HARVARD UNIVERSITY.

LIBRARY

OF THE

MUSEUM OF ar TIVE ZOOLOGY
He ol

GIFT OF

1 bborm M9 AW heck
Trvembe (ae 1924.

ee Mi pe EMERY

.

ty WESTMINSTER | | 5 4: ; vs
ARCHIBALD CONSTABLE AND CO og ohas
— ae WHITEHALL GARDENS ae y

1900 |
$ han

:
"he
J ‘ ‘€
wv
“1

On Melanenchytraeus Solifugus

An Oligochaetous Annelid of the family of the Enchytraeidae.

By CARLO EMERY

In his expedition to Mount St. Elias, J. C. Russell observed on the
Malaspina Glacier numerous specimens of a small black worm, which “literally
covered” the snow before the rise of the sun, and disappeared beneath the
snow as soon as they felt the warmth of the sun rays.’ Russell states that he
never found these worms when the temperature was above freezing point.

The same worms were found again and for the first time collected by
Dr. De Filippi, in the conditions described by Russell. They appeared at
morning and evening ; on foggy days they disappeared later in the morning
and re-appeared earlier before sunset ; but they were never seen in the hours
near mid-day. During the sunny hours, Dr. De Filippi tried digging under
the snow to a depth of about fifty centimetres without finding any. In con-
tradiction to Russell’s statement, he observed these worms also when the
temperature was above freezing point; but during the return journey they
were much less numerous, and only on those spots of the glacier which were
covered with snow.

The specimens which I have used for this study were put directly in
strong alcohol, and are therefore somewhat shrunken ; but the state of preser-
vation of the tissues would have allowed a more complete study of the
structure of this animal, had the specimens been more numerous,” and collected
at a more advanced season.

Most of these specimens were immature ; they had not developed sperm-
ducts or sperm-sacs or spermathecae. In the more mature specimens, the
eggs were minute, and I could not recognise any vestige of female genital
ducts; but one showed a beginning of clitellum development. With few
exceptions they were lacking in the organs which are the most important for
the discrimination of genera and the determination of affinities in this order
of Annelides.

The worm preserved in spirits (Fig. 1) is dark-brown, nearly black.

1 Second Expedition to Mount St. Elias, Washington, 1894, p. 33. Wright (Zhe Ice
Age of North America, London, 1890, p. 44) mentions also worms found on a glacier of
Alaska and properly on Muir Glacier, “in shallower inclosures of the surface, containing
water and a little dirt.” The conditions in which they were observed, very different from
those in which the worm detected by Russell lives, lead me to think that our worm is not
identical to the Melanenchytraeus of the Malaspina, but belongs to a different species.

-? The number of specimens would have been greater, had not a part of the collects
material been lost by accident.-

2

MELANENCHYTRAEUS SOLIFUGUS
Having bleached a specimen by means of a mixture of chlorate of potassium
and hydrochloric acid and mounted it in glycerine, I succeeded in making it
sufficiently transparent to count the segments exactly, to observe the bundles
of chaetae, and to control by examination of the whole animal some results of
the study of microtomic series. :

The colour is due to dark pigmentation of the hypodermis (Fig. 7) ; it is
so intense that limits of cells or their nuclei are not visible on sections if they
are not extremely thin. This fact may depend on the shrinking of the plasm
of the epithelium-cells, under the direct action of strong alcohol. In one
specimen, unfortunately injured in the genital region, I could recognise the
beginning of development of glandular cells in the hypoderm of the twelfth
(clitellar) segment (Fig. 8).

In the cephalic lobe, sagittal sections show a well-marked cephalic pore
(Fig. 3 fc); in the space between this pore and the mouth the hypoderm is
much thickened ; its cells are much elongate, pigmented at their base and
apex only. In this region there are in the hypoderm club-shaped bodies,
strongly pigmented at their superficial part, nearly pigmentless at their deep
or basal part, which shows a large nucleus (Fig. 9 cs). I believe that these
bodies are sense cells, possibly organs of sight; they seem to be connected
with a thick nerve, which arises from the lateral commissure of the cesophageal
ring, and distributes itself in that region (Fig. 2). A more accurate study
of these supposed sense bodies was not possible on preserved material.

The cutaneous pigment was not confined to the hypoderm ; large cells
filled with dark-brown pigment were found around the bundles of chaetae
(Figs. 12, 13, 15) and in their neighbourhood. I was not able to recognise the
precise nature of these cells; each of them has a clear round spot showing
the nucleus. Brown pigment lies also in the end of the nephridial ducts,
_ near their external opening (Figs. 12, 13).

