a sub-
jacent mass along the line of discontinuity. In this w^ay a mono-
clinal flexure in the loose superficial covering, which aj^pears in section
as a flexure connectinii- two horizontal b;n-s of strata, would be

* C. E. Button, liqmrt on the Genlnrj]i of tlw Hifih Plotefiiist of Utah, p. 25-51-.

KAKTllgUAKE OF CENTKAL JAPAN, 1891.

:34<)

produced by direct lateral pressure exerted at the ends of the bar;?.*
Besides the vertical inoveni-jnt. horizontal shiftiijo- of either side would

take I'lace along" the same
-ü^^^Xl plane of f uilt, and the raised

;]i;^-i^ ridg-e AV(3uld Ije much dis-
■ '":^-.yC'^'i_5-^^^~Z turbed and become a con-
fused mass of clods of earth,
^D?o'llQoâ?ïo^?,'i^°'^°0'^'" <>^ sh(jwn in the subioined

^;'^'4,nXi:E:^^f,l^ w.)od-cut. The flexure in
V/^ //// / // this case had better be called

the niONOcIinic diaijonal
// Tl'-'.ciiir. The peculiar scjft

mound of earth, of which we
have often sp<jken. behjiigs t(j such a flexure.

This unique track, though at first sight it seemed quite insigni-
ficant and was C(,)nse(piently usually overlooked by casual observers.
is of gTe;it geological bearing. Unlike other p.ccidental fissures it is
characterized ])y C(^n.<iancy of direction and regulai'itv of course.
Starting from Kataljira near the Kiso-gawa, it runs up its length
through the Xeo valk'y to Ilaku-san (a distance of 64 kilometres),
and then seems to proceed north-west up to the city <)f kukui. for the
extraordinary distan('e of 11 L^ kilometres, or l^S /•/. The one with
which we are nujst concerned, is the line of fault oi- displacement of
rock-complexes, along which, as I h:i\e repeatedly pointed out, the
ground on the Irj'l side lunl suhsiilrJ j'r.jiii | io G uuircx^ and ai iliv same
time been ]iori:onlalli/ s]iij'ied for 1| io :i iiwiirs in a nortli-icesierh/
direction. The only exce[)lioii to the general rule was the fault in
Midori, where the land w^as hjwer on the west than on the east j the
manner in which this special condition may be supposed to have been

See The cause of Monuclina! Flexure, by A. J. Jnkes-Browu, Geol. Mag. 1891, p. 505.

3,-)(j B. KUTÖ: CAUöE OL' THE (.iKE.VT

broufflit about, ha« been already stated, uaiJieJv, that it was the enr4
half, which was eh'cated through some local circiiiiistances and not the
west side depressed.

In reu'ard t(3 alterations of relative level, none (jf niv observations,
however, establish which side it was tluit moxed, or whether Ijoth
moved Ijut in a different manner. It mast always be remembered
that to ascertain a change of level is a sul)ject of c(jnsiderable dif-
iicülty almost incapable of determination, exce[)t where the sea-coast
happens to have partici])ated in the principal mo\ement. In the last
earthquake we had no opportunity of observing such phenomena, on
the sea-coast, either of the Pacific Ocean or of the 'lapan Sea ; prcjbably
because of the line of the principal fissure being entirely confined to
the interior. Had it been possible to obsei'\e the fissure on the shore,
it might even then ha\e been impossible to determine whether an
elevation or a depression, even of several metres, had occurred, because
there would be usually nothing at that point to mark the mean
sea-level.

As data on which I could rely, in ascertaining the actual instead
of the relative change of le\el of the ground, were not at my disposal,
it seems to me very natural to su]>[)Ose that it was suljsidence rather
than u})hea\al which took place along the line of the shift ; and it is
the eastern wing which stands usually at the lower level. Jjut it is
another problem to be solved how far this de])ression extends easter-
ly ; whether the whole of Eastern Japan pa.rticipated in the down-
ward movement, as in the '"sunk country" of JSew ^ladrid." created
at the time of the great eai-tli(|uak(' of lNll-12. or the "sag"
(Inihrii of the J.ake of r>aik;d, at the mouili of the Senega ri\ei
or whether the movement was limited to only a few kilometres to

* Lyell, Vrinriplux of (leoloni/, 12th edition. Vol. II, p. 108.

