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The Cambridge Manuals of Science and

Literature

EARTHWORMS AND THEIR ALLIES

No, 29.

>

FACULTY OF Forestry
UNIVERSITY of TORONTO

CAMBRIDGE UNIVERSITY PRESS
g#ondon: FETTER LANE, E.C.
C. F. CLAY, MANAGER

Evinburgh: 100, PRINCES STREET
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Bombay and Calcutta: MACMILLAN AND CO., Lro.

All rights reserved

TS (eS
EARTHWORMS AND ‘ADs,
THEIR ALLIES

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BY

FRANK E. BEDDARD
M.A. (Oxon.), F.R.S., F.R.S.E.

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Cambridge :
at the University Press

New York:

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OuBY

Cambringe :
PRINTED BY JOHN CLAY, M.A.
AT THE UNIVERSITY PRESS

With the exception of the coat of arms at
the foot, the design on the title page is a
reproduction of one used by the earliest known
Cambridge printer, John Siberch, 1521

PREFACE

es importance of earthworms in questions relating

to geographical distribution is so universally
admitted that it seemed to me convenient to embody
in a short volume the principal facts.

It became necessary in order to accomplish this
task in an adequate fashion to preface the dis-
tributional facts with some anatomical and zoological
data. I have reduced this section of the book toa
minimum and I trust that the illustrations will enable
the reader, who is not specially acquainted with the
structure of these animals, to obtain an idea of their
general features and variability in external character
and internal anatomy. While the use of technical
terms is inevitable in presenting such details, it
will be found, I think, that a reference to the
figures will render them intelligible.

vi PREFACE

Since this volume mainly deals with the pheno-
mena of distribution, I have included in my survey
nearly all of the usually admitted genera of worms,
particularly of the terrestrial forms, which are in the
light of our present knowledge the more important
in considering this subject.

ZOOLOGICAL Society oF LONDON.
December, 1911.

CONTENTS

Structural and Systematic
Mode of Life .

The external features of Earthworms and their

relation to habit and environment .
Sense Organs and Senses of Earthworms

Relative frequency of Earthworms in different
regions of the World

Peregrine forms
The Earthworms of Oceanic Islands
Movement and Migration among Earthworms

The Geographical Distribution of Earthworms

List of Literature referring to Earthworms

Index A é : z : ‘ “

PAGE

: aha r i ee ts Pee eS ea ce

CHAPTER I
STRUCTURAL AND SYSTEMATIC

THE group of segmented, bristle-bearing, worms,
termed Oligochaeta by zoologists, comprises what are
popularly known as earthworms together with certain
forms, inhabitants of ponds, lakes and rivers, which
are not so well known as to have received a more
distinctive name than merely ‘worms. Their next
allies are apparently the leeches and—a little more
remote—marine bristle-bearing worms termed Poly-
chaeta; the three groups, together with perhaps a
certain number of other forms belonging to smaller
groups, constitute the Annelida which are a distinct
and separate assemblage of invertebrate animals.

The most interesting features about these Oligo-
chaetous worms are their very great anatomical varia-
tion and the facts of their distribution over the globe.
Their importance as geological agents in levelling
the ground was made known a long time ago by
Darwin, and that aspect of earthworms has remained
in much the same position as Darwin left it. We
shall concern ourselves here only with the structure,

B. E. 1

2 EARTHWORMS AND THEIR ALLIES § [cn.

habits, and range of the earthworms and their im-
mediate allies, the aquatic Oligochaeta. These three
aspects of the animals dovetail into each other more
thoroughly than is the case with some other groups.
This is due to the fact that they have of late years
been very thoroughly studied from the anatomical
and distributional side. So lately as 1889, M. Vaillant
in a very comprehensive treatise was only able to
enumerate 369 species, of which a large number
were but incompletely differentiated, and some are
no longer admitted. There are at the moment of
writing perhaps 1500 species, the vast majority of
which are well known owing to careful investigation.
Furthermore there are but few parts of the world,
and these are not of large area, from which earth-
worms at any rate have not been gathered. Though
there can be no doubt that a very considerable number
of species await discovery, it would seem that we are
in possession of information which is not likely to be
seriously affected by future researches.

THE ANATOMY OF EARTHWORMS.

Although it is not contemplated to make the
present volume a guide to the structure of this
group of worms, it is necessary to give some little
anatomical sketch of the group in order first of all
to illustrate their diversity of structure, secondly to

T] STRUCTURAL AND SYSTEMATIC 3

give reasons for the classification of them,
and thirdly to enable the reader to realise
certain structural details which it is abso-
lutely necessary to give some account of in
order to explain other matters.

It is for example impossible to attempt
any account of the fitness of some of these
animals for their terrestrial life and of
others for an aquatic life without treating
of anatomy to some extent.

I shall take one particular species as a
type and indicate later the principal diver-
gencies shown by other forms. According
to the general opinion among those who have
studied the Oligochaeta I take as a repre-
sentative form a Megascolecid (this and the
other families are dealt with serzatim on
p. 14 et seq.), as this group is presumed to
be the oldest, and within that group a
representative of the genus Notiodrilus
which is with some reason held to be the
most primitive genus in the group. Finally
[have no particular reason for selecting the
species Notiodrilus tamajusi except that
there happens to be a longer and fuller
description of it than of many.

ALTERS

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F

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NH

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HAAANAAANIASVUNDLEUATOEOTAATDSUSYNHOODSROGADAURARDIOALASHY

Fi

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Fig. 1. Notiodrilus tamajusi. The worm shown from the ventral
surface. About natural size. (After Eisen.)

1—2

4 EARTHWORMS AND THEIR ALLIES [cu.

This earthworm is a native of Guatemala and is
some six inches in length with a diameter of perhaps
a quarter of aninch. The front part of the body is
thicker than posteriorly. The body will be seen to
be divided into some 218 rings by circular furrows
which run right round the body. These divisions are

Fig. 2. Fig. 3.

Fig. 2. The same species; first two segments and prostomium shown
from ventral surface, I prostomium, II first segment without any
setae, III second segment with its four pairs of setae (the dorsal-
most seta of each outer pair is not visible in this view).

Fig. 3. A section through the body of the same species showing the
ventral position of the pairs of setae. (After Hisen.)

termed segments or somites. At the head the mouth
is surrounded by the first of these, and on the dorsal
surface of that segment is a projection like an in-
complete segment which is known as the prostomium.
From the xuith segment to the middle of the xxth
the body has a different appearance, and this region is

T| STRUCTURAL AND SYSTEMATIC 5

known as the clitellum. Each of the 218 segments
of the body except the first, and possibly one or two
at the hinder end, is furnished with eight minute
projecting bristles, the setae ; these are disposed in
pairs and all lie upon the ventral aspect of the worm.
The movement of these by special muscles aids in
locomotion.

An examination with even a hand lens shows a
number of external pores which are important.
Anteriorly there is the mouth which is overhung
by the prostomium referred to above. At the
extreme hind end—and surrounded by the last
segment of the body—is the vent. Along the middle
line of the back are a series of pores, one just at the
very anterior edge of each segment, through which,
when the worm is dried and then slightly pressed,
liquid is seen to be ejected. These are called the
dorsal pores and they belong one to each segment
with the exception of the first seven, or—in some
cases—more, segments. In front of one or other of
the pair of setae which is situated most laterally,
z.e. furthest from the ventral median line, is an orifice
on each side in all but the first one or two segments
of the body. These paired pores are the external
outlets of the excretory organs frequently termed on
account of their regular repetition with the segments
‘segmental organs, but more conveniently to be
named nephridia. In the clitellar region and in fact

6 EARTHWORMS AND THEIR ALLIES [cu.

on each of the segments XVI, XVIII, XIX are a pair
of pores of which those on the xviith segment are
the least conspicuous. The large pair of pores on
each of segments Xvi and xIx occupy the position
of the ventralmost pair of setae, which are here
absent, or rather replaced by a very long curved and
ornamented seta, which projects out of the orifice.
These two pairs of pores are the outlets of the
prostatic glands as they have been termed. The

Fig. 4. The same species. Ventral view of segments xvI-xx
(numbered in the figure) which form the clitellum, the posterior
boundary of which is shown by a curved line on segment xx.
The figure will be understood from the annexed description.

minute pair of pores on segment xvi do not take
up the position of the ventral setae ; for these are
present and to the inside of each pore. A groove,
shaped something like a reversed 3 or the Greek letter
>, connects the orifices of each side of the body, the
middle part of the groove, where the two semicircular
halves of which it is composed meet, coinciding with
the minute pores on segment xviI which are the
orifices of the sperm ducts.

1] STRUCTURAL AND SYSTEMATIC 7

On segment XIV are a pair of very minute pores
a little in front of the ventralmost setae and thus
very near together. These are the openings of the
oviducts. Finally, near to the anterior border-line
of segments vili and Ix and on a line with the
ventral pair of setae is a pore on each side through
which the cavity of the spermathecae reaches the
exterior.

So much then for the external characters of our
worm. We next turn to the internal anatomy. When
the worm is opened by a longitudinal section from
end to end, and the two flaps of skin are turned
outwards and pinned down, the internal structure is
almost completely revealed. Running from end to
end is seen the alimentary canal; the general cavity
of the body (coelom) in which it lies, as do of course
the other organs to be enumerated, is seen to be
divided by cross divisions, the intersegmental septa,
into a series of chambers which correspond with the
external division into segments. The septa are in
fact inserted on to the body-wall along the furrows
which mark the divisions between adjacent segments.
Anteriorly the large pharynx is responsible for con-
fusing the arrangement of the septa, which become
subdivided and fused or are prolonged a greater way
backwards and thus present a less obviously segmental
disposition. Certain of the more anteriorly placed of
these septa are much thicker than the rest. This is

8 EARTHWORMS AND THEIR ALLIES [cH.

the case with the septa which separate segments V to
xu. The alimentary canal is perfectly straight and
runs in the middle line, being supported by the septa
which it perforates. The mouth leads into a buccal
cavity which later becomes the pharynx, a portion of
the tube which is much thickened by muscular walls
dorsally. Then follows a very short section of the
oesophagus and in the fifth segment this becomes
the gizzard, a very characteristic organ with thick
muscular walls quite smooth and with a very thick
lining of structureless membrane. After this is a
narrower tube, the rest of the oesophagus. Into this
open in each of segments VII, VIII, IX a pair of cal-
ciferous glands ; these are diverticula of the gut with
much folded walls, the cells of which secrete carbonate
of lime. In the xuth segment or so, the oesophagus
suddenly widens out to form the intestine which runs
as such to the end of the body. This wider tube has
a ridge running along its dorsal side, the typhlosole.
Along the dorsal surface of the intestine and the oeso-
phagus is seen a red tube, contractile during the life
of the worm, which is the dorsal blood vessel and
whose contained blood is coloured red, as is the blood
of vertebrated animals, by haemoglobin. But in the
earthworm the colouring matter is not situated in
corpuscles as in the vertebrate. The dorsal vessel is
connected by a few pairs of equally contractile trans-
verse trunks with a ventral vessel which is not

