C8
PROKKSSOll LANKE3TER.
The BED VASCULAR FLUID of the EARTHWOMI a COUPTJSCULATED
FLUID. By E. RAY LANKESTER, M.A., F.R.S.
IN describing the anatomy of the Earthworm in the sixth
volume of this Journal some years since, I made the statement,
which was in agreement with the current opinion, that the red
vascular fluid of that animal is free from corpuscles. This statement, like several others contained in the same essay, is erroneous.
I am happy in this case to be able myself to furnish a more correct account of a feature in the organisation of the Earthworm
which, however small and insignificant in point of fact, has yet
been the subject of much discussion and speculation.
Our positive knowledge of the significance of the red vascular fluid
of Chsetopodous worms was materially advanced by Nawrocki's
demonstration in 1867, that the colouring matter of this fluid in
the Earthworm is haemoglobin—a discovery which I independently confirmed and extended by spectroscopic observation of
other Chzetopoda ('Journal of Anatomy/ 1867, p. 114; ibid.,
1869, p. 119, and ' Proe. Roy. Society,' 1873, No. 140.) The
fact, however, that abundant corpuscles are present in this same
fluid in the case of the Earthworm (and as appears very probable
in all similar fluids) has hitherto escaped detection, owing to the
difficulties of observation which small corpuscles floating in a
deeply coloured liquid present, and also to the fact that the method
by which they may be rendered apparent has not been applied
to them by the various observers who have occupied themselves
with this matter.
The gifted and laborious investigator of the anatomy of
the ChBetopoda, Edouard Claparede, so far anticipated the observation which I have made in the case of Lumbricus, as to
discover in the red vascular system of Cirrhatulus, Ophelia,
and Staurocephalus (identical in its general anatomical features
with that of Lumbricus), floating histological elements or corpuscles. He says in his introduction to' Les Annelides Chetopodes du Golfe de Naples/ p. 19, " L'existence de corpuscles
du sang dans les vaisseaux de certaines Annelides est ajcurdhui
indubitable. M> de Quatrefages, dans son Eistoire des
Annele's, en admet trois exemples; les Glyceres, les Phoronis,
et les Syllidies. Ce dernier seul a de la valeur. En effet chez
les Glyceres, les corpuscles rouges appartiennent tu liquide de
la cavite periviscerale, et quant aux Phoronis, elles ne pourront
guere conserver leur place parmi les Annelides. Mais, sans parler d'une ancienne observation de Rud. Wagner relative k une
Terebelle, observation d'ailleurs confirmee par M. Kolliker, on
RED VASCULAR FLUID OF THE EARTHWORM.
69
peut en citer d'autres exemples. Dans ce memoire, ou trouvera
des corpuscles sanguins proprement dits, decrits chez les Ophelies, chez les Cirratuliens, chez les Stauroce"phales."
The same zoologist, however, in his classical' Histologische
Untersuchungen iiber den Regenwurm,' published in 1869, explicitly affirms the absence of such corpuscles from the vascular
fluid of the Earthworm. Speaking of the remarkable spherical
dilatations of the blood-vessels which occur on the walls of the
segmental organs or nephridia and in other parts, he writes what
is here translated, "The structure of these dilatations of the
vessels is of such a nature that it is not possible to regard them
as accidental. Gegenbaur, moreover, says that he has always seen
them filled with a red coagulum enclosing blood-corpuscles.
Lankester also saw a granular matter within them. In point of
fact I find in them constantly a quantity of nuclei, which in all
probability are derived from the division of an ordinary nucleus
of the vessel's wall. Such nuclei I am unable to regard with
Ge.geubaur as blood-corpuscles, since it is a well-known fact that
Hood-corpuscles are absent from the Earthworm."