** Perry, Xotf on (he Eaithqual^c oi' 1SG2, cited liy Öuess, in liis Das AntliU der Erde
lid. 1, i-. Jl.

or

EARTHQUAKE OF CENTRAL JAPAN, 1801. 55]^

the east. So far as my local knowledge extends, there seems to exist
only one regular line of shift in the convulsed district, from which
Ave may fairly conclude that the subsidence attending it, is not of
the kind called '' sag; " and I do not believe that the half of Japan
sunk down, but that only the land near the line of fiult became
sliglitly depressed.

Of every large earthquake, we find the accounts full of the
mutations which the earth underwent through the Jigency of subtei--
ranean movements ; tor instance, the formation of cracks and fissures,
besides permanent upheavals and depressions, accompanied usually
by spirting up of the squeezed groundwater and sliding of detached
portions of the mountain-sides. Of movements like these, that of the
IJllah Bund, in the delta of the Indus, is the most remarkable.
The real occurrence of the much talked of rhapsodic movements alx^ng
the western shore of South America, is not entirely free from doubt.
Immediately after the convulsion of 1819, the inhabitants of Sindree,
in the llunn of Cutch, saw at a distance a long elevated mound, where
previously there had been a low and [perfectly level plain. To tliis
terraced tract they gave the name of ' Ullah Ihind,' or the ' Mound of
God,' t(j distiniiuisli it from several artificial dams ])reviouslv thrown

7 0 1 ./

across the eastern arm of the Indus.*

This ' Ullah Bund ' seems from its description to have a close
resemblance in its outward aspect, to the fault at Midori, in the JSTeo
valley. As to the manner in which the ' Mound of God ' wa.s
formed, the views of geologists are divided. Lyell saw in this newly
created dam a true upheaving of the ground, while Suess considers it
in another point of view. Suess** says, ^^ Es handelt sich hier vcder mit
Er! I eh un (J con Eand, noclt. trie ich selbst einmal^ irre(jej'il]u-t durcli andere

* Lyell, loc. cit. p. 100.
** Dag Antlitz der Erde, Bd. 1, p. 02, aud Entstchiniij der Alpen, p. 152.

352

B. KOTO : CAUSE OF THE GKEAT

Darstellungen, vermutliet hahe, urn Faltenhiklung an der Oherßäclte, sondern
nur um das Hervordringen von Grundwasser und des Ncwlisitzen eines
scharf abgegrenzten Theiles des scldammigen Bodens.'^ Sues.s explain« in
similar manner tlie formation of the ' suidv countrg ' of New Madrid, the
depreä.sion of Baikal Lake, and those subsidence« at the mouths of the
Ganges and the Ijrahnr.iputra, at the time of violent earthquakes.
Tliey vere not, according to him, connected villi deep-seated movements
altering the relative level of sea and land.

The great fault of Xeo, by which I mean that long line of earth-
rent which traverses a distance of 112 kilometres from the Kiso-
gawa to the city of Fukui, cutting the hills, mountains, and plains
alike with remarkable regularity and sharpness, is clearly not like that
of the Ullah Bund, caused by the mere settling of superficial Alluvial
soil.

The sudden elevations, depressions, or lateral shiftings of large
tracts of country which take place at the time of destructi^'e earth-
quakes are usuallij considered as the effects rather than the cause of subter-
ranean commotions ; hut in mg opinion, it can he confidenthj asserted that
the sudden formation of tiie ''great fault of Xeo' iras tlie actual cause of
tlie great earthqiud^e of tJie '^titlt of Octoher, 1891, u-lticli sliool- an area
comprising 213,055 S'piare kilometres, or more than 60"/,, of tlie tvliole extent
of the Empire of Japan ; that is to say, an area equal to those of the
British Isles, Holland, and Denmark put together.