The chaetae are slightly sigmoid, more markedly bent at their apical
end (Fig. 10). They are about a third longer in the posterior half of the
body than in the anterior segments, as it appears by comparing Figs. 12
and 13. Each bundle consists of four nearly equal chaetae. The ventral
bundle is absent in the 12th (clitellar) segment, which receives the opening
of the sperm-duct.

The drain, as I have made out by graphical construction from a series
of sections (Fig. 2), is of nearly quadrate shape, with the anterior margin
slightly concave. From the base of each of the lateral commissurae arises
the large nerve mentioned above, which distributes to the skin of the
cephalic lobe.

In the south-opening the epithelium is for a short tract pigmented
(Fig. 3). Further backward the epithelial cells are pigmentless ; but in
their interstices we find branched cells, filled with granular brown pigment.
In the pharynx, the epithelial cells are very high and hardened at their
superficial end, but without a distinct cuticle; between them lie pigmented
cells with long branches (Fig. 6).

3

MELANENCHYTRAEUS SOLIFUGUS

The pharynx builds a dorsal appendage of the cesophagus, in the 2nd
and in the beginning of the 3rd segment (Fig. 3 4%); its dorsal part gives
insertion to a system of muscular bundles, which suspend this organ to the
walls of the foremost four body-segments. Fig. 4 gives, in a somewhat
schematic form, the graphic reconstruction of these muscles, made from
a series of sagittal sections. The system consists of an anterior and posterior
group. The former arises from the dorsal wall of the Ist and anterior end
of the 2nd segment; the other is more complex and offers two knots, to
which the bundles from the dorsal wall of the 3rd and 4th segments, and a
bundle from the ventral wall of the 4th, converge.

The part of the alimentary canal which follows on the pharynx, and
may be called esophagus, offers no notable widening, and is continuous
without partition with the rest of the gut. The long cilia of the intestinal
epithelium are clearly shown in my preparations (Fig. 5 ez).

I have found in the gut some specimens of an Infusorium of the genus
Anoplophrya (Fig. 18); I could not see cilia on its surface, although the
long cilia were well preserved on the intestinal epithelium in the same
section. The intestine of the same specimens of the worm contained a
number of ovate, brown bodies, closed in a thin membrane, and filled with
clear spherules (Fig. 19 a); some of them were cut by the microtome knife
(Fig. 19 6), and showed in each spherule a grain (the nucleus?), coloured
by carmine. I don’t know whether these bodies have any relation to the
Anoplophrya; they might be incapsulated germs of the parasite.

The intestine,and more markedly its posterior part, is filled with very
fine crystalline mineral detritus, which seems to be the ordinary food of this
worm.

The cells of the chloragogen (Fig. 5) are very long, and build a dense
coating to the intestine.

In the segments 4-8, the most part of the body-cavity is filled by
unicellular glands (Fig. 11 gl); their very thin excretory prolongations form
numerous threads directed towards the ventral side, which can be easily
followed on the sections to the sides of the ganglion chain. Their thinness
and flexuous course make it extremely difficult to follow them to their end
on the surface of the skin. I believe that they converge towards the bundles
of chaetae of the ventral series. As Mr. Michaélsen writes me, these glands
may be regarded as morphological equivalents to those gland-cells which
in other Enchytraeids are related to the chaetae of the genital segments. ©
In Melanenchytraeus, 1 don’t think that these glands have any relation to
the functions of reproduction, because I find them no less developed in
immature specimens.

In some anterior segments, and peculiarly in the 9th and toth, there
are, between the nephridium and the body-wall, clusters of cells (Fig. 12 x)
whose plasma is filled with very minute and strong refracting granules,
rendering them obscure in transmitted light, white in incident light. These
cells are not clearly outlined, and in the middle of each a small round nucleus

4

MELANENCHYTRAEUS SOLIFUGUS

appears. As a whole, these clusters have the aspect of glands, but no
excretory duct could be detected. The aspect of the white and strong
refracting granules leads me to think that they are uric products, and that
the function of these problematic organs is excretory.

The dorsal vessel, or heart, appears on the sections from the 12th segment
towards the head. Its posterior end is therefore neither praeclitellic nor
postclitellic, but intraclitellic. This includes a cardiac body, or cardiac
gland, of irregular shape, made of a small number of cells, in each transverse
section. Having at my disposal only preserved specimens, I could not
observe the colour of the blood ; I was unsuccessful in reconstructing from
the sections the distribution and course of the blood-vessels.

The lymph cells seem to be all of one sort ; I have drawn some in Fig. 14.

The nephridia (Fig. 15) are of irregular shape, with few large nuclei ;
the cells corresponding to these nuclei are not clearly outlined. Nearly
the whole mass of the nephridium is built by the intricate and densely
coiled tube. The wall of the excretory duct is thick and pigmented
as it approaches the external opening. The latter lies on the line of
the ventral bundles of chaetae, in front of the bundle of the segment in
which it opens.