1] STRUCTURAL AND SYSTEMATIC 9

Fig. 5. A longitudinal section
through the middle of the first
nineteen segments of the body
of Notiodrilus vasliti (a species
very closely allied to that
described in the text), the seg-
ments are numbered 1, 11, &.
D.v. dorsal blood vessel, G
gizzard, H hearts, @ oeso-
phagus lying in front of
gizzard behind which another
tract of still narrow oeso-
phagus is seen opening into
Int. intestine. The whole
alimentary canal is supported
by the intersegmental septa
(Pr.c.) between which is the
system of spaces forming the
coelom, ov.d. pore of oviduct,
Splh. orifices of spermathecae,
3 orifice of sperm duct, o
ovary, ¢ spermaries. (After
Eisen.)

rey

NCS

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un,
“ene

PRLS 2

ithe, Se
onuent at

eRA Recast Wis (11/1 ELAR

10 EARTHWORMS AND THEIR ALLIES [cu.1

contractile. There are other branches of these main
longitudinal trunks and some minor longitudinal
trunks which we shall not stop to describe further.
The nervous system of the worm consists of a pair of
ganglia which lie above the gut in the third segment ;
they are connected by a commissure running round
the gut with a chain of closely fused pairs of ganglia,
one for each segment to the very end of the body.
In each of the segments, except the first two or three,
there are a pair of excretory organs known as
nephridia; these are essentially coiled glandular
tubes opening on to the exterior by the regularly
placed pores already referred to in considering the
external characters. The tube ends in a funnel-
shaped, and therefore dilated, mouth, which opens
into the segment in front of that which contains the
rest of the organ; a nephridium therefore lies in two
segments. The only other important organs which
are left for consideration are those devoted to the
reproduction of the species. The essential organs are
the spermaries and the ovaries. Of the former there
are two pairs of minute whitish bodies which lie in
segments X and XI on either side of the nerve cord
attached to the anterior septal wall of their segments.
The ovaries are not in the following, but in the x1uth,
segment, and occupy an identical position in that
segment. <A short tube with a funnel or trumpet-
shaped and wide orifice opens into the cavity of the

Fig. 6. Genital region of Maoridrilus dissimilis (in which species the different

organs are essentially as in Notiodrilus tamajusi). The oesophagus is cut
away between the xth and xviiith segments to display the various organs. 7
external orifices of nephridia which alternate in different segments; the one
lettered opens in front of dorsalmost pair of setae, that of segment xvi opens in
front of ventralmost pair, p coiled glands opening on to xvith and xrxth
segments, sc. sacs containing long seta, associated with these glands, t spermary
of segment ; another pair in an exactly similar position in segment x1. Behind
spermaries are funnel-shaped openings of sperm ducts which are seen running
along the body to their external orifice on xv1iith segment. v.s. sperm sacs
behind the posterior of these and in segment x1ir is seen the large ovary
corresponding in position to the spermary and opposite to each ovary the
oviduct. (x 3.)

12 EARTHWORMS AND THEIR ALLIES [cH.

xuth segment opposite to each, and, perforating the
septum, opens on to the exterior on the xIvth segment.
Asimilar but larger and more folded pair of trumpet-
shaped funnels opens in the same way opposite to
each spermary. But in this case the two tubes of the

Fig. 7. A spermatheca of Notiodrilus tamajusi. The external
orifice is shown at 0; above this are the diverticula, s is a portion
of an intersegmental septum. (After Hisen.)

sperm ducts run backwards for some way and those

of each side after joining open on to the xvith

segment by the pores already mentioned. On the

Xvuth and x1xth segments open two glands which

are long and tubular in form and much coiled. These

are the spermiducal glands and each opens in common

1] STRUCTURAL AND SYSTEMATIC 13

with a muscular sac containing the long and orna-
mented seta referred to in describing the various
external orifices. It will be noticed that the sperm
duct has no direct connection with these glands but
only indirectly through the external gutter which
connects the three male orifices of each side of the
body. Segments 1Ix—xiI inclusive contain certain
sacs which depend from, and are formed as out-
growths of, the septa of those segments. These are
the sperm sacs in which the male germ cells undergo
their development. A corresponding body (but very
much smaller) is sometimes found in relation to the
ovary but has not been actually described in the
particular species dealt with here. Finally, in segments
vill and IX are a pair (that is four altogether) of
roundish sacs, with two or three minute diverticula,
known as the spermathecae. In the diverticula of
these sacs are stored the sperm derived from another
individual.

This completes the general sketch of the structure
of Notiodrilus tamajusi which we have selected as a
type. In this same genus are a large number of species
which differ from that selected in various small
structural points. Thus in N. annectens (Beddard), a
species from New Zealand, the spermaries and ovaries
are attached to the posterior, instead of to the anterior,
wall of their segments, and there are neither calciferous
glands nor modified setae upon segments XVII and XIX.

14 KARTHWORMS AND THEIR ALLIES [ca.

In all essentials however the two types agree and
are thus to be looked upon as referable to the same
genus. Starting from the structure of these types we
may now sketch in quite a brief way the main
divergencies of structure shown in the group of
Oligochaeta.

We shall naturally begin with the family Megasco-
lecidae of which a type has just been described.

Within the limits of the same sub-family as that
which contains Notiodrilus, z.e. the Acanthodrilinae,
the changes of structure affect all the principal organs
of the body except the nervous system, but are not
very large and vary from genus to genus. They are
mainly perhaps in the direction of reduction and
simplification. Thus in Chilota, Maheina and Ya-
gansia the spermaries are reduced to one pair in
either the xth or xith segment, while in Yagansia
one pair of spermathecae and of spermiducal glands
have also disappeared. In Microscolex the sper-
maries remain normal, but one pair of spermathecae
and of spermiducal glands have disappeared, the
remaining organs of these series being in the 1xth
and xviith segments respectively. In Microscolex,
Chilota and Yagansia, moreover, there is a further
degeneration in the disappearance of the calciferous
glands. These glands are often absent and sometimes
less developed in the New Zealand Maoridrilus,
which is otherwise not a degenerate form and differs

1] STRUCTURAL AND SYSTEMATIC 15

characteristically from Notiodrilus by the fact that
the paired nephridia alternate in position in successive
segments, being now in front of the dorsal, and in
other segments in front of the ventral, pairs of setae.
While these genera are somewhat degenerate, the
New Zealand Plagiochaeta has undergone specialisa-
tion in an upward direction. For the setae of each
segment are increased to a large number much ex-
ceeding eight.

It is not a long step to the sub-families Diplocar-
diinae and Trigastrinae. In the first of these, an
American race confined to the northern and central
parts of that continent, the male pore shows a
tendency to move backwards, being situated on any
of segments XVIII-xxI. The two spermiducal glands
follow it, but are always placed one pair in front
and one behind, as in Notiodrilus. In this group we
get a new feature of specialisation in the duplication
or triplication of the gizzard.

So too with the Trigastrinae where there are
either two or three gizzards ; but in this sub-family
another modification has become apparent. The
paired nephridia have disappeared and their place
is taken by several, often quite numerous, pairs of
much smaller nephridia called on that account ‘mi-
cronephridia’ instead of ‘meganephridia. To this
sub-family belong the especially African but also
American and Malayan Dichogaster, whose name is

16 EKARTHWORMS AND THEIR ALLIES [ca.

derived from the important fact that it possesses two
gizzards.

Not far off is to be placed another sub-family,
that of the Octochaetinae, which is New Zealand
and Indian in range, the intermediate countries being,
strange to say, not populated by this race of Oligo-
chaeta. The group contains several genera of which
Octochaetus, Eutyphoeus, and Dinodrilus are the
best known. All these worms agree in the main
features of their anatomy with Notiodrilus ; but they
have diverged in different directions. Thus in Octo-
chaetus the typical two pairs of gonads and glands
belonging to the generative system have been
retained, while the nephridial system consists of
micronephridia ; in Hutyphoeus, one pair of spermi-
ducal glands has disappeared, and as a general rule
the species of this genus have only one pair of
spermaries and the corresponding pair of sperm ducts.
They are close to Octochaetus. The third genus
mentioned, Dinodrilus, is a New Zealand form
specialised in possessing 12 setae in each segment.
Otherwise it is not far removed from Octochaetus.

A fifth sub-family is also easily referable to the
type whose structure has been dealt with as a pre-
liminary to the present survey. That sub-family is
the Ocnerodrilinae which is American and African
in range. These worms are somewhat degenerate
in comparison with their allies. Thus the calciferous

1

STRUCTURAL AND SYSTEMATIC 17

Fig. 8. Ventral view of Eutyphoeus masoni. p papillae, ¢ male
pores, ? oviduct pores. (x3.)

18 EARTHWORMS AND THEIR ALLIES [cu.

glands are reduced to a single pair or to a single
gland in the 1xth segment, the nephridia though
regular and paired have no covering plexus of
blood vessels, and the worms themselves are slender
and delicate, being indeed often aquatic in habit.
The spermiducal glands, which are as in the former
sub-families independent of the sperm ducts though
sometimes opening in common with them into a short
pocket-like ingrowth of the skin, are reduced in their
minute structure and much simpler than in the other
types.

The genus Kerria is the least reduced perhaps.
It has the male pores on segment Xvi with a pair
of spermiducal glands on the segments preceding
and following this in the typical Acanthodriline
fashion. There are two pairs of spermathecae in VII
and 1x, but the spermaries are reduced to one pair
in xX. The gizzard is present. Ocnerodrilus is a
little further reduced from this last. The gizzard
has gone ; there is but one pair of spermiducal glands
(as a rule) opening in common with the extremity of
the male duct on to segment xvii; the spermathecae
also are reduced to one pair, but there are two pairs
of spermaries. The African Nannodrilus is more
robustly built. There are two gizzards, the male
duct opens into a muscular pouch, into which also
open one of the two or three pairs of spermiducal
glands. There are two or three other genera and

1] STRUCTURAL AND SYSTEMATIC 19

sub-genera not showing any great divergencies from
the range of structure indicated in briefly defining
those enumerated above.

Finally, we have the largest of all the sub-families
of this family, viz. that of the Megascolecinae. These
worms are mainly tropical in range and also mainly
found in the Indo-Australian portion of the world.
In them the sperm ducts open in common with
the usually single pair of spermiducal glands and
prevalently upon the xvinth segment. The glands
moreover have not always, though they often have,
the tubular form shown in all the sub-families hither-
to considered. In many forms they are branched
and lobate glands, and if there are two pairs one may
be of one type and the other of the second and
derived type, as for instance in Megascolex ceylonicus.
Furthermore, it is much commoner among the genera
of this sub-family for the setae to become numerous
and to spread right round the segment; this con-
dition is seen in the genera Pheretima, Megascolex,
Diporochaeta, Perionyx, Plionogaster. The sper-
mathecae also are commonly more than the typical
two pairs of the forms already considered, and in
certain species (for example Pheretima hexatheca)
there are as many as six pairs of those organs which
are moreover—and in this they resemble the majority
of species of the last sub-families—nearly always
furnished with a diverticulum or diverticula. The

2—2

20 EARTHWORMS AND THEIR ALLIES [cu.

nephridia are either paired or numerous and these
various characters allow of the sub-family being split
up into sixteen genera or thereabouts.

As an example of another type of organisation
and as contrasting with Notiodrilus we may now
briefly describe the structure of the genus Ponto-
scolex (better known as Urochaeta), a member of the
American and African family Geoscolecidae.

