Rodolfo Amedeo Lanciani.

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al, a2, &c. They are only connected with the arms to this ex-
tent, that these latter lie back upon them. The arms are pro-
vided with pinnulae but it is not at all certain that they (the pin-
nulae) were in any direct communication with the hydrospires.
It is evident that in all the Cystidea^ (and in none is it more ob-
vious than in Caryocrinus\ there was no connection between
the hydrospires and the pinnula). The main difference (so far
as regards the evidence of the presence or absence of such a
connection) between Caryocrinus and Codaster ^ consists in this,
that in the former the arms are erect and do not touch the hy-
drospires, whereas in the latter they are recumbent and lie back
upon them. Each of the arms of Codaster has a fine ambula-
cral groove and all of the grooves terminate in a single central
aperture. But as this aperture was covered over by a thin plated
integument, as in the Blastoidea, I have not shown it in the
dia^am, but only the five pores, p.

No one who compares a Codaster with a Peniremites (the in-
ternal structure of the latter being visible) can doubt that the
hydrospires of the two genera are perfectly homologous organs.
If we grind off the test of a species of the latter genus, selecting
one for the purpose which has broad petaloid ambulacra such as
those of P. Schultziiy the structure exposed will be that represen-
ted in the diagram, fig. 3. In Pentremites as in Codaster^ the five
hydrospires are divided into ten equal parts by the five rays,
al, a2, &a In Codaster these ten parts remain entirely separate
from each other, but in Pentremites they are re-united in pairs,
the two in each interradial space, being so connected, at their
inner angles, that their internal cavities open out to the exterior
through a single orifice or spiracle (5, figs. 3 and 4). This is
best snown in fig. 4, intended to represent the structure of P.
elkpticus (Sowerby) as described by Mr. Rofe, GeoL Mag., voL
ii, p. 249, In this species the hydrospires instead of being



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E, Billings on the structure of the Crinoidea^ etc, 55

formed of broad sacks, with a number of folds on one side, con-
sist of ten simple cylindrical tubes connected together in live
pairs. The only difference between the structure of fig. 3 and
fig. 4 is in the width of the tubes and in the absence of folds
in the latter. These two forms are moreover connected by inter-
mediate grades. Species with 11, 10, 8, 6, 5, 4 and 2 folds be-
ing known, there is thus established a gradual transition from
the broad petaloid form to the single cylindrical tube.

Between the Cystidea and the Blastoidea the most important
changes are, that in the latter the hy drospires become connected
in pairs, and, also, are brought into direct communication with
the pinnulse. In the Palaeozoic Crinoidea (or at least in many of
them) concentration is carried one step further forward, the five
pairs of hydrospires being here all connected together at the
centre as m fig. 5. There is as yet no oesophageal ring, (as I
understand it) but in its place the convoluted plate described in
the excellent papers of Messrs. Meek and Wortnen This organ,
according to tne authors, consists of a convoluted plate, resem-
bling in form the shell of a Bulla or Scaphander. It is situated
within the body of the Crinoid with its longer axis vertical and
the upper end just under the centre of the ventral disc. Its
lower extremity approaches but does not quite touch the bottom
of the visceral cavity. Its walls are composed of minute poly-
gonal plates or of an extremely delicate network of anastomos-
ing fibres. The five ambulacral canals are attached to the upper
extremity, radiate outward to the walls of the cup and are
seen to pass through the ambulacral orifices outward into the
grooves of the arms. (Ante, voL xlviii, p. 31.)

The ambulacral canals of the Crinoidea are, for the greater
part, respiratory in their function. They are, however, as most
naturalists who have studied their stricture will admit, truly
the hoiQologues of those of the Echinodermata in general In
the higher orders of this class the canals are usually more spe-
cialized than they are in the lower ; being provided with pre-
hensive or locomotive organs. In all of the existing orders,
including the recent Crinoidea, we find an oesophageal ring.