The desticles and ovaries offer no noteworthy peculiarities ; in my speci-
mens the latter were little developed, even in the most mature, in which the
spermatogenesis was rather advanced. This fact indicates a condition of
proterandry.

In the more developed specimens enormous sferm-sacs extend from the
roth to the 15th segment, and fill nearly the whole body-cavity. We find
in them all the stages of spermatogenesis—large spermatogonia, spheric
follicles derived from multiplication of them, and bundles of very minute
zoosperms ; the latter are, however, in small numbers. But in most of the
specimens I did not observe sperm-sacs nor spermathecae ; testicles and
ovaries were very small and the sperm-ducts wanting, their distal part only
being recognisable as a rudiment.

My Fig. 16 gives the reconstruction of the left sferim-duct from a series
of sagittal sections. The funnel (¢) opens in the cavity of the 11th
segment. It gives rise to a somewhat twisting tube, which runs backwards
as far as the 15th segment, where it is tightly coiled; from there it returns
forward to its external opening in the 12th segment. The last tract forms
a spherical bulb (a), but before reaching it the tube presents a fusiform
swelling (c), whose wall is very thick and made of long cells, directed
radially on the transverse section, the lumen being not widened. Bundles
of prostatic (spermiducal) glands (0) are related to the bulb; another little
group of glands (e) lies around the tube, above its fusiform thickening. As
I mentioned above, the 12th segment, in which the sperm-duct opens, is
deficient in ventral bundles of chaetae.

I have given in Fig. 17 a reconstruction of the ssermathecae, made from
a series of transverse sections of the most developed specimen, which I

5

MELANENCHYTRAEUS SOLIFUGUS

examined anatomically. Their external opening lies near the anterior limit
of the 5th segment. A cylindrical duct made of cylindrical cells leads —
from the external opening to a wide cavity, which extends at its base into
closed appendages or diverticula. These are only two larger on the right
side, three smaller on the left. The two spermathecae communicate with
one another, or, more exactly, they form a continuous whole, which traverses
the dorsal portion of the intestine, without opening into the latter.

This anatomical description and the accompanying plate show so many
singular facts in the structure of the worm examined, that I feel justified
in forming for it a new genus, of which it is the only known species. From
its obscure colour and light-shunning habits, I have called it Melanenchytraeus
solifugus. ;

I translate here the diagnosis which I have already published in the ~
Rendiconti della R. Accademia det Lincez.*

Melanenchytraeus, Emery.

Hypoderm pigmented. All the segments with dorsal and ventral
bundles of 4 chaetae each. The latter are slightly sigmoid, longer in the
foremost segments. No ventral bundle in the 12th segment, which bears the
opening of the sperm-duct. The latter is very long, and forms a coiled loop,
extending back to the 15th segment. Above the spherical bulb, which
forms its distal end, it presents a fusiform swelling ; spermiducal glands are
present. The sperm-sacs are ample, extending through several segments.
The spermothecae do not open into the intestine; they are continuous with
one another, and bear at the base of their ampullz two or three diverticles
each. The nephridia are very much convoluted, with few nuclei. The dorsal
vessel begins in the 12th segment, and includes a cardiac gland. A cephalic
pore is present, but no dorsal pores. The epithelium of the pharynx contains
branched pigmented cells. There are no salivary glands, and no distinct limit
separates the cesophagus from the intestine. In segments 4-8 the body
cavity is largely taken up by unicellular glands, which, by means of long and
very thin prolongations, reach the surface of the skin near the ventral bundles
of chaetae.

M. solifugus, Emery.

The largest specimens are a little over one centimetre in length; the
diameter of specimens preserved in spirits and moistened in water is about
one-third of a millimetre. The body is cylindrical, tapering imperceptibly
towards the hindmost extremity. The cephalic lobe is rounded. I counted
53 segments in one specimen. Colour dark brown, nearly black.

The sigmoid chaetae, the cardiac body, and the much convoluted nephridia
assign to Melanenchytraeus a position near Mesenchytraeus. It differs from
the latter chiefly by the long and complicated sperm-duct. The dark
colouring of the hypoderm and other organs has not been observed in any
other member of the Enchytraeide.

1 Vol. VII., 1° sem., ser. 5. Seduta del 6 marzo, 1898, p. 110.
6

: fi 1 7
ACID pp

tie
; 5 .
+
il
Z
tr

De invari e Wed (nit ATIETICITIC
MELANENCHY!IRAEUS SULIT OY

MELANENCHYTRAEUS SOLIFUGUS

EXPLANATION OF THE PLATE.

Letters common to all figures.

ca dorsal chaetae. ml longitudinal muscles.

cv ventral chaetae. mé transversal muscles.

ce brain. mé nephridium.

cu cuticle. mv ventral ganglion chain.
A hypoderm. o mouth.