The worm is some four inches long and composed
of as many as 212 segments. Each of these except
the first has eight setae which for the first few
segments of their occurrence are disposed in four
pairs in the usual fashion. Behind this point how-
ever the setae cease to present this symmetrical
arrangement and are irregularly disposed so that a
given seta is not in the same line with the corre-
sponding seta of the segments in front or behind.
There is thus no region of the body which has
not a seta implanted upon it; and the effect is
therefore comparable to the condition obtaining in
those worms, such as Pheretima, where circles of
numerous setae are met with. There are however
only eight ina given segment. The clitellum extends
from segment XV to XXII or XXIII and is developed
only dorsally and laterally. It has setae like the rest
of the body ; but those upon the clitellum are longer
and more markedly ornamented than are those of the
body generally. The latter are not only sculptured

1| STRUCTURAL AND SYSTEMATIC 21

with fine ridges but are bifid at their free extremity.
The prostomium is often apparently completely
absent. It is however really present but is retractile.
As to the pores which are visible externally the
dorsal pores are completely absent. The pores of the
nephridia lie in front of the dorsal pair of setae or in
a line corresponding to the position of those setae
where the arrangement has become irregular. The
spermathecal pores are three pairs and are in the
very front of segments VII, VII, 1x. The male
pores, very inconspicuous, lie on the ventral side of
segment XXI just within the clitellum. The oviducal
pores are on segment XIV.

As to internal anatomy the general plan of the
segmentation shows no great differences. Certain
septa only show a difference, @.e. those separating
segments VI-xI which are specially thickened. In
the alimentary canal a gizzard in segment VI is to be
noted and three pairs of calciferous glands in segments
vil-Ix. The nephridia are paired structures and
commence early. The first two or three segments
are occupied by a pair of large glands opening into
the buccal cavity which are apparently a slightly
modified pair of nephridia and are generally termed
‘peptonephridia’ since they are associated, as_ it
would appear, with the function of alimentation and
are not purely excretory organs. There is but a
single pair of spermaries in segment XI, and of

22 KARTHWORMS AND THEIR ALLIES [cua.

ovaries in segment xm. The sperm ducts open on
to the exterior in the position already mentioned and
they are not associated at their pore with any glands
comparable to spermiducal glands. A pair of sperm
sacs depend from segment XI and traverse a consider-
able number of segments, being thus long and
tongue-shaped instead of short and limited to one
segment. The spermathecae are three pairs of
elongated sacs in segments VII-Ix, without any
diverticula at all.

It will appear therefore that many and consider-
able differences divide Pontoscolex from Notiodrilus
and indeed from all of the Megascolecidae whose
structure has been touched upon in the foregoing
pages. The most important of these are the orna-
mented setae and their arrangement and the modi-
fication of the setae upon the clitellum: the absence
of diverticula to the spermathecae: the absence of
terminal glands associated with the male ducts.
Although taken in their entirety these characters are
distinctive of the American Geoscolecidae (sub-family
Geoscolecinae), there is no one of them which is not
to be found in some Megascolecid. Thus the sub-
genus Ilyogenia (of Ocnerodrilus) has sometimes no
spermiducal glands: the genus Perionyx has sperma-
thecae without diverticula in some species, and other
genera of Megascolecinae are in a like condition.
The setae of Dichogaster are sometimes ornamented,

1] STRUCTURAL AND SYSTEMATIC 23

while in Pheretima houlleti the clitellar setae are
different from those upon the other segments.

We can in fact only define the family Geoscole-
cidae by an assemblage of characters which are
mainly these: dorsal pores absent, only a few in
the neck region being occasionally present ; setae
generally ornamented, those of the clitellum being
larger and more marked than the others; sperma-
thecae without diverticula; often instead of a pair of
those pouches in the segment a large number of very
small sacs, as in Microchaeta, Kynotus. Sperm
ducts without terminal glandular or muscular sac,
except in a few cases; setae always eight in a
segment except in the genus Periscolex which has
acquired the ‘ perichaetous’ condition. The range of
variation shown in the anatomy of the Geoscolecidae
will be best taken in connection with the several
sub-families into which it has been subdivided. In the
first of these, the Geoscolecinae, no great differences
divide the genera from that selected as the type, viz.
Pontoscolex. The long sperm sacs attain to an
extraordinary length in Tvichochaeta (or Hespero-
scolex) where the single pair extends through no less
than 109 segments. Though as a general rule the
sperm ducts open directly on to the exterior they do
so through the intermediary of a large pouch in
Glossoscolex (= Titanus). In Onychochaeta the setae
on the last segments of the body are very much

24 EARTHWORMS AND THEIR ALLIES [cu.

enlarged and thus form a more effective means of
holding on to the soil than is possessed by other
species. :

The sub-family Hormogastrinae which contains
but a single genus Hormogaster is remarkable for
being limited in range to the Mediterranean coasts.
The genus is mainly distinguished by possessing three
gizzards; otherwise it is not very different from the
sub-family just described. The African and Mada-
gascar forms are associated (together with a few
Asiatic forms) into a third sub-family Microchaetinae.
These worms frequently possess a_ considerable
number of very small spermathecae in segments
XII, X11 or thereabouts instead of the usual paired
arrangement. They have too very often glands con-
nected with the enlarged setae already mentioned
which are however (in the genus Kynotus at any
rate) usually in front of the clitellum. The latter
organ, contrary to what we find among the Geos-
colecinae, is often behind the point of orifice of the
male pores. This is so with Kynotus.

The last sub-family, Criodrilinae, has but three
genera Criodrilus, Sparganophilus and Alma. These
worms do not show any very marked differences from
other Geoscolecids. Alma is noteworthy for the facts
that the male pores are borne upon long processes of
the body which bear specially modified setae and
that one species at any rate has gills.

1] STRUCTURAL AND SYSTEMATIC 25

Another type of structure is offered by the
Eudrilid earthworms which form rather a restricted
family. These worms are as a rule quite easy to

4
:

(OTE,
EE

a4

Fig. 9. Ventral view of Polytoreutus Kilindinensis, head end (x 2).
p papillae, ¢ male pore, ? female pore.

distinguish by their external characters only. For
the apertures of the spermathecae and sperm ducts

26 EARTHWORMS AND THEIR ALLIES [ca.

are apt to be very large and conspicuous. They are
also generally unpaired, a character which is however
not confined to the Eudrilidae ; for there are Mega-

Fig. 10. Ventral view of Polytoreutus finni, head end ( x 2),
lettering as in fig. 9. °
scolecids, such as Fletcherodrilus, and Geoscolecids
in which the same unpaired character occurs. The
principal feature of the family is that the ovaries are

1] STRUCTURAL AND SYSTEMATIC 27

commonly enclosed in sacs—comparable to the sperm -
sacs which frequently envelop the spermaries in other

1
Sperm SAGE 12
Sperm auct. _- te
ovary----~-
EOOSAC 2:5 Spermalotheca
. 14
Ovzductl-- --
1S
16
4
P18
Atriwin
Fig. 11.

Organs of reproduction of Hudriloides durbanensis.

earthworms—and-that these sacs not only contain the
mouths of the oviducts but are directly continuous

28 EARTHWORMS AND THEIR ALLIES [cH.

with the single or double spermatheca. This is
usually a large sac, always single or consisting of one
pair only, which opens on to the exterior close to the
oviducal pores; these spermathecae in the Eudrilidae
are not comparable to the spermathecae of other
earthworms; for they are in a way comparable to the
sperm sacs, being formed as outgrowths of the septa.
There is some variation of structure within the family.
In a number which are associated into a sub-family
Eudrilacea there are two paired calciferous glands
and a single unpaired one, while the paired nephridia
open by a large pore on to the exterior. In a
parallel sub-family, the Pareudrilacea, the calciferous
glands are apt to be more numerous and have a
totally different structure : they have been apparently
converted into non-digestive glands bearing some
relation to the vascular system. The nephridia
moreover do not open on to the exterior by single
pores, but form a network within the thickness of the
body wall and then open by numerous pores. There
is however no resemblance here to the micronephridia
of Dichogaster and other Megascolecids. In Libyo-
drilus (as an example of the Pareudrilacea) each
nephridium forms a network out of the duct leading
to the exterior. In the interior of the body a series
of paired meganephridia are visible.

The earthworms of Europe belonging to the family
Lumbricidae offer again a rather different type of

1] STRUCTURAL AND SYSTEMATIC 29

structure, which is more reminiscent of the Geoscole-
cidae than of the Megascolecidae or Eudrilidae. In
this family there are no glands appended to, or in
the neighbourhood of, the orifices of the sperm ducts,
such as are found in the other forms. As in the
Geoscolecidae the clitellum is furnished with setae
somewhat different in form from those which deck
the body generally. These setae are never more than
eight in a segment. Dorsal pores (absent in Geosco-
lecidae and in Eudrilidae) are invariably present.
The spermathecae are without appendices and nearly
always simply paired, though rarely we get numerous
much smaller spermathecae in a single segment, as
in Kynotus among the Microchaetine Geoscolecids.
Internally the most striking feature of this family is
to be seen in the position of the gizzard at the end of
the oesophagus and at the beginning of intestine. The
apertures of the male pores are—save for two or three
exceptions where they are further forward—invariably
upon the fifteenth segment, and the clitellum, often
very long, usually begins behind this point, features
which are also seen in Kynotus.

Finally we have the Moniligastridae which differ
from all the types hitherto considered in a few rather
important particulars. These worms are named on
account of the fact that they possess several gizzards
upon the oesophagus, a character which is however
met with in the Megascolecid genus Plionogaster

30 EARTHWORMS AND THEIR ALLIES [ca.

and in certain Eudrilids, eg. Hyperiodrilus. The
main peculiarity of the family is that the sperm
ducts are very short and open on to the next segment
to that which contains the spermaries, as in the
water-living Oligochaeta generally. The terminal
sac into which the male ducts open is moreover
rather like that of such a family as the Lumbriculidae.

THE AQUATIC FAMILIES OF OLIGOCHAETA.

It would seem to be quite possible that when the
fresh waters of the world have been as well examined
for Oligochaeta as have so many parts of the land
areas, the number of purely aquatic Oligochaeta
will be found to equal those inhabiting the land. In
any case we are quite justified at the present moment
in stating that there are rather more families of
these smaller Oligochaeta than there are of the bulkier
terrestrial forms. But while there are certainly
seven or eight distinct families, these do not between
them contain at present so many genera as do the
fewer families of earthworms; and the number of
species of the latter that are known to science
enormously exceeds that of the ‘Limicolae’ as the
fresh-water worms were at one time called in common,
The fact that there are purely marine forms of these
water worms was hardly appreciated at the time that
the term Limicolae was used; now however we are

1| STRUCTURAL AND SYSTEMATIC 31

acquainted with a few such forms, and even with
some which live at will in either fresh, salt, or
brackish water. Of these something will be said later.

These forms have also been collectively treated of
as Microdrili, a term which expresses the undoubted
fact that they are all of small size and sometimes
even minute; others however reach the dimensions
of the smaller species of earthworms. There are a
certain number of characters shared by the various
families which may be considered first of all, before
dividing them into their several subdivisions. These
aquatic Oligochaetes are usually tender and trans-
parent, the muscular layers of the body wall being
much reduced as compared with the tougher terrestrial
forms. The clitellum is also thinner and consists of
a single layer of cells only, thus contrasting with
the double layered clitellum of earthworms. As a
rule the alimentary tract is simplified, there being
no gizzard or glandular appendices of the oesophagus
comparable to the calciferous glands of most earth-
worms. But this rule is not without exceptions; for
we find in Haplotaxis a gizzard occasionally de-
veloped, and in the remarkable genus Agriodrilus
from the Baikal lake a continuous gizzard formation
along the oesophagus, while the Enchytraeidae may
show something very like calciferous glands: and
even a Tubificid, called by Pierantoni Limnodriloides,
has a pair of diverticula of the gut.