To this organ, which is only a continuation of the canals, are
attached the madreporic appendages. These consist of small
sacks or slender tubes varying greatly in form and number in
the different genera. That of the Starfish Asteracanthion rvbens
is thus described by Prof E. Forbes. " On the doraal surface is
seen a wart-like striated body placed laterally between two of
the rays : this is the madreporiform tubercle or nucleus. When
the animal is cut open, there is seen a curved calcareous col-
umn running obliquely fk)m the tubercle to the plates sur-
rounding the mouth ; Dr. Sharpejr says it opens by a narrow
orifice into the circular vessel. It is connected by a membrane



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56 E. Billings on the structure of the Crinoidea, etc.

with one side of the animal, and is itself invested with a pretty-
strong skin, which is covered with vibratile cilia. Its form is
that of a plate rolled in at the margins till they meet It feels
grixty as if full of sand. When we examine it with the micro-
scope we fitid it to consist of minute calcareous plates, which
are united into plates or joints, so that when the invest-
ing membrane is removed it has the appearance of a jointed
column. Professor Ehrenberg remarked the former structure,
Dr. Sharpey the latter : they are both right Both stinictures
may be seen in the column of the common cross-fish." (Forbes,
British Starfishes, p. 73.)

In Prof Joh. Miiller's work, " Uber den ban der Echinoder-
men," several forms of the madreporic appendages of the different
groups of the recent Echinodermata are described. In gen-
eral they are composed of a soft or moderately hard skin con-
sisting of a minute tissue of calcareous fibres, or of small poly-
gonal plates. The walls are also, sometimes, minutely porif-
erous. In all the Holothurians the madreporic organ is a sack
attached by one of its ends to the oesophageal canal, the other
extremity hanging freely down into the perivisceral cavity, not
connected with the opposite body wall as is the sand canal of
the starfishea (Op. cit, p. 84.) In its consisting of a convolu-
ted plate the madreporic organ of Actinocrinus^ therefore, agrees
with that of the starfishes, while in its being only attached at
one extremitv it resembles that of the HoloSiurians.

The convoluted plate of the Palaeozoic Crinoids and the mad-
reporic sacks and tubes (or sand canals) of the recent Echino-
derms, therefore, all agree in the following respects : —

1. They have the same general structnra

2. They are all appendages of the ambulacral system.

8. They are all attached to the same part of the system, that
is to say, to the central point firom which the canals radiate.

The above seems to me suflScient to make out at least a good
prima fade case for the position I have assumed. When among
the petrified remains of an extinct animal, we find an organ
whicn has the same general form and structure, as has one wiat
occurs in an existing species of the same zoological group, we
may, with much probability of being correct in our opinion,
conclude that the two are homologous, even although we may
not be able positively to see how that of the fossil is connected
with any other part But when, as in this instance, we can ac-
tually see that it is an appendage of another organ, or system of
organs rather, which is Known to be the homologue of the
part with which that of the existing species is always correlated,
we have evidence of a very high order on which to ground a
conclusion. By no other mode of reasoning can we prove that



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E, Billiiigs on the structure of the Crinoidea^ etc. 57

the column of an Actinocrinus is the homologue of that of Pen-
tacrinus caput Medusce.

In an important paper entitled " Remarks on the Blastoidea,
with descriptions of New Species" which Meek and Worthen
have kindly sent me, the authors, in their comments upon my
views, state that : —

" In regard to the intemal convoluted organ seen in so many of the AcHnocridcB
belonging to the respiratory instead of the digestive system, we would remark that
its large size seems to us a strong objection to such a conclusion. In many instances
it so nearly fills the whole intemal cavity that there would appear to be entirely
inadequate space left for an organ like a digestive sack, outside of it, while the
volutions within would preclude the presence of an independent digestive sack
there. In addition to this, the entire absence, so far as we can ascertain, of any
analogous, intemal respiratory organ in the whole range of the recent Echinoder-
mcUa, including the existing Crinoids, would appear to be against the conclusion
that this is such, unless we adopt the conclusion of Dujardin and Hup^, that the
Palaeozoic Crinoids had no internal digestive organs, and were nourished by absorp-
tion over the whole surface. We should certainly think it far more probable that
this spiral organ is the digestive sack, than a part of a respiratory apparatus."