It is an established tenet of li-eolonfv that a sudden f udtin^- of the
eu'th's crust will cause a shaking which is designated by the general
term of tectonic eartliquale. The faults resulting from tangential
movements are of two classes, those running parallel to the strike of
rock-complexes, across the axis of mountain-ranges. All kinds of
tectonic earthquake are usually considered destructive and extensive,
as compared with those caused by a depression or by a volcanic

EARTHQUAKE OF CENTRAL JAPAN, 1891, 353

explosion; and of all llie tectonic eartlujiiake« a snddon faultinî^ of tlie
solid crust across the strike of strata are said to ])rodnce tlie most
fearful kind of eartli-niovements, as is evinced l)y tlie Spanish earth-
([iiake of 1(S,S4, along the transverse fractures of ^lalaga. ]\[otri], and
Gnadix across tlie lîetic chain of Andalusia* (Suess' HJattcrlicJn'u),
One of the characteristics of the transverse faulting is tlie simultaneous
occurrence of the horizontal ' carriage ' of a thick mass along the
vertical thrust-})l:ine, which is very rarely ohserved, if ever, in longi-
tudinal fissures.

The hackbone of South Japan — the cordilleras of the Sinical
system, traverses the boundary of the two provinces of ]\Iino and
Echizen, in the east-west direction, with the prevailing dips of the
Pala?ozoic formations towards the north, as is shown in V\. XXV III.
A system of p'u-allel, transverse valleys intersects the axis (^f the
mountains in an oblique direction from north-west to south-east, and
the Xeo vullev, id(Hiir which tlie ' jxreat earth-rent of X"eo ' u'oin"- deei)
into the rocky crust was produced, is one of these. A sudden ßdl in g of
the Valœozoic strata on the ri(jht n-ing alomj ilte line of tlie ''Jdidt of Xeo,'
accompanied hi/ hiteral shiftimj toirard tlie nQiih-irest, caused tlie shal^ing
which constituted the hife dreadful catastrophe of Mino, ( hrari, and Ecl>.i:en.

I wish here to express my thanks to Professors Edward Divers
and Dairoku Kikuchi for their kindness in undertaking a laborious
and time- wasting work to see the paper through the press.

April, 1892. Geological Institute of the College of Science.

* Misfiion d'Aiidaloufii' : FJudfs^ rehibiren an tvcmhlcDicnt du tirrf du '!■'). Dt'irnihn' 1SS4, Mcik.
Acad, des Science>t, T, XXX.

PLATE XXVIII.

Plaie XXVIII.

This plate is intended to show the geological formations and stvuctui'es, in general
of the Mino-Owari plain ; the positions of the line of section a-b,and c-d
are indicated with corresponding letters by the heavily dotted (red) lines
in Plate XXIX.

The upper section a-b, representing Palaeozoic formations, is drawn from Yamasaki
in Owari through the ridges of Yörö and Fujiwara to Yominadö in Omi.

SC, — sandstone and clnyslato ;
L, — limestone ;

Q, — qnartz-porphyry ;
GE, — o-ranite.

The lower section c-d, likewise of the Palreozoic complex, is taken in a north,
Avesterly direction from Yamagnchi near Gifii along the Neo valley np to
Haku-san. The rock represented are the sandstone and clayelate, hornstone
and fossiliferous limestone ; the mass of Haku-san being made up of
granite-porphyry.

Koto, Earthquake.

Jour. Sc. Coll. Vol. V. PI. XXV III.

Sntfr — jfinnoo VrffirH

NW ''^t

^ ^ SE

Srtlff — 'I'.OIXI

PLATE XXIX.

Plate XXIX.

Topographic map, pnblislied by the Geological Survey, representing the earth-
quake district of Central Japan between the Japan Sea and the Bay of Isc The
heavy red line indicates the course of the great fault from Katabira in Mino to Fukui
in Echizen, the shaded portion being the meizoseismic area. The dotted lines A-B,
and C-D show the direction of sections, given separately in PI. XXVIII.