32. EARTHWORMS AND THEIR ALLIES [cu.

Other internal organs show certain points of
likeness in all or in the great majority of the aquatic
families. Thus the nephridia are without a plexus
of blood capillaries surrounding them, a state of
affairs which also occurs in some of the slender
Ocnerodrilinae among the earthworms. These paired
organs also are very frequently notfound inthe anterior
segments of the body and these include also as a
general rule the segments in which the reproductive
elements are formed. Save for an exceptional case
among the genera of Enchytraeidae the dorsal pores
are not found among the Limicolae, but in some cases
at least a single pore, the head pore, is found. The
sperm ducts, which among earthworms usually (and
indeed always save in the anomalous Moniligastridae)
traverse a considerable number of segments on their
way from the internal opening into the body-cavity
to the external pore, do not show the same pheno-
menon among the Limicolous Oligochaeta. They are
sometimes indeed limited to a single segment, that
is to say the funnels and the external pore lie in one
segment. In other cases they open on to the exterior
in the segment next to that which bears the funnel,
and it is only rarely that they traverse more than
one segment. There are also points of difference of
general applicability to be noted in the sperm sacs
and egg sacs. The latter are large and extensive,
which is not the case among earthworms, and the

1] STRUCTURAL AND SYSTEMATIC 33

former are as a rule more extensive in the number
of segments that they occupy than among the terres-
trial forms. Another difference which they show is
that their cavity is quite simple and not divided up
by trabeculae into numerous intercommunicating
chambers as in the earthworms. Finally the eggs
of the aquatic Oligochaeta are large and full of yolk
and thus contrast with the very small ova of the
earthworms which are moreover much more abundant.
These features are either of general or universal
occurrence and together form an assemblage of
characters which mark out the aquatic families of
Oligochaeta from their, at least mainly, terrestrial
allies.

We may also refer to certain structures which
although not universal among these aquatic families
are nevertheless found only in them—that is, are not
found in any family of the terrestrial worms of this
order. The most salient of such characters are the
long and hair-shaped setae tapering to a fine point and
often provided with a series of delicate branches like
a feather; such setae are often of very great length
and they occur in their various modifications among
the Aeolosomatidae, Naididae, and Tubificidae. It
is clear that these delicate setae, though they may
not be due in any way to the aquatic life, are rendered
possible by it. To drag such tender processes through
stiff clay would surely break and tear them out. It

B. E. 3

34 EARTHWORMS AND THEIR ALLIES [cu.

may be also mentioned that among the aquatic
families as a rule the intersegmental septa do not
show that thickening in some of the anterior segments
of the body which is so general a feature of the land-
dwelling species. Finally it is only among the aquatic
forms, and among them only in the families Aeolo-
somatidae and Naididae, that asexual reproduction
by budding takes place. Indeed so common and
usual is it in the genera of these families that even
yet there are considerable lacunae in our knowledge
of the organs of reproduction in the said families.

Together with these general similarities are many
points of structural difference among the worms
inhabiting ponds, lakes, and rivers, which allow of
their being divided into a number of quite distinct
families.

One of the most distinct of these families and
lying in any case quite at the base of the series is
the family Aeolosomatidae which includes a number
of distinct species of delicate and transparent
worms, and in whose integument are embedded
round cells bearing a large brightly coloured oil drop;
this is reddish or green in colour, or—and this more
rarely—colourless, but still recognisable as an oil drop.
The green sometimes even verges upon blue on the
one side and yellow on the other, while the red may
approach brown or purple. These worms are assigned
for the most part to the genus Aeolosoma which is

1] STRUCTURAL AND SYSTEMATIC 35

found in all of the great continents and of which
seven or eight species are known. ‘To a more doubt-
ful genus Plewrophleps are assigned a few small
worms which have the general appearance of A eolo-
soma, but are without the coloured or colourless oil
drops in the skin. These worms have a very large
prostomium which is ciliated on the lower surface,
and the body is not markedly segmented externally
by constrictions or internally by septa. The bristles
are slender and hair-like, but among them are in
some species the shorter stouter bristles bifid at the
free tip, which are so general among the aquatic
families of the Oligochaeta. These worms are not
uncommon objects in pools containing weed; and
they are to be found usually crawling among the
weed. They consist as a rule of but few segments
to most of which a pair of nephridia belong. The
ovaries and the spermaries are only known in a few
forms and appear to be unpaired and lie respectively
in the fifth and sixth segments. There are 1-3 pairs
of spermathecae, and the sperm ducts if distinct from,
are at least very like, nephridia. The ova appear to
make their way to the exterior by a large aperture
in the ventral middle line of a middle segment of
the body. The vascular system contains uncoloured
blood and is greatly simplified.

The next family to the Aeolosomatidae in z00-
logical position is clearly the Naididae. ‘These are

3—2

36 EARTHWORMS AND THEIR ALLIES [cuH.

also small worms, but show in some respects a higher
grade of organisation than their allies. While asexual
generation is general, the reproductive organs are
more commonly found than in Aeolosoma, though
there are still many hiatus in our knowledge of the
same in certain genera. Where they are known it
has been found that the spermaries and ovaries are
very far forward in the body, in the fifth and sixth
segments respectively. The spermathecae are in
segment six and the male ducts open into a terminal
chamber, called ‘atrium, which is on the whole not
unlike that of the Tubificidae. The blood in these
worms is red as in the higher types, and thus differs
from that of the genus Aeolosoma. The setae are
rather varied, being in some cases long and slender,
sometimes greatly exaggerated in length as in
Ripistes; other setae are forked at the free end,
and in Paranais this is the only kind of setae met
with. A marked feature of this family is that the
dorsal bundles of setae do not always begin like the
ventral setae upon the second segment of the body.
Indeed in Schmardaella there are no bundles of
dorsal setae at all. The Indian genus Branchiodrilus
is remarkable for the fact that it has paired processes
of the body which may be termed gills and which
in some segments involve the dorsal setae. Another
kind of gill is found in the genus Dero (which has
many species) and in the allied Awlophorus. These

I] STRUCTURAL AND SYSTEMATIC 37

are placed round the vent, and are ciliated. Other
genera are Nais, Chaetogaster, Vejdovskyella, Am-
phichaeta, Stylaria, Macrochaetina, Pristina,
Naidium.

Several genera, Pristina, Nais, Dero, are found
in many parts of the world; but it is not possible
at present to consider very seriously the facts of their
geographical distribution.

Next to the Naids a group of aquatic worms
present themselves for consideration which are
usually placed in three distinct families, which
families are however rather hard to define. These
three families are the Tubificidae, Phreodrilidae,
and Lumbriculidae. The Phreodrilidae were at one
time placed with the Tubificidae by Michaelsen. It
is now perhaps the general opinion that they form
a family of their own, at any rate since the discovery
of two other genera Phreodriloides and Astacopsi-
drilus, besides the original genus founded by myself,
and named Phreodrilus from the fact that the species
was found in a deep well in New Zealand.

The distribution of this family especially of the
genus Phreodrilus is extremely interesting. The
genus Phreodrilus is the only one genus of the
aquatic Oligochaeta which has, like Notiodrilus, a
circumpolar range, the pole being the south pole.
It occurs in New Zealand, in Kerguelen, and, if we
are to accept the opinions of Drs Michaelsen and

38 EARTHWORMS AND THEIR ALLIES [cn.

Benham that my genus Hesperodrilus is to be merged
in Phreodrilus, in Patagonia also.

In this genus the male pores are upon the xith
segment while the spermaries lie in segment Xt.
Moreover the spermathecae lie behind the male
pores. In the Tubificidae on the other hand it is
at least the rule for the spermaries and male pores
to be pushed a segment further forwards. And the
spermathecae are before the male pores. Phreo-
driloides is like Phreodrilus but has no spermathecae.
It is also New Zealand in range. Astacopsidrilus is
Australian and is semi-parasitic upon the Crayfish
Astacopsis, whence its generic name. Phreodrilus
branchiatus is one of the few forms of Oligochaeta
that possesses gills. Of these there are a series of
pairs on about the last eleven segments of the body.
They are lateral in position, and thus contrast with
the also gilled Branchiura sowerbit, where the gills,
also on the posterior segments of the body, are more
numerous and lie dorsally and ventrally, a pair to
each segment.

The Tubificidae differ from the Phreodrilidae
mainly in the points already noted. There are a
considerable number of genera of which the following
are the best known, viz, Tubifex, Limnodrilus,
Limnodriloides, Branchiura, Lophochaeta, Ilyo-
drilus, Psammoryctes, Clitellio, Telmatodrilus,
Bothrioneuron, Lycodrilus.

1] STRUCTURAL AND SYSTEMATIC ag

The Tubificidae are mainly northern temperate
forms, and a few of them such as Clitellio arenarius
and ‘ Peloryctes inquilina’’ are found on the sea
coast. There are also a few of this family in the
southern hemisphere. These forms include Clitellio
abjornsent from Australia, and a few species of
Branchiwra from New Zealand and the islands of
the Antarctic ocean. There is also to be mentioned
Rhizodrilus (or Vermiculus) aucklandicus from the
island of that name in the New Zealand area. The
only tropical species appears to be the Indian and
Malayan Bothrioneuron iris, though this genus also
occurs in Europe and in southern South America.
It is quite likely however that Branchiura sowerbi,
a species known at present from tanks in hot houses,
may be a tropical American species.

The family Lumbriculidae is yet more restricted
in its range. It has not yet been met with away from
the temperate northern hemisphere, and the great
variety of species recently described from Lake Baikal
by Dr Michaelsen is a very remarkable fact. The
Lumbriculidae are entirely fresh water in habit and
not even partially terrestrial. The following are the
principal known genera: Lumbriculus, Trichodrilus,
Rhynchelmis, Phreatothria, Claparedilla, Stylo-
drilus, Mesoporodrilus, Sutroa, Eclipidrilus, Auran-
tina, Athecospermia, Lamprodrilus, Teleutoscolex.

1 With many synonyms, including Tubifex ater (see p. 53).

40 EARTHWORMS AND THEIR ALLIES [cu.

In the worms of this family the male pores are
usually upon the tenth segment but sometimes upon
the eighth or eleventh. And in addition to a pair
of funnels in the antecedent segment there is also
commonly a second pair in the same segment as that
which contains the external pore. The two sperm
ducts however open into the same distended atrial
cavity before opening on to the exterior. In Lam-
prodrilus however each sperm duct opens by its
own separate atrium on to the exterior and in two
consecutive segments. In T'eleutoscolex there is but
one pair of funnels opening into the same segment
with the atrial pore.

Near perhaps to the Lumbriculidae comes a very
small family indeed, that of the Alluroididae. So
small is it that it consists of but a single genus
Alluroides of which there are two species A. pordaget
and A. tanganyikae. Both of these species were
described by myself, one of them from but a single
specimen, the other from only two. Both species—
and the name of one denotes the region—are from
eastern tropical Africa. The Tanganyika worm is
purely aquatic; the other species was found in a
swamp of the mainland opposite to Mombasa. This
remarkable genus has a pair of spermaries in
segment x; but the ovaries are as in earthworms in
the xuith segment. The male pores are upon that
segment also, ie. further back than in the aquatic

1} | STRUCTURAL AND SYSTEMATIC 41

worms. The spermathecae open close to the median
dorsal line of the body in one species; in A. tangan-
yikae there is but one spermatheca which opens
actually in the dorsal median line between segments
vilrand1x. This family seems to come nearest to the
Lumbriculidae but has also obvious points of likeness
to the terrestrial Moniligastridae. It fully deserves
a separate family, which was founded for it by
Dr Michaelsen.