The objection here advanced does not appear to me to be a
strong ona In many of the lower animals the digestive organs
are of inconsiderable size in proportion to the whole bulk. In
the Brachiopoda, for instance, the spiral ciliated arms fill nearly
the whole of the intemal cavity, the digestive sack being very
small and occupying only a limited space near the hinge. These
arms, although not the homologues of the convoluted plates of
the Palaeozoic Crinoids, have a strong resemblance to them, and
are, moreover, at least to some extent, subservient to respiration.
They are certainly not digestive sacks. In the recent echino-
derms the intestine is usually a slender tube with one or more
curves between the mouth and the anus. It fills only a small
part of the cavity of the body, the remainder being occupied
mostly by the chylaqueous fluid, which is constantlv in motion
and undergoing aeration, through the agency of various organs,
such as the respiratory tree and branchial cirrhi of the Holo-
thuridea, the dorsal tuouli of the Asteridae and the ambulacral
systems of canals of the class generally. In no division of the
animal kingdom do the respiratory organs occupy a larger pro-

?)rtion of the whole bulk than they do in the Echinodermata.
he great size which the convoluted plate attains in some of
the Crinoids is, therefore, rather more in favor of its being a
respiratory than a digestive organ.

Professor Wyville Thomson says that inside of the cavity of
the stomach of the recent Crinoid, A niedon rosdceus^ there is a
spiral series of glandular folds which he supposes to be a ru-
dimentary liver. (PhiL Trans. R S., 1865, p. 625). It is barely
possible that the convoluted plate may represent this organ.
At present I think it does not
I believe that the reason why the convoluted plate attained



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58 J. C. F. Zidner on a new Spectroscope.

a greater proportional size in the Palaeozoic Crinoids, tlian do
the sand canals of the recent echinoderms, is that the function
of the system of canals (of which they are all appendages,) was
at first mostly respiratory, whereas in the greater number of
the existing groups, it is more or less prehensive or locomotive,
or both.

[To be coDtinued.]



Art. Vni. — Upon a new Spectroscope^ with Contributions to the
Spectral Analysis of the Stars ; by Dr. J. C. F. ZoLLNER.*

Stellar spectrum analysis, in addition to its revelations
concerning the physical constitution of the heavenly bodies,
has begun most recently to claim attention in an increasing
degree in another no less interesting direction. With the aid
of this method the prospect is presented of proving, and under
favorable circumstances also of measuring, what influence is
exerted on the lines of the spectrum of a star by the compo-
nents of the relative motion of the earth and star along the
line uniting the two bodies.

A single consideration shows that effects which two separated
bodies exert upon one another by means of a periodical impulse
of a limited rapidity of propagation must be modified oy a
continual change of the distance separating them. It is Dop-
pler's merit to have first, in the vear 1841, recognized the
necessity of this influence,f although the conclusions which he
derived from it with respect to the color of the stars must be
acknowledged as incorrect by reason of a disregard of the invis-
ible parts of the spectrum.

With reference to sound this influence was proved to be con-
formable to the demands of theory by numerous experiments
of Ballot, Mach and others.

On the contrary with reference to light it has not been pos-
sible hitherto to establish by observation a trustworthy value
(sicher nachweisbare Grosser) of this influence, because even the
cosmical movements, which are the greatest at our disposal for
this object, are very small in comparison with the rapidity of
the propagation of light.

The great improvement however, which optical instruments
for the observ tion of spectra have experienced since the dis-

* From the Proceedings of the Royal Society of Sciences of Saxony at
Leipzig, Session of Feb. 6, 1869. Translated by A. N. Skmner, assistant at the
. Dearborn Observatory, Chicago, Illinois.

f Doppler, " On the colored light of double stars and of some other stars of the
heavens." Transactions of the Bohemian Society of Sciences, vol ii, (1841-42) p.
465-482.



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J. C, F. Zbllner §n a new Spectroscope, 59

covery of spectrum analysis, presents the prospect of demon-
strating this influence by the spectra of the stars. According
to theory this influence must show itself in a small displace-
ment of the lines of the spectrum. For example, for a mean
velocity of the earth of four German miles per second, this
displacement would amount to the tenth part of the distance
separating the two sodium lines. This value which is obtained
in a very simple way from the velocity of light and the undu-
lation-time of the rays corresponding to the sodium lines, has
only quite lately been derived again by J. C. Maxwell, in agree-
ment with earlier computations by F. Eisenlohr* and others.