1^1

iOi{

Mill' J - jiMBuri

5! H H^r -

^ i i? Ç s ^ ç Î. s - ■

PLATE XXX.

Plate XXX.

General plan for the geological structure of Mino, Owari, and Ecliizen, in wLicli
are shown the regular course (blue lines) of valleys from N. W. to S. E., indicating
the positions of the pro-existing transverse fault, and the black lines being the
direction of the strike of Pahçozoic complex, with the dips as marked with the arrow-
heads. The heavy red line is the course of the ' great fault of Neo".

Kntô, Earthquake.

Jour. So. Goll, Vol. V. PI. XXX.

o Fukui

MlNO-OWARl PLAIN

1=

oNa^(n"a

Faffff-L('/ie.

Sùike of Pa/<ffoz<>rr /^orAs.

PLATE XXXI.

Plate XXXr.

The upper picture slio\Ys thatched roofs fallen intact, and it \Yas in this manner
that most of farmers' cottages gave way, presenting the appearance of gigantic
saddles, when seen from a distance.

The lower picture is the representation of the hanks of the Shonai-gawa near
Biwashima, a suhurh of Nagoya, fractiirod for a mile's length, parallel to the course of
the river.

Koto, Earthquake.

Jour. Sc. Coll. Vol. V. PL XXXI.

Fisc. 1

Fi-. 2

Collotype by K. OGAWA.

PLATE XXXII.

Plate XXXII.

Fin. 1. — A view of Kitakata (5 kilometres west of Gifa) after tlie earthquak'e,
sliowiiic; the rows of lioiises thrown over hy shocks, and the, road became
simply a narrow lane between two interminable heaps of ih-hris.

Fio. 2. — A very strancje hoi'izontal shifting; of earth along the Shönai-c^awa, near
Nagoya, by which the cjronnd toojether with a lari^o bamboo grove and a
fallen thatched roof slid bodily some sixty feet westwards, the bamboo
grove and a few pine trees remaining upright.

Koiô, Earthquake.

Jour. Sc. Coll. Vol. V. PI. XXXII.

FiîT. 1

Fig. 2

Collotype by K. OGAWA.

PLATE XXXIII.

Plaie XXXIII.

Tiie map of tlie iieigUbourhooJ of Kamamoto in tlie islau 1 of Iviü-shü, compiled
by myself from various sources. It shows the seat of source of tlie earthquake iu
1889, in the extinct volcano of Kimposan (Kibo-zan) with an old somma around it.
A-B, C-D, and C-E are the lines of fissure, formed at the time of the severe shocks ;
the shaded (blue) portion being the meizoseismic area in which buildings had been
all more or less damaged. A portion of the city of Kumamoto, shaded in red, had
been intensely shaken, on -ticcount of its being once marshy ground of which we
have many historical proofs.

Koto, Earthquake.

Jour. Sc. Coll. Vol. V. PI. XXXIII.

MAP

OF THE 7

ENVIRONS OF RmiAMOTO

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PLATE XXXIV.

Plate XXXIV.

Amongst the extraordinary works clone by the earthc^ialœ, the fault in Midor
is the most remarlcable. A line new road had been oblitjuely cut into two, and the
west half with the surrounding fields had .sunk about 6 metres below the upper end.
The eastern half had been pushed 4 metres northwards, as is well seen in the
photograph by an abrupt change in the direction of the displaced road.

Koto. Earthquake.

Jour. Sc. Coll. I'oi. r. PI. xxx/r

CuLLurvrE BY K. üGAWA.

Plate XXXV.

TLe ploiigli-sliare-like appearancô of fault near Fiijitani in tLe Xeo valley,
aloug whicli again the depressed eastern Aviug, in conformation to the general rule,
had been shifted in a northerly direction.

Koto, Earthquake.

Jour. Sc. Coll. Vol. V. PL XXXV.

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Collotype by K. OGAWA.

MBL WHOI LIBRARY

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