Not obviously related to any of the other families
of Oligochaeta is the family Enchytraeidae. This
consists of a very large number of species, which are
placed in about a dozen genera, and whose habitat
is nearly confined to the cold and temperate regions
of the world. A large number of species for example
have been described by Dr Eisen from Alaska, while
others inhabit the verge of Patagonia. It is only a
few which are found in warmer countries. There is
for instance a solitary Enchytraeid in India and the
neighbouring parts of Asia described by myself as
Henlea lefroyt but doubtfully of that genus according
to Dr Michaelsen. I have also myself obtained
another Enchytraeid from British Guiana. Apart
from such rare exceptions the family is arctic or
temperate in its range and is even met with upon
the ice of glaciers. These little worms—they are
very rarely of more than minute size—are both
aquatic and terrestrial and inhabitants of the sea

42 EARTHWORMS AND THEIR ALLIES [cH.

shore. They have four bundles of short often straight
and somewhat stumpy setae; Anachaeta is entirely
without setae. That they bear some relation to the
lowest group of Oligochaeta, that of the Aeolosomas
and Naids, appears to be shown by the very anterior
position of the spermathecae, i.e. in the fourth or
fifth segment. The spermaries and ovaries on the
other hand are in segments xI and xu. They are
peculiar among the aquatic families in having complex
glands appended to the oesophagus which recall the
calciferous glands of the earthworms. The funnel
of the sperm duct is extraordinarily deep and lined
with glandular cells except in an apparently primitive
genus from Lake Baikal.

The remaining family of the Limicolae is that of
the Haplotaxidae which contains two genera, viz.,
Haplotaxis, better known as Phreoryctes, and Pelo-
drilus. These two genera overlap somewhat in their
characters and it is in the present state of our
knowledge rather difficult, if indeed possible, to
differentiate them thoroughly. They are slender
worms which frequent either damp earth or water
and are thus somewhat intermediate in habit between
the Limicolae and the Terricolae. The chief peculiarity
of their structure lies in the fact that the sperm ducts
are unprovided with any kind of terminal apparatus
whatever, but open directly upon the exterior.
Moreover there are generally two pairs of testes in

11] MODE OF LIFE 43

segments X and XI, and in some species two pairs of
ovaries in the two following segments. The small
family is very widely distributed in more temperate
regions, principally of the antarctic hemisphere. It
occurs for instance in New Zealand, South Australia,
the Cape, and in the northern hemisphere in Europe,
Western Asia, and North America.

CHAPTER II

MODE OF LIFE

WE have now completed a brief survey of the
general characters of the group of the Oligochaeta
which will at least serve to impress upon the reader
the fact that these animals are somewhat diverse in
structure, and that even as regards outward appear-
ance it is not difficult to distinguish a large number
of different types. These facts become all the more
remarkable when we reflect upon the very similar
conditions which surround all the species of earth-
worms. It is not clear how far the influence of the
soil differs in a tropical forest in South America and
in Central Africa. With divergent external conditions
anatomical differentiation becomes more accountable.
But in this case we have a lavish anatomical variation
which would appear to have no connection with any

44. EARTHWORMS AND THEIR ALLIES [cu.

kind of need that we can as yet appreciate. Com-
paring the Terricolous Oligochaeta with other large
groups of the animal kingdom, all or nearly all the
members of which lead a closely similar life, such as
the frogs and toads, or the land mollusca, or snakes,
we get a much wider range of structural change in
the Oligochaeta than in any of these.

We shall now consider their mode of life and their
relations to the environment.

The mode of life of earthworms seems at first sight
to need no special chapter or section. They simply
live in and beneath the soil, leaving it at times to
wander over the surface especially at night and
during wet weather. But there are a number of
species which habitually lead an aquatic life and
whose characteristics therefore demand consideration.

AQUATIC EARTHWORMS.

Although it is perhaps somewhat of a contradic-
tion to speak of aquatic earthworms the collocation
of words will serve to emphasise the fact that there
are species of Oligochaeta belonging to the tribe
Megadrili or terrestrial group, which are as purely
aquatic in their habits as is a Tubifex or Limno-
drilus. In such cases we may fairly assume rather a
return to an aquatic life than the persistence of such
a habit. For we do not find among these genera

11] MODE OF LIFE 45

_and species much evidence of particular resemblance
with the purely aquatic familes of Oligochaeta. It is
therefore particularly interesting to examine into
the characteristics of these water-living genera ; for
we may expect to be able to deduce from them some
hints as to what characters are really to be associated
with the purely aquatic life. We can in fact hope
to differentiate between adaptive and fundamental
characters in these animals.

These secondarily aquatic species can be referred
to two categories. There are examples of particular
species which differ from their congeners in being
aquatic; and there are whole genera, even sub-families,
which are exclusively, or very nearly so, aquatic in
habit. The former division need not detain us; for
the actual occurrence of the worms in fresh water
instead of upon dry land may be a temporary affair
and not a mark of habitual sojourn. Thus I myself
found the British and European earthworm Fiseniella
(Allurus) tetraedrus in the River Plym in Devonshire,
while it has been generally met with upon land. The
Patagonian and Falkland Island species Notiodri-
lus aquarum dulcium was so called on account of its
having been collected in fresh water. But its near
ally VN. georgianus (which is perhaps even identical
with it) was found on the sea shore in the same
region of the world. While the differences which the
small species of Notiodrilus shows from other purely

46 EARTHWORMS AND THEIR ALLIES [cu.

terrestrial members of the same genus are trifling,
further information may prove that this case is on
all fours with that of Hiseniella referred to above.
There are plenty of similar instances which I shall
not enumerate.

We may now therefore pass on to the second
category. These examples are obviously much more
important because they are of worms which appear
to be wholly aquatic, or very nearly so, and which
belong to definite genera easily distinguishable as
such from their allies. The examples are not how-
ever very numerous. And they belong practically
exclusively to the family Geoscolecidae, a family
which, it will be seen later, is confined to South
America, South Africa, Madagascar, certain parts of
India and Burmah and of Europe. It is not a family
which has reached the greater part of the East or
which has been carried to the Antarctic parts of the
globe. It is furthermore very important to bear in
mind that there are reasons for regarding this family
Geoscolecidae as one of the more modern branches of
the Oligochaeta; this latter statement tends to prove
that the aquatic life is, as already suggested, a
secondary matter in these worms, and is not due to
their belonging to an ancient race which has never
left the waters of the land.

A very interesting fact offers itself first of all in con-
sidering this family of earthworms. The Geoscolecidae

11] MODE OF LIFE 47

are one of the only division’ of the Oligochaeta
terricolae which are generally found to be without
those characteristic series of pores in the middle line
of the back known as the dorsal pores. They are
thus eminently suited for an aquatic life; for it is to
be supposed from the fact that the purely aquatic
‘Limicolae’ are also without these pores that their
existence is prejudicial to a water-living worm.
Indeed the entrance of water into the body-cavity
would presumably be dangerous to the worm. The
Geoscolecidae are thus already marked out, as it
were, for an aquatic life. No modification is here
necessary for them. It is also to be noted in this
connection that various species of the genus Notiodri-
lus to which reference has been made as a partly
aquatic genus have no dorsal pores. They too are
thus fitted for at least an amphibious life.

The rule however regarding the absence of dorsal
pores in the Geoscolecidae is not absolute. A few
species and among them two species at any rate of
the aquatic genus Sparganophilus have a few pores
between some of the anterior segments which have
been spoken of as ‘neck pores.’ They are not, it is
to be believed, of a different nature from the generally
distributed dorsal pores of other worms but are in
fact limited to the ‘neck’ region.

There are no other obvious characters of the

1 In the Eudrilidae also these pores are very frequently absent.

48 EARTHWORMS AND THEIR ALLIES [cu.

family Geoscolecidae as a whole which might be
regarded as fitting them for a purely aquatic life.

Of this family one entire sub-family, the Criodri-
linae, is very nearly purely aquatic in habit. Two
genera, viz. Callidrilus and Glyphidrilus, out of
another sub-family, Microchaetinae, which contains
perhaps five other genera, are also aquatic in their
mode of life. In examining into the characters of
the various aquatic species with a view to searching
for common characters which might be put down to
modifications induced by the aquatic life, there are
two or three which arrest attention. In the first
place the Criodrilinae never possess a well-developed
gizzard, having at most a rudimentary gizzard, or
even two. However this character is not of universal
applicability, for both Callidrilus and Glyphidrilus
have got a gizzard and a strong one. These later
genera however have no calciferous glands or oeso-
phageal pouches of any description, structures which
are also absent among the Criodrilinae. It will be
remembered that the purely aquatic families,
Tubificidae, Lumbriculidae, etc. rarely show
signs of a gizzard and rarely possess oesophageal
pouches of any kind. In view of the fact that in
the case of a life in fresh water no calcareous salts
are necessary to resist the acids of the soil, and
that the mud passed through the alimentary canal
is already finely divided, it is not surprising to

Ir] MODE OF LIFE 49

find gizzard and calciferous glands absent or rudi-
mentary.

Another not unusual feature among these aquatic
Geoscolecidae is the quadrangular form of the posterior
end of the body. This is shown—as its specific name
denotes—by Glyphidrilus quadrangulus, by species
of Alma and in all the species of the genus Criodrilus.
It is to be noted in this connection that a species of
the partly aquatic Hiseniella has been named tetrae-
drus on account of precisely the same phenomenon.
In these cases it is the posterior part of the body
which is thus quadrangular ; the anterior segments
down to the ninth in Criodrilus being rounded in
the usual Oligochaetous fashion. As the paired setae
are apt to lie in the four projections of the quad-
rangular body, one is tempted to see in this arrange-
ment of structures a faint approach to the dorsal and
ventral parapodia of the marine worms, and in any
case it seems possible that by this means the worms
can cling more effectively and continuously to the
stems and leaves of aquatic plants among which they
so largely live.

It is a very remarkable fact that in the genera
Criodrilus and Alma the vent is dorsal in position
instead of being surrounded as in earthworms
generally by the last segment of the body. This fact
might be put down to the near affinity between these
two genera, were it not for the fact that Glyphidrilus

B, E. 4

50 EARTHWORMS AND THEIR ALLIES [cu.

shows precisely the same state of affairs. These facts
gain additional significance in my opinion from the
fact that among the leeches which are now univer-
sally admitted to be allies of the earthworms the
same position of the vent is met with. This abnormal
position of the end of the alimentary canal may thus
be fairly quoted in connection with structures modi-
fied by the aquatic life.

Finally, and this seems to be very important, the
only genus among the Megadrili which possesses gills
is the Nile worm Alma nilotica.

MARINE SPECIES.