The amount to be observed of the displacement appeared,
however, to Maxwell to be so small, that he closed his conside-
rations concerning this (having reference to the spectroscope
hitherto constructed and the method of determining the posi-
tion of the lines), with the remark : '* It cannot be determined
by spectroscopic observations with our present instruments,
and need not be considered in the discussion of our observa-
tions, "f

Huggins nevertheless in his most recent memoir,:|: of which
the above mentioned investigations of Maxwell are an inte-
gral part, attempted the solution of the problem in question
by the use of a spectroscope with no less than five prisms,
of which two are Amici's, with two flint and three crown-glass
prisms.

The diminution of the light caused by so great a number of
prisms permits, however, the observation of only the brightest
stars. Huggins indeed even confined himself to the communi-
cation of his results from observations on Sinus, and he believed
here that he found a small displacement of the line F in com-
parison with the bright hydrogen line produced by a Geissler's
tube. The direction and amount of the displacement would
indicate an increase in the distance between the earth and Sirius,
and this with a velocity of 411 English miles per second.

If we eliminate the component of the earth's movement, which
at the time of observation amounted to 12 English miles, the
resulting velocity with which the sun and Sirius are moving from
one another would be 294 English miles, or about 6*5 German
miles.

Huggins himself regards this result as one affected by great
probable error, an error caused partly by the great weakening
of the light, already mentioned, from numerous prisms, and
partly by the difficulty of comparing the coincidences of the
bright lines from terrestrial sources of light with the analogous
dark hnes of stellar spectra. The latter have sometimes a dif-

♦ Heidelberg Transactions of the Phys. Med. Soc., vol. iii, p. 190.
t PhiL Trans., 1868, p. 632. J Ibid., p. 535.



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60 J. C. F, Zbllner on a new Spectroscope,

ferent appearance ; for example, they are blurred on the edge
and of aiflferent breadth, as is precisely the case with the line F
in the spectrum of Sirius.

The most essential of these difficulties, which have hitherto
opposed a definite solution of the problem in question, I believe
that I have successfully overcome, by a new construction of the
spectroscope, the first example of which I have the honor to
exhibit here to the Royal Society.

The arrangement is in essentials the following. The line of
light produced by a slit, or a cylindrical lens, lies in the focus of
a lens which as in all spectroscopes renders parallel the rays to be
dispersed. Then the rays pass through two Amici's direct- vis-
ion prism-systems of excellent quality, which I obtained from
the optical establishment of Merz in Munich.

These are fastened to one another in such a manner that
though each passes one half of the pencil of rays proceeding
fi-om the collimator object-glass, and also so that the refracting
angles lie on opposite sides. In this way the collected pencu
of rays will be dispersed in the two spectra in an opposite di-
rection. The object-glass of the observing telescope, which
unites the rays again to an image, is perpendicular to the re-
flecting angles of the prisms placed horizontally, and as in the
heliometer, is divided ; each of the two halves can be moved
micrometrically both parallel to the line of section and perpen-
dicular to it. By means of this we can bring the lines of one
spectrum into coincidence with those of the other, and also place
the spectra in immediate juxtaposition instead of superposing
them, so that one spectrum moves by the other like a vernier,
or we can superpose them only partially. By means of this
construction not only is the delicate principle of double-images
rendered available for the determination of any change what-
ever in the position of the lines of the spectrum, but any such
change is also dovhled^ since its influence appears in the two spec-
tra in an opposite sense.

The principal of the reversion of spectra which lies at the
foundation oi the instrument described, on account of which I
venture to propose for it the name "Reversion Spectro-
scope," can be introduced without using Amici's systems of
prisms. It is only needed to reverse one part of the pencil of
rays proceeding from a common prism by reflection on a mirror
or pnsm, and then to observe the united pencil of rays exactly
as above with a telescope furnished with a divided object-glass.
Furthermore, this principle renders the simultaneous introduc-
tion of artificial sources of light for the investigation of small
changes of refrangibility wholly unnecessary, and permits the
perception and measurement of these changes, by means of the
changes in position of objects completely similar in kind.