The statement made by Gegenbaur, and here referred to,
occurs in his article " Ueber die sogenannten Respirations-organe
des Regenwurms " in the ' Zeitsch. fur Wiss. Zoologie,' 1852,
vol. iv, p. 227. He says "Das Lumen dieser Anscbwellungra
stellte sich tnir fast immer mit eiuein rothen, Blutkorperchen
einschliessenden coagulum ausgeftillt dar." The blood-corpuscles thus recordel by Gegenbaur are those only of the vascular
dilatations which differ in character from those which 1 shall
describe below, and though clearly entitled to rank as bloodcorpuscks or corpuscles of the red vascular system, are peculiar
and apparently confined to these dilatations.
By various writers the absence of corpuscles from the vascular
fluid of the Chsetopoda has been considered a sufficient objection
to the use of the word ' blood' in reference to that fluid, and it
has been spoken of as a ' pseud-haemal/ as distinguished from
a true ' haemal' fluid. A variety of views have also been put
forward at different times as to the relationships of this fluid
and the vessel which contain it, and of the perienteric or peritoneal corpusculated fluid, to the ' blood' of Mollusca, of Arthropoda and of Vertebrata. Gegenbaur, in his ' Grundziige der
vergleichenden Auatomie/ 2nd edition, 1870, p. 231, in describing the existence of a fluid contained in a distinct vascular
system, and of another fluid occupying the body-cavity in the
Nemertine worms says, " W e shall speak of this latter as chjlus,
of that contained in the closed vascular system as blood."
Further on (p. 233) lie applies the same nomenclature to the
similar fluids of the Chsetopoda, with which the somewhat dif-
70
PROFESSOR LANKESTER.
ferent vascular apparatus and fluid of the Hirudinea is associated.
Taking thus a comparative view of the blood and blood-vessels
of the Chsetopoda, Gegenbaur was led, especially by a consideration of the condition of the Leeches, where (with the exception of
Branchiobdella) the vascular system and perienteric system are
in open communication, to attach little importance to the recorded presence or absence of corpuscles in the blood (vascular
fluid) which he held to be only a portion of the general liquid
of the body cavity which had been gradually differentiated.
Professor Huxley, in his ' Manual of the Anatomy of Invertebrated Animals, 1877/ p. 219, writing of the oligochsetous
Chsetopoda, says, " In addition (to the colourless corpusculated
fluid of the perivisceral cavity) there is a system of pseud-bsemaL
•vessels like those of the leeches, provided with contractile walls,
and containing a red, non-corpusculated fluid. No communication has been ascertained to exist between these vessels and the
perivisceral cavity; but there can be little doubt that, as in the
case of the leeches, they must be regarded as a specially differentiated part of the general system of the perivisceral cavity."
Further on (p. 223), in the course of an admirable description
of the anatomy of the Earthworm, he say, " A colourless fluid,
containing colourless corpuscles, and answering to -the blood of
other invertebrated animals, occupies the perivisceral cavity; but,
in addition to this, there is a deep-red fluid, devoid of corpuscles, which fills a very largely developed system of pseudhsemal vessels."
In a book entitled 'Forms of Animal Life/ published at
Oxford in 1870, by Dr. George Rolleston, Professor of Physiology in that University, there are two references to the
presence and abseixeof corpuscles in the vascular system of Annulate worms. At page 124 the writer states that the vascular
system of the Earthworm "is called 'pseud-haemal/ because,
though the fluid which it contains is coloured and probably
respiratory in function, it is not corpusculated, and, therefore,
not morphologically blood." The morphological definition of
' blood' here assumed is clearly another one than that adopted
by Gegenbaur. By Gegenbaur the specialisation of a portion of
the general body-cavity (ccslom) and its contained fluid fur
respiratory or nutrient Junctions or both, in the form of a distinct
system of vessels coexistent with the undifferentiated portion, is
regarded as the formation of 'blood-vessels' and ' blood.' By
Dr. George Rolleston the presence of corpuscles in the differentiated fluid is held to be necessary in order that it may rightly
be called * blood/ The second reference to this subject in this
physiologist's treatise is on page cxxix, and scarcely tends to
explain the importance which he attaches to a strict morpholor
RED VASCULAR FLUID OP THE EARTHWORM.