There are a few, but relatively speaking very few,
worms of the order Oligochaeta which lead a marine
life. And of these the majority are shore forms not
extending into the waters of the sea. The most
salient example, at any rate the best known perhaps,
is the genus Pontodrilus, the name of which fixes its
habitat, and was naturally given to it on that account.
It was originally found on the sea shore of the South
of France, and [have myself examined examples from
Nice. The worm lives among bunches of sea-weed cast
up by the sea, and which are thoroughly salt. Besides
the two forms that have been met with in this Mediter-
ranean region but which are united by Dr Michaelsen
into but one species, other Pontodrilus have been

11] MODE OF LIFE 51

described from so many and such diverse parts of the
world as the following. The West Indies (Bermudas,
Jamaica etc.), the coasts of South America, of both
West and Eastern Africa, the Red Sea, Christmas
Island near Java, Sharks Bay in West Australia, the
Hawai Archipelago, Celebes, South West Australia
etc. In fact there is no great tract of the ocean
excepting the antarctic region where this genus is
not to be found. It is possible however that this
latter statement is not correct and that New Zealand
ought to be added. But the species described from
those islands, viz. Pontodrilus lacustris, is not a marine
form at all as its specific name denotes; nor is it
quite certainly to be included in the genus. On the
other hand a form from the Chatham Islands in the
same quarter of the globe, described originally as
Pontodrilus chathamensis, is to be referred to the
antarctic region. Altogether some dozen species of
Pontodrilus have been described by different natural-
ists; but quite recently Dr Michaelsen has reduced
these to three only, which are P. bermudensis (F. FE. B.),
P. litoralis (Grube) and P. matsushimensis (Izuka),
with the doubtful addition of P. lacustris already
referred to. Whatever may be the ultimate verdict
upon this question of species it is clear that the genus
is widely spread upon the sea shores of the world
and that forms from different regions show some
fixed variations, which others may eventually agree
4—2

52 EARTHWORMS AND THEIR ALLIES [cx.

with their original describers in regarding as definite
species.

It cannot be said that any salient characters in
the organisation of these worms mark them out from
either terrestrial or fresh-water Oligochaeta. There
are no such important variations of structure as can
be seized upon to characterise them as inured to
salt water. The genus agrees with many aquatic
forms in the fact that the nephridia are not present
in the earlier segments of the body, not indeed putting
in an appearance until about the thirteenth segment
or even later. They are thin delicate worms; but
there is nothing distinguishing about this, while the
feeble or absent gizzard is a character which is really
difficult to correlate with habitat. Still we have here
a whole genus which is marine in its habit. Among
the Megadrili or earthworms there are not many
other examples of these ‘euryhaline’ forms as they
have been named. On the shores of Patagonia how-
ever and Kerguelen shore-living species of the mainly
antarctic genus of earthworms Notiodrilus have been
met with. And there are a few allied cases among
the antarctic genera of Acanthodrilinae.

In addition to these terrestrial forms there are
a few limicoline genera which are partly marine in
their habit. Thus several species of the prevalently
arctic and antarctic family Enchytraeidae are shore
living. There are also marine Tubificids such as

It] MODE OF LIFE 53

Clitellio arenarius and Tubifex ater (not uncommon
on British shores), marine Lumbriculids and a marine
Naid from the Italian coast. These forms show no
great differences from their fresh-water allies.

EARTHWORMS ORIGINALLY PURELY AQUATIC
ANIMALS.

The very name Earthworm, so distinctive as it is
of the habitat of these animals, seems to have been
expressly invented in order to crystallise into one
word the remarkable distributions of these creatures.
They are with very few exceptions the most purely
terrestrial animals that we know. There are a few
Mammals like the mole and several underground
Amphibians and Snakes in the tropics which share
this habitat with the worms, probably because they
chiefly prey upon them. But there is no group of
animals that is characterised by a subterranean
existence in the way that earthworms are. For we
cannot put burrowing animals, such as the prairie
dog and many rodents, into the same category.
These make and seek their burrows for protective
purposes and in order to bring forth their young in
security. They do not feed beneath the surface of
the ground or pass their entire lives in that situation.
We have already in a previous chapter dealt with
such exceptional forms of earthworms as do not lead

54 HKARTHWORMS AND THEIR ALLIES [cn.

an entirely subterranean existence ; but as was pointed
out in chapter I these exceptions are but few and
the immense bulk of earthworms fully justify their
name.

Nevertheless there are many arguments which
tend to show that these purely land-dwellers have
grown out of exclusively water-dwellers and even
that the change from the one mode of life to the
other has been accomplished comparatively recently.
For there are here and there vestiges of structures
which seem only fitted for an aquatic life; and in
other cases structural changes have commenced
which would appear to be in definite relation to the
underground mode of life prevalent to-day. Let us
consider for a moment the differences which obtain
between the conditions of life in water or in soft mud
at the bottom of pool or river, and those which are
undergone by a dweller in stiff soil or vegetable
débris. In the first case the medium is fluid or at
most very soft, while the soil is at least stiffer and
harder to traverse.

Secondly the transition between the very bottom
of a pool and the top layers of the water is more or
less gradual, while the stiff soil ends abruptly in the
tenuity of the atmosphere.

A third point of difference is doubtless the smaller
supply of readily available oxygen in the still pools
and even rapid rivers, which in certain stagnant pools

11] MODE OF LIFE 55

and in the bottom waters of deep lakes must produce
a very vast difference in physiological conditions.

We have already dealt with the characteristics
of the aquatic genera of earthworms, not only in
detailing the general characters of the families which
are found in this situation but also in studying the
features which earthworms show in those cases where
they have reverted to an aquatic mode of life. It
remains in the present section to attempt to descry
in the purely terrestrial forms the remnants of
adaptations to an aquatic life which are no longer of
service to them.

It is a noteworthy fact, that the continuous circle
of setae which is met with in certain earthworms
is by no means a character of such classificatory
importance as it was at one time, perhaps, thought
to be. It is true that we meet with this character in
the genera Megascolex and Pheretima which are not
very far from each other in the ystem and are at
any rate members of the same sub-family, the Mega-
scolecinae. But we also find the continuous circle of
setae well developed in Plagiochaeta which is not so
near to Pheretima, and an approach towards it in
Dinodrilus and Dinodriloides which are equally
remote perhaps from both Pheretima and Megascolex
on the one hand and Plagiochaeta on the other.
Still it may be urged that all of these genera are at
least members of the family Megascolecidae and that

56 EARTHWORMS AND THEIR ALLIES [cu.

the question of a character which thus merely shows
affinity is not yet eliminated. It is therefore of
particularly great importance that Dr Cognetti de
Martiis should have met with the South American
genus Periscolex which, undoubtedly a member of
a totally distinct family, the Geoscolecidae, yet shows
the same complete circle of setae. The reason for
dwelling upon this particular anatomical character
in the present connection is because it would seem to
be a character specially suited to an underground life
where there is an equal pressure all round the body
and where progression would seem therefore to be
best attained by a continual leverage round the
circular body. And this view is strengthened by the
sporadic occurrence of this modification in different
families. We thus come to the conclusion that the
opposite state of affairs is a remnant of an aquatic life,
a conclusion which it is the object of the present section
to discuss. More than this, it would seem that an equal
disposition of the two bundles of setae on each side
of the body was a less modified state of affairs than
the restriction of the two bundles or pairs of setae to
the ventral surface, such as occurs for example in the
genus Dichogaster and which is very obvious in some
of the larger-sized members of this extensive genus.
For the restriction of the setae to the ventral surface
obviously favours progression upon a surface and not
through a medium. And it is only among the

It] MODE OF LIFE 57

terrestrial Oligochaeta that this mode of progression
occurs. It might also be urged, and with some
reason, that the retention of rather longer setae
upon the clitellum in the Lumbricidae and Geoscole-
cidae, and the possession of equally long or in many
cases much longer setae corresponding to one of the
two pairs of setae of the generative segment in certain
Megascolecidae, is a feature in which an aquatic
condition—so to speak—is retained. The setae would
represent a vestige of the general presence of long
setae over the body generally such as is convenient
or at least not inconvenient to an Annelid living in
water or soft mud. But probably it will be thought
the modified genital setae are a recent development
and not a retention.

There is no more thoroughly terrestrial family of
earthworms than that of the Moniligastridae and yet
this family in its general anatomical characters shows
many points of likeness to aquatic forms as has been
now pointed out by many observers. It is true that
these characters are not those which might be
associated at first sight with an aquatic life. But
none the less they are characteristic of most of the
families which live in the waters of the earth. Thus
Moniligaster and its allies (Hupolygaster, Drawida,
etc.) have quite short sperm ducts which open on to
the exterior at furthest in the segment next to that
in which their internal funnel lies. Again the

58 EARTHWORMS AND THEIR ALLIES [cu.

simple structure of the terminal gland into which
they open and which in its turn opens on to the
exterior is very like that of such a family as that of the
Lumbriculidae. Another fact is the simple undivided
cavity of the sperm sacs which is unlike that of
typical earthworms but again like that of all of the
Limicolous families. We may fairly see in these
worms evidence of origin from aquatic ancestors.
Evidence of the same nature, 7.e. not as showing the
retention more or less of anatomical characters
commonly associated with a life in water, but as
affording indirect evidence of an origin from actually
aquatic forms, is to be seen in certain members of
the families Geoscolecidae and Eudrilidae. In both
of these it not infrequently happens that the sperm
sacs are but a single pair and that that pair consists
of sacs of extraordinary length. Thus in 7'richochaeta
(or Hesperoscolex) barbadensis Miss Fedarb and I have
shown that the long thin sperm sacs extend through
no less than 109 segments, which is vastly in excess
of the length of those of the majority of earthworms
in which they are most commonly limited to a single
segment. In the same way the Eudrilid worm Poly-
toreutus magilensis has a pair of long and thin sperm
sacs which extend through some fifty segments. This
elongation of the sperm sacs in the ripe worms is a
very common feature of the Limicolous genera.

iT] EXTERNAL FEATURES 59

CHAPTER. IIT

THE EXTERNAL FEATURES OF EARTHWORMS AND
THEIR RELATION TO HABIT AND ENVIRONMENT

To the very inexperienced eye all earthworms
might appear to be quite similar in detail as they
undoubtedly are in general form. But it needs not
a great deal of examination to detect even salient
characteristics whereby one kind may be distinguished
from another; to the expert it is possible in very
many cases to go no further than the outside before
assigning its correct place in the system to a given
example. The general external features of this group
of worms have been already dealt with in another
chapter. To some of these we again direct attention
in a more elaborate fashion in order to emphasise the
possible meanings of the variations met with apart
from their use in systematic arrangement. It is
difficult to say in comparing one worm with another
what is the most salient external difference. There
are however a few which may be regarded as equally
conspicuous on a hearer examination of the specimens.
The varying position and greater or less extent of
the clitellum, the longer or shorter retractile or non-
retractile prostomium, the position of the usually
conspicuous male pores, and the,existence of in the

60 EARTHWORMS AND THEIR ALLIES [cu.

first place and—when present—the numbers and
situation of the so-called genital papillae are among
the most obvious. The setae and their position we
treat of under the heading of the modification of the
worms to lead a terrestrial life; and though these
chitinous organs differ greatly they do not concern us in
the present section. The girdle or clitellum (‘eminentia
quasi ulcerata’) has been long observed as a character
of these animals and it is one which distinguishes
them from all other worms except the leeches and
a very few marine Polychaeta. This modified region
of the body is often of a different colour to the rest
and has a glandular look which readily enables one
to recognise its position and limits, though its
obviousness is less in some cases. It either forms
a complete ring round the body or is developed upon
the dorsal surface and only to a slight extent upon
the ventral surface. Its use, as is well known, is to
secrete the cocoon in which the eggs are deposited ;
and the epidermis which forms it is thickened and
more glandular than that in other regions of the
body. Among earthworms it is doubtful whether the
clitellum ever occupies less than three segments; it
consists of three only in the great majority of species
of the marked genus Pheretima. From this lowest
level it extends in other forms, and in the partially
aquatic African genus Alma it may occupy as many
as forty segments. The position also varies from