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J. C. F, ZbUner on a new Spectroscope, 61

The series of measurements which was carried out both on
the dark D line of the solar spectrum, and also on the bright
sodium lines of a candle flame impregnated with common salt,
(and these I venture to add here to show the working power
of the instrument), authorizes the hope, that with the aid
of this spectroscope we shall succeed not only in perceiving
the influence of the earth's movement, but also in determining
it quantitatively with such accuracy as appears desirable for an
approximate (vorlaiifig) control of theoretical conclusions.

The numbers cited aenote the parts of the micrometer-screw,
and refer to the distance between the two sodium lines :



Soditim flame.


Sun.


49-6


49-6


50-6


51-5


53


48-1


49-6


48-9


60-6=fc0-6


49-6d=0-6



In tlie following series of observations the reversion spectro-
scope was furnished, not only with another micrometer-screw
witn a somewhat coarser thread, but also with two other systems
of prisms whose dispersion in the region of the sodium line is
1-77 times greater than that of the systems used for the above
measurements. Likewise the old achromatic object-glasses of the
collimator and the observing telescope were replaced by un-
achromatic ones, by which not only nothing was lost in shjapness
of the im^es, but, as was designed, an advantage was gained
in clearness and distinctness by increasing the intensity of light





Sun.




Screw divisions.


Deviation fixMn mean.


671




— 0-8


69-4




+1-5


68-4




-fO-6


67-9




0-0


66-6




-1-3


66-1




—1-8


68-2




+0-3.


680




- 0-1


69-6




- 1-7



Mean 67-9dbO-3

According to this, the interval between the two D lines was
accurately determined, with a probable error of ^^^ of its valua
But in accordance with facts previously presented, a change of
the distance separating the source of light and the spectroscope,
with a velocity of four German miles per second, will effect a
corresponding displacement of the lines of the two spectra, to
the amount of \ of the interval of the D lines, a quantity which



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62 J, C. F. Zollner on a new Spectroscope,

is also about forty times greater than the probable error found
above for the mean of nine readings.

If, therefore, in the observation of stellar spectra, a sufficient
amount of light can be used, it can be definitely determined in
the way stated, whether the expected displacement of the lines
of the spectrum occurs or not. In reference to the intensity of
light req uired, I venture to remark, that, for these observations,
an unacnromatic lens* of one Paris foot in aperture and six feet
focal length is at our disposal ; its cone of rays one inch from
the focus is acted upon by a suitable concave meniscus of flint-
glass, and, freed thus as much as possible from spherical and
chromatic aberration, is directed to the slit of the spectroscope.
I feel that I should here especially point out the fact, that, .in
the use of a slit, the achromatism of the optical image, for the
observation of its spectrum, (especially of individual parts of
it), is unessential, and consequently the construction indicated
here must claim the important preierence of great cheapness in
comparison with those with achromatics of strong light Evi-
dently this advantage must be given up in those cases, where,
as in double stars, the desideratum is the sharpest possible sep-
aration of the objects under investigation.

I may be permitted perhaps to make some remarks upon
problems and methods which refer to spectrum observations on
the sun and with which I am at present employed.

The sun possesses a velocity of rotation, by virtue of which
a point on its equator moves with a velocitv of about 0*25 Ger-
man mile. If, therefore, with the aid. of a heliometer, or in any
other way, we produce a double image of the sun, and by a
suitable arrangement bring into contact two points of the equa-
torial limb, then at the point of contact, parts of the sun's sur-
face border upon one another, one of which approaches us with
a velocity of the given amount, and the other recedes from us
with the same velocity. From this arises a difference of velo-
city of the parts in contact, in the direction of the line of sight,
of about half a German mile. According to previous state-
ments such an amount of movement would cause a change of
position of the sodium lines corresponding to the 80th part of
the interval between them. Therefore if by combination of a
sufficient number of prisms, we succeed in perceiving such a
quantity, so as to measure it, we need only to bring the middle
of the slit into the line joining the two centers of the images of
the sun which are tangent to each other in order to see the
two spectra of the sun's limbs which are thus in contact, close
together in the field of view, and then, under the most favora-
ble relations, to observe the displacement in question. In this
way then the position of the solar equator, and, in case of the
* Made in the optical establishment of H. Schroeder in Hamburg.



Online LibraryRodolfo Amedeo LancianiThe American journal of science and arts → online text (page 8 of 109)