71
gical definition of the term blood. He says, " I n a few annelids,
again (Sgllidea armata, the Ophelia, the Cirratulida, and the
Staurocephali and Branchiobdella), the so-called pseud-haemal
system contains corpusculated blood, and communicates with the
perivisceral cavity, so as to form a lacunar circulation." At first
sight this passage would appear to be based upon the statements
of Claparede,1 above quoted, with the omission of the important
case of Terebella and the addition of Branchiobdella. So far as
the fact of the presence of corpuscles is concerned, this appears
probable enough.
The entirely original introduction of Branchiobdella into
the list of Annulata with corpusculated " pseud-hseinal fluid"
is difficult to explain, since from what follows it seems unlikely that Dr. George Eolleston had made himself acquainted
by actual observation with any of the genera to which he alludes.
On page 238 of the second edition of Gegenbaur's ' Grundzuge'
a somewhat awkwardly introduced reference to Dorner's paper
on Branchiobdella might lead an unwary reader to suppose that
the statements there given on the authority of Kupffer and Leydig,
with reference to the proliferation of blood-corpuscles from
the valves of the vessels in other leeches (Piscicola and Clepsine),
have reference to Branchiobdella, which they have not. A
glance at Dorner's excellent memoir on Branchiobdella would,
however, suffice to satisfy a conscientious bookmaker that the
vascular fluid of Branchiobdella has not yet been shown to contain corpuscles, and that it notoriously differs from the vascular fluid of true leeches, in that it most certainly does not " communicate with the perivisceral cavity, so as to form a lacunar
circulation." The introduction of Branchiobdella into the list
1
The observal ion of corpuscles in the blood of Syllidia armata is due to M.
de Quatrefages. The hasty appropriation of a citation of one author made by a
second, is liable to lead a third author into error. The curious information as
to a lacunar circulatioh in Syllidia, which is imparted to students in the passage
extracted from the ' Forms of Animal Life,' is a direct contradiction of
the statement of M. de Quatrefages himself, whose accuracy with regard
to the corpuscles appears nevertheless to be admitted, siuce his statement
on that matter is made use of by the writer. It does not appear possible
that the writer of the ' Forms of Animal Life,' can have read the original
statement of M. de Quatrefages quoted below. He appears to have been
content to avail himself of a passing reference made by a third person, viz.
M. Claparede. M. de Quatrefages writes ('Histoire des Annele's,' tome ii,
1865, p. 15) in reference to Syllidia armata:—" J'ai vu nettement deux gros
vaisseaux contractiles, ii parois assez irregulieres, places sur la ligne m6diane,
Tun au-dessus, l'uutre au-dessous du tube digestif. Us sont mis en communication par des branches latcrales a la hauteur de chaque pied ; mais je n'ai
pu distinguer de ramifications proprement diles. Si elles avaient exisle,
elle ne m'auraient probahlement pas echappe, car, coinme je l'ai deja dit,
par une exception fort rare chez les Aunelides, le sang renfcrme ici des
globules bien caracteris^s."
72
PROFESSOR 1ANKESTEU.
given by Dr. George Eolleston is, it would seem, due to his
having misunderstood the German authors.
The statement that " the pseud-hsemal system communicates
with the perivisceral cavity so as to form a lacunar circulation"
in Syllidia, the Ophelim, the Cirratulida, and the Staurocephali,
is more difficult to account for than is that relative to Branchiobdella, since, whilst there is here also no foundation whatever for
such a statement in fact, the description and figures of Claparede
with reference to two at least of these genera are admirable in
clearness and detail. We are driven to the conclusion that
Dr. George Rolleston has acquainted himself with the introduction, without having consulted the body, of Claparede's work.