Z intestine. ph pharynx.

zm funnel. : pn nephridial pore.

Zc cephalic lobe. sé septum.

FIG.
FIG.

FIG.

FIG.

FIG.

FI.

EIG;
FIG.

EG:
FIG.
inves

FIG.

FIG

FIG

Roman numerals indicate the order of the segments.

1.—WMelanenchytraeus solifugus ; magnified 9 : I.

2.—Brain and cesophageal ring; reconstructed from a series of
horizontal sections. In front of the brain the cephalic
lobe shows a thickened hypoderm, with pigmented sense
cellsee 130) ca 1.

3.—Sagittal section of the foremost part of the body (combined
from a series of not perfectly sagittal sections), fc cephalic
pore, v blood-vessel. 130: 1.

4.—System of muscular bundles, which move the pharynx (m, ph) ;
reconstruction ; the outer wall of the body is supposed
to be transparent. Of internal organs, the central nerve
system and the intestines only are drawn. 100: I.

5.—Section of the intestinal wall in the fore part of the body,
with the chloragogene cells, ch/; ez ciliated intestinal
epithelium, s blood lacunes. 380 : I.

6.—Section of the epithelium of the pharynx; between the
epithelial cells there are branched pigment cells. 380: 1.

7.—Transverse section of the body wall. 380 : 1.

8.—Section of the body wall in the clitellar segment; from a
specimen approaching maturity. 360 : I.

9.—Horizontal section of the cephalic lobe: cs sense cells.
Z8O jie

10.—The four chaetae of a bundle in a posterior segment, isolated by
means of caustic potash. 380 : I.

11.—Longitudinal vertical section of the 6th segment, showing the
body cavity filled by unicellular glands gZ, 250: 1.

12.—Longitudinal vertical section of the 1oth segment, showing
the cluster of granulated cells, x, and the large dark
pigmented cells, fg, which lie around the bundles of
ehactacwe 25On- i.

13.—Longitudinal section through the ventral bundle of chaetae
in a posterior segment. 250 : I. ‘

14.—Three lymph cells in the coelome. 380: 1.

7

MELANENCHYTRAEUS SOLIFUGUS

Fic. 15.—The right nephridium of the. 15th segment, with the neigh- {
bouring bundles of chaetae. Combined figure | from two _
sections, 250 : I. ¢
Fic. 16.—Reconstructed sperm-duct of the right side. p pore, a bulb —
(drawn as semi-transparent), in which the prostatic glands
bb open; c¢ fusiform swelling of the duct; d@ loop sur-_
rounded by the glands ¢, zz funnel. 130: I.
Fic. 17.—Reconstructed spermathecae as a transverse section (from “

a series of transverse sections), vs external pore, dvs

duct, vs cavity of the spermathecae, ars its appendaes
130 32k
Fic. 18.—Aoplophrya sp? parasite in the intestine of Melinenchywraae

380 : I. ae

FIG. 19.—Parasitic cysts from the intestine of MWelanenchytraeus ; a entire |
cyst; 4 longitudinally cut cyst, showing its contents of —
nucleate clear globules separated from each other oy a
pigmented matter. "280 [> M1:

Additional Note-—The Italian edition of the above pages was in the
press when I received from Mr. Percy Moore a separate copy of his valuable
paper on the Alaskan Enchytraeid.1_ Mr. Moore had at his disposal many
more specimens than I had, and among them a number of sexually mature
specimens, which allowed him to recognise the ovisacs and female pores.
He found that the spermathecae do communicate with the intestine by a
small pore. I have revised the only series of sections which I possess from a

specimen with apparently fully developed spermathecae, and cannot find any ~ i ‘
pore ; but the organs lie in close contact with the intestinal wall, and it oy of ge

be supposed that my specimen was abnormal or not fully mature.

Mr. Moore describes another smaller species whose spermathecae are i a |
without diverticula, and calls it WZ. nivus. This and I. solifugus he refersto
the genus Mesenchytraeus, regarding the characters of Welanenchytraeus not

sufficient to justify a separate genus.
After the snow was melted on the glacier, Mr. Bryant observed the
worms to become more active, living in little water pools on the glacier. I

suppose that the most mature specimens came from such localities, and that

the eggs are laid in the water. Mr. Moore examined also specimens collected
by Mr. Wright on the Muir Glacier, and identified them with both JZ. solifugus

and zzvus.

BOLOGNA, /uly, 1899.

* A Snow-inhabiting Enchytraeid (Mesenchytraeus solifugus, Emery), collected by Mr.
Henry G. Bryant on the Malaspina Glacier, Alaska, in Proc. Acad. Nat. Sc, Philadelphia,
1899, pp. 125-144, pl. VII.

8

wg