1] EXTERNAL FEATURES 61

genus to genus and from species to species. It is
sometimes further forward and sometimes further
back. In the remarkable family Moniligastridae this
organ is developed earlier in the body than in any
other group of true earthworms, consisting of four
segments or so commencing with the tenth. As a
rule the clitellum begins further back.than this—the
thirteenth or fourteenth being a common place for
the first commencement of the organ among the
Megascolecidae, while among the Geoscolecidae and
Lumbricidae it is generally much further back,
commencing in Alma at the forty-fifth. These
details might be increased to many pages; but enough
has been said to emphasise the variability of the
organ. What reason can be assigned to this varia-
bility, which might be supposed unnecessary in view
of its functions? There are perhaps two suggestions
that may be made, though many facts are lacking
which might offer confirmation or refutation of either
of these. It is to be noticed that on the whole the
older types such as the Moniligastridae and the
Megascolecidae (including for this purpose the
Eudrilidae) have clitella which are short. There
are a few but not many exceptions. These older
types do not seem capable of extending their range
with any rapidity. It is true that here again there
are exceptions, notably many species of Pheretima
which are considered under the section which deals

62 EARTHWORMS AND THEIR ALLIES [cu.

with the migration of these animals. On the other
hand the Lumbricidae have on the whole a more
extensive clitellum and so have many Geoscolecidae.
It is obvious that of all earthworms the Lumbricidae
is the family which has the greatest capacity of
migration and adaptation to new circumstances.
The reason for this may be that in the latter case
the more extensive clitellum produces alarger cocoon
which in its turn can hold and cherish while they
reach maturity a larger number of embryos. Much
remains to be learnt under this heading. But the
comparatively small clitellum of the large Ceylon
Megascolex coeruleus only contains two embryos,
while the also comparatively small cocoon of the
large and restricted Octochaetus multiporus (limited
to the South Island of New Zealand) only contains
a single embryo. This latter fact may be regarded
as fairly well established since I myself examined
quite fifty cocoons.

On the other hand larger numbers seem to arrive
at maturity in the cocoons of Allolobophora. The
more extensive clitellum must produce a relatively
larger cocoon, and it is interesting to note that the
cocoon of the widely distributed genus Criodrilus
(Europe and South America) is very long although
not of great diameter. However the facts are not
sufficiently great to dogmatise much upon. this
subject. Another conceivable reason for differences

m1] EXTERNAL FEATURES

—

3°: seers

ai

mapa
FS

Fig. 12. Fig. 13.
Fig. 12. Ventral view of Pheretima solomonis to show papillae
which are to be compared with those of fig. 13. (x 2.)
Fig. 13, Ventral view of Pheretima sedgwickii. (x 2.)

63

64 EARTHWORMS AND THEIR ALLIES [cu.

in the clitellum is—as I also think is the case with
the genital papillae—to prevent hybridisation. That
the sense of touch is delicate in these animals
seems clear from the abundant development of
epidermal sense-organs. It may be that the feel of
the clitellum during union enables two individuals of
a given species to come together and prevents those
of different species from mating. In any case there
is no positive evidence that hybridisation does occur
in this group of animals. The astounding variability
and yet constancy in a given species of the genital
papillae is in favour of regarding these organs as
tactile recognition marks ; and it will be noted that
they are not by any means characteristic of some of
the older types of earthworms. Furthermore they
are particularly conspicuous in such genera as
Pheretima, Megascolex etc., which possess a large
number of species. In these of course mutual
recognition would otherwise be more difficult.

CHAPTER IV

SENSE ORGANS AND SENSES OF EARTHWORMS

As this is not an anatomical treatise we shall not
attempt any detailed anatomical and _ histological
account of the sense organs in this group of worms.

Iv] SENSE ORGANS AND SENSES 65

But a few facts must be given in illustration and
explanation of the senses of touch and sight that the
Oligochaeta undoubtedly possess. These Annelids,
unlike their allies the marine Polychaeta, and even
their allies on two other sides, the leeches and flat-
worms, have no complexly organised eyes or other
sense organs. They have in fact no organs to which
a definite sense can be attached on_ histological
grounds. There is nothing comparable to an eye or
to the auditory sacs of other low worms. There are
only particular cells of the epidermis, often associated
into small groups, and those again into larger associa-
tions of rows of such groups of cells. It is to be
presumed that these modified groups of cells have a
sense function; but no more can be said than that
they are doubtless tactile and also to some extent
receptive of the influence of light. True visual cells
have been asserted to exist in earthworms, consisting
- of cells of which a part is clear and transparent and
has been supposed to serve as a lens for the rest of
the cell which represents a retina. But belief in the
function of these cells is by no means unanimous.
On the other hand many investigations have proved
the existence of groups of epidermic cells of an oval
form which are at present arranged in definite rows
upon the segments of both terrestrial and aquatic
forms, which are moreover connected with nerve
terminations, or are at least—according to more

B. E. 5

66 EARTHWORMS AND THEIR ALLIES [cu.

modern views—in close contact with the terminations
of nerve fibres. These are furnished often at their
free tips with minute sensitive processes. There is
nothing in the structure of these to associate them
definitely with any sense in particular. They suggest
of course tactile organs more than organs of any
other sense. In addition to these are certain pro-
blematical organs which are found in the Eudrilidae
and are present in the members of one section of
that group, the section which is represented by the
universally found Hudrilus.

These bodies have been compared to a Pacinian
body (a sense-organ found in Vertebrates) and they
bear no little resemblance to it. For each consists
of a darkly staining core surrounded by a layer
of cells arranged like the coats of an onion. In
any case it would appear that these bodies must
be looked upon as of a sensory nature, though they
do not reach the surface of the body but underlie
the epidermis. Their function must remain purely
a matter of guesswork at present, for nothing to the
point is known of the habits of the Eudrilidae. It
has been suggested by Dr Gustav Eisen that these
cells are auditory and serve to warn the worm of the
footsteps of birds and other enemies. That too is
his view of certain peculiar but different cells found
in the epidermis of Pontoscolex. In the latter some-
thing like an otosome has been found which is

Iv] SENSE ORGANS AND SENSES 67

certainly lacking in the Eudrilidae, whatever may be
the function of the cellular epidermic bodies here
briefly referred to.

While there is thus nothing very positive to be
gleaned from an examination of the structure of the
Oligochaeta as to the senses which they may possess,
experiment has done something towards an elucida-
tion of their behaviour under stimuli and _ their
reaction to light and to other forces which come into
play during their lives. There is some evidence that
earthworms can see, using that expression of course
in a very broad way. At any rate they react to
changes in the intensity of light. The gross experi-
ment of flashing a lantern upon earthworms which
are reaching out from their burrows with the tail
end inserted in those burrows shows that they have
an appreciation of light. More refined experiments
have been conducted upon the sense of light.
Dr Graber used a box with two compartments, the
one of which was dark and the other illuminated
with diffused daylight, @e. not direct sunlight. The
worms were allowed equally free access to both and
were examined at the close of every hour, and their
positions noted. The investigator found that on the
average the dark half of the box contained 5:2 times
as many worms as the light chamber, thus indicating
a very marked preference for absence of light.

Not only is this the case, but the same observer

ry ~»)

” a

68 EARTHWORMS AND THEIR ALLIES’ [cu.

proved that earthworms can distinguish between
degrees of intensity of light. This obviously indicates
a more complete ‘visual’ sense. He illuminated
the light-box of the former experiment with light
admitted through a ground glass screen, thus di-
minishing its intensity. The other chamber was left
as before but the screen was removed, thus admitting
full daylight. In this experiment the number of
worms in each compartment proved to be different.
The results were not so striking as before, since only
rather more than one-half were found in the more
dimly illuminated chamber. It is a well-known fact
that if earthworms are abroad at all from their
burrows, it is during the night that this movement
takes place, the numbers decreasing towards morning
though worms are often seen crawling about well
after sunrise. Some experiments have been made in
attempt of explanation of this apparent anomaly. It
would appear from these experiments that while
worms are negatively phototropic to strong and
moderate light as has already been pointed out, they
are positively phototropic to very dim light; hence
the advent of evening calls them forth from their
burrows. It will be noted that this perception is of
very great advantage to the worm since its more
active enemies above ground are diurnal. It was
held originally that the head end of the worm only was
thus sensitive to light ; but more recent experiments

Iv] SENSE ORGANS AND SENSES 69

have shown that this is not the case, and that
all of the body is sensitive. This disposes of course
of the existence of special light-receiving organs in
the anterior part of the worm’s body. Not only this,
but an interesting extension of the view has been
promulgated. It has been shown by Prof. G. Parker
and a colleague that in the common Brandling worm,
Allolobophora jfoetida, the response to light stimuli
was related to the amount of the body exposed to its
influence. This is very important as showing that
the light perception in these creatures is probably
not due to special organs having a limited position
on the body, but is due to collective sense impressions
of many cells scattered over the whole body, the
impression being the greater when the whole body
is exposed and less when only parts of it are exposed.
Furthermore, and this has quite another importance,
these observers noted that the reaction effects differed
when only a part of the body was exposed ; that they
were greater in the front of the body, less -in the
middle, and less still at the tail end. Indeed they
found that the reactions in the case of the front end
of the body alone being exposed were rather more
than one-third as compared with those which were
shown when the whole body was subjected to the
light stimulus. The fact that the least sensitive
region of the body is the posterior end has, it is
true, only been definitely proved in the case of the

70 EKARTHWORMS AND THEIR ALLIES [cu.

worm whose specific name has been mentioned. But
it is possible that others are similarly affected. And
it is highly important to note the prevalent habit
among the Tubificidae of lying with the head end
imbedded in the mud of the pool which they inhabit,
while the tail end emerges and waves freely in the
flood. The additional fact that this tail end occasion-
ally bears gills (as in Branchiura sowerbii and
Phreodrilus branchiatus) has a collateral importance
not to be mistaken.

CHAPTER V

RELATIVE FREQUENCY OF EARTHWORMS IN
DIFFERENT REGIONS OF THE WORLD

It will be of use for various purposes to be con-
sidered later to arrive at a comprehensive view of
the relative numbers of species and genera of earth-
worms in the four quarters of the globe. And in
making this general census we shall not take into
consideration the purely aquatic forms, but shall
limit ourselves to the earthworms, sensu stricto, or
Megadrili, of which, however, it is true that some
members are actually lake and river dwellers. This
latter fact will not, however, interfere with the
usefulness of the comparative survey.

vi RELATIVE FREQUENCY 71

Two preliminary remarks are necessary. The
opinions of naturalists vary as to the limits of
genera ; and a species may be a species to one and
a mere variety to another. Thus it will be impossible
to give a summary of the facts to be enumerated
presently, which will be either absolutely accurate or
which will satisfy everyone in every detail. But it is
asserted that the following survey is substantially
correct.

In the second place it is often possible to elim-
inate from the fauna of a given region those species
and even genera which have been accidentally
imported, a matter which will receive careful con-
sideration on a later page. Such forms are therefore,
in those cases at any rate where the evidence seems
to be overwhelming, withdrawn from the list. In
other cases, particularly in the Eastern region of the
world, it has been found less easy to rectify the
catalogues by removing what Dr Michaelsen has
termed ‘peregrine’ forms.