The blood vascular system of Syllidia, Ophelia, the Cirratulida, the Staurocephali, and the Terebellse, is a closed system
and contains blood in which float corpuscles. These corpuscles
are colourless and are not to be confused with the colourless
corpuscles existing in the open vascular system of the true
Leeches, nor with the corpuscles coloured red by haemoglobin
which exist in the perienteric fluid of the anaugian genera
Glycera and Capitella. Corpuscles similar to these last are met
with in the vascular fluid of some few Nemertines, in Phoronis,
in the single blood-lymph fluid of the Lamellibranchs, Area and
Solen (one species), and in the blood of Vertebrates.
Whilst I regret to find myself unable to accede to the statements in the text-book which I have quoted above, I may point
out that the errors therein contained are not traceable to any
attempt on the author's part to make original observations
in the domain of
morphology, but are rather due to a fuilure
to observe accurately the contents of books.
The corpuscles of the red blood of the Earthworm are
abundant in the largeT and even in the finest branches of the
vascular system. They are flattened, fusiform bodies, usually
somewhat broader at one end than the other, sometimes nearly
circular. They vary in size from the T r W ^ ' ° *he ac/ooth of
an inch in long diameter, but by far the majority are of a uniform
length of about 3- 0'0 0-th of an inch. The corpuscles have a clean,
sharp outline, but occasionally what appears to be a small quantity of ragged protoplasm is seen beyond this sharp contour.
They are colourless, but stain feebly after treatment with dilute
osmic acid followed by picrocarmin. A small centrally placed
granule receives, when the corpuscles are thus treated, a deep
staining. Prom a comparison with the structures presented by
the walls of the vessels in which these corpuscles occur, it is
clear that they are the nuclei of the endothelial cells set free
RED VASCULAR FLUID OF THE EARTHWORM.
73
from the walls of the vessels, whilst the granule which takes
a deep staining from picrocarinin is the nucleolus.
In fresh blood-vessels of the Earthworm I have not succeeded
in observing the blood-corpuscles. Their small size and delicate
character suiRces to conceal them in the red-coloured fluid where
they float. I first detected them in specimens of the tissues of
the earthworm which had been treated with a -ruth per cent,
solution of osmic acid for half an hour, washed with dilute
alcohol, and then stained whilst still under the covering glass by
a solution of picrocarmin, and subsequently clarified by
glycerin. After such treatment, the finer vessels of the muscular septa and of the walls of the testicular sacs of the earthworm exhibit very clearly the histological elements of their
walls, whilst the coagulum within the vessels is seen to contain
numerous free corpuscles of the form and appearance above
described. The corpuscles occur in the vessels in masses; frequently a large portion of a vessel will be found free from them,
whilst an adjacent segment is choked with an abundance.
In order to observe the blood-corpuscles of the Earthworm in
the fresh condition it is necessary to remove on to an objectslide a portion of a large vessel by means of two pairs of forceps,
and to allow its contents to escape on to the slide. It is not
possible in this manner to avoid all admixture with the perivisceral
fluid, the corpuscles of which are very abundant and adhere
tenaciously to the tissues bathed by that fluid. It is, however,
quite easy to distinguish the blood-corpuscles or corpuscles of
the vascular fluid from the lymph-corpuscles or corpuscles of
the perienteric fluid by their shape and size. A cleanly prepared
drop of perienteric fluid shows large, colourless, vacuolated corpuscles, with a ragged outline, often produced into filaments, and
provided with a large nucleus; but in such a specimen none of the
peculiar oblong, flattened, homogeneous (saving the granule) corpuscles peculiar to the blood or vascular fluid will be found. Accordingly, when a quantity of the vascular fluid is taken, even
though it be contaminated by a few lymph-corpuscles, it is quite
easy to recognise the small and peculiar blood-corpuscles.
It is my intention to figure the blood-corpuscles of the Earthworm now described, in connection with a description and
illustration of a few other points relative to the histology of
that animal, which Mr. D'Arcy Power has worked out in the
histological laboratory of Exeter College.