We shall commence with a census of South
America; the entire Continent will be divided for
the present purpose into three divisions, viz. South
America, Central and North America, and in the
third place the West Indian Islands.

In South America we find that the bulk of the
indigenous earthworms belong to the family Geoscole-
cidae and to a definite sub-family, viz. Geoscolecinae.

72 EARTHWORMS AND THEIR ALLIES [cu.

These genera are Onychochaeta with one species,
Hesperoscolex of which one species is known from
the area, Periscolex with one species, Anteotdes with
two species, Pontoscolex one species. Opisthodrilus
with two species, Rhinodrilus (including either as
synonyms or as sub-genera, Thamnodrilus, Anteus,
Tykonus, Urobenus and Aptodrilus) with no less
than 49 species: Andiodrilus with five species,
Holoscolex with one species, Glossoscolex ten species,
Fimoscolex, Andiorrhinus and Enantiodrilus with
one species apiece.

Thus of this sub-family of Geoscolecidae we have
in South America a large number of genera and a
much larger number of species. Of a second sub-
family of Geoscolecidae there are three species of
Criodrilus found in the South American Continent.

We now turn to the Megascolecidae of which a
large number of species occur within the area now
under consideration. The bulk of these belong to
the sub-family Acanthodrilinae and they are as
follows :

Of the genus Notiodrilus there are ten species,
of Microscolex two species, of Chilota 19, of Yagan-
sia 13.

A second sub-family Trigastrinae also occurs in
this Continent and the following genera are permanent
inhabitants, viz. :—

Dichogaster (= Benhamia) with only three species,

v| RELATIVE FREQUENCY 73

of which two at least are found elsewhere, and of
which therefore the autochthonism is doubtful.

Finally, there is the sub-family Ocnerodrilinae
comprising the following genera: Kerria with ten
species, Ocnerodrilus (with sub-genera Liodrilus,
Ilyogenia and Haplodrilus) four species, which again
are rather doubtful indigenes of the South American
Continent.

Leaving aside certain species (of the genera
Inumbricus, Pheretima, etc.) which are clearly not
indigenous, the South American Continent harbours
150 kinds of earthworms which are distributed in
some 19 genera. But of these a few species (e.g.
Onychochaeta windle, Kerria macdonaldi) stray imto
neighbouring regions, ¢.e. the West Indies and Cali-
fornia. It is doubtful therefore whether they are to
be referred to as limited to one of these regions and
accidentally imported into the others, or whether they
are genuine inhabitants of both.

The South American Continent shares with the
West Indies the following genera,.but the species
(except in the case of Onychochaeta windlei, Glosso-
scolex peregrinus) are distinct; these genera are
Hesperoscolex, Pontoscolex, Dichogaster, and Ocnero-
drilus. Diachaeta is limited to the West Indies.

The following South American genera are also
found in Central and warmer North America
(Mexico, California), viz. Hesperoscolex, Periscolex,

74. EARTHWORMS AND THEIR ALLIES [cu.

Rhinodrilus, Pontoscolex, Andiodrilus, Glossoscolex,
Notiodrilus, Microscolex, Dichogaster, Kerria and
Ocnerodrilus. But with the exception of Hesperosco-
lex, which seems to belong rather to Central America
and the West Indies, Microscolex and Pontoscolex
which are world-wide and whose original home is
therefore difficult to fix, and Dichogaster and Ocnero-
drilus which would seem rather to be rare immigrants
(perhaps not truly indigenous) into South America,
these genera are practically distinctively South
American.

Thus we may fairly say that the genera A nteoides,
Opisthodrilus, Andiodrilus, Holoscolex, Glossoscolex,
Rhinodrilus, Andiorrhinus, Fimoscolex, Enantio-
drilus, Notiodrilus, Chilota, Yagansia and Kerria
are at least very distinctive of 8. America and that
they are represented by the large majority of species
found in that continent, the total being 120 or slightly
more.

Leaving the American Continent and adjacent
islands and archipelagos, the next great land-mass
to receive attention will be the Continent of Africa.
In giving a census of the species and genera of earth-
worms which inhabit this quarter of the globe it
must be premised that the facts relate only to Africa
south of the Sahara. But little is known of the
genera which occur in Algeria and Morocco, but from
what little is known it is clear that they should come

v] RELATIVE FREQUENCY 75

into consideration in connection with the fauna of
Europe and not with that of tropical and south
temperate Africa.

We have in the first place to consider an entirely
peculiar family, of fair extent in genera and species,
which is limited to this region of the world; that is
to say with one apparent exception which is clearly
only apparent. The genus Hudrilus is one of the
few kinds of worms that turns up in collections from
every tropical part of the world and even at times
from more temperate countries. It is one of those
‘peregrine’ forms, as Dr Michaelsen has termed them,
which possess unusual facilities for extending their
range. Presumably its real home is Africa. This
family is known as the Eudrilidae though by some it
is only regarded as a sub-family of the Megascolecidae.
In this family we have the following genera: Hudri-
loides with 11 species, Platydrilus with 11 species,
Megachaetina with two species, Reithrodrilus with
one, Stuhimannia with five species, Notykus and
Bogertia with one species each, Metadrilus also
with but one species, Pareudrilus with perhaps five,
Libyodrilus with one and Nemertodrilus with two
species, Metschaina with two species, Hudrilus with
two (or possibly more?) species, Parascolex with
four species, Preussiella with two, Buttneriodrilus
with two, Himinoscolex with 16 species, Hyperio-
drilus, Heliodrilus, Alvania, Rosadrilus, Kaffania,

76 EARTHWORMS AND THEIR ALLIES [cH.

Euscolex, Metascolex, Beddardiella, Gardullariawith
only one species to each genus, Bettonia with three
species, Teleudrilus with 15 species, Polytoreutus
with 22 species, I7idodrilus with two, Malodrilus also
with two, Newmanniella with eight, Eupolytoreutus
with two and Teleutoreutus with only one species.

This completes the list of the Eudrilidae. We
will take the huge family Megascolecidae next ; and
we find in tropical Africa that the genus Dichogaster
alone contains at. least 93 species confined to Africa,
as well as a few which it shares in common with
America, and the common and widely spread D. bolavi
which has even made its way to Europe. Of the sub-
family Ocnerodrilinae we have the genus Gordiodrilus
with seven species, a genus which also occurs in
Madagascar and the West Indies : Nannodrilus with
three species, Diaphorodrilus with one species and a
few examples of Ocnerodrilus and its sub-genera, some
of which are also forms that occur elsewhere in the
world, for example Nematogenia panamensis. Of
Pygmeodrilus there are eight or nine species.

Of the sub-family Acanthodrilinae the Cape region
of South Africa harbours some seven species of the
genus Notiodrilus, of which one however is a West
African form. The allied Chilota has 13 species, and
there is a peculiar genus Holoscolex near to Yagansia
with one species. We next have to deal with the -
Geoscolecidae, of which a sub-family, Microchaetinae,

Vv] RELATIVE FREQUENCY id

is mainly found in Africa, the rest being found in the
neighbouring Madagascar and some few in the East.
Microchaetus contains about 14 species, Tritogenia
perhaps three, Callidrilus two, and the genus Glyphi-
drilus, mainly found in Asia, has one species in the
region now under consideration. In addition to these
Geoscolecids there is the peculiar and largely aquatic
Alma with six or seven species in East, West, and
Central, Africa, and in the Nile region.

Summing up the genera which are found in
tropical and South Africa we find that there are 44
which are abundant in, or entirely confined to, the
region. In addition to these four or so occur in
Africa but are either more abundant elsewhere or
(as in the case of Chilota and Notiodrilus) are equally
distinctive of other parts of the world. The number
of species may be estimated at 270, possibly rather
more. ‘ Clearly therefore this part of the world is
much richer than South America, both in numbers
of genera actually found, and peculiar to the country,
and numbers of species.

Passing from Africa the next definite quarter of
the globe which will detain us here is the island of
Madagascar, so remarkable for the Mammalian fauna
which characterises it, for its lemurs, peculiar Insec-
tivora and Carnivora, and above all by reason of the
absence of the prevalent African types such as
antelopes, zebras, rhinoceros etc. It is probable

78 EARTHWORMS AND THEIR ALLIES. [cH.

that a good deal still remains for discovery among
the earthworms of this island; but a considerable
number are already known and they are as follows:

The Eudrilidae are completely absent, a state of
affairs which is paralleled by the absence of antelopes
among mammals.

The sub-family Acanthodrilinae of the family
Megascolecidae are represented by four species of
the genus Notiodrilus, with which perhaps Maheima
braueri from the Seychelles should be included as
it presents small differences from Notiodrilus.

Among the Megascolecinae a good many species
of Pheretima have been collected both on Madagascar
and on certain adjacent islands ; but these, with one
possible exception, are forms which occur elsewhere
and are often indeed very widely distributed ‘ pere-
grines, so that it is hardly permissible to place them
among the real inhabitants of Madagascar. The
same arguments hold in the case of Lampito mauritit
and the ubiquitous Ludrilus and Pontoscolex. But
there is the peculiar Howascolex.

Among the Ocnerodrilinae a distinct species of
Gordiodrilus occurs, and an obviously introduced
Ocnerodrilus.

It is among the Geoscolecidae that the most
characteristic forms are met with. These belong
exclusively to a genus of the Microchaetinae, Kynotus,
which is found nowhere else but in Madagascar,

v| RELATIVE FREQUENCY 79

where it is represented by at least twelve different
species.

We have therefore in Madagascar and the sur-
rounding islands only two peculiar genera, only four
genera which can be regarded as endemic, and only
about seventeen peculiar species.

Passing eastward and crossing the Indian Ocean
we come to the Continent of Asia, and we shall first
direct attention to the peninsula of India and ad-
jacent parts of Burmah and the island of Ceylon, of
which there has been accumulated a great deal of
knowledge concerning the Oligochaetous fauna.

This quarter of the globe differs quite as much
from any that have been hitherto considered as they
do among themselves. We have left behind us the
Geoscolecidae with the exception of the ubiquitous
and clearly peregrine Pontoscolex, and the genus
Glyphidrilus, which, being aquatic at times, is perhaps
hardly to be considered in the present survey.

We have also in this Indian region the equally
ubiquitous Hudrilus eugeniae which need not of
course detain us further. The Lumbricidae are for the
most part of European forms with the exception of
Helodrilus indicus conceivably an actual inhabitant
of India. It is among the Megascolecidae that the
vast majority of the forms endemic in India are to
be found. We shall take this family according to
its sub-families. In the first place we note that the

80 EARTHWORMS AND THEIR ALLIES [cu.

sub-family Acanthodrilinae is totally unrepresented.
The large sub-family Megascolecinae has very numer-
ous representatives. Of the genus Megascolex itself
there are some 30 species, of which, however, two or
three are looked upon as varieties. Of the allied
genus Notoscolex there are ten species and of Peri-
onyx about 13. The genera Megascolides, Diporo-
chaeta, Spenceriella and Woodwardia have only six
species between them of which three belong to Mega-
scolides. Plutellus has five species in this region.
Lampito, which is a widely spread form with but one
species LZ. mauritii, may or may not find here its
original home. It also occurs in Africa and Mada-
gascar. Pheretima is represented by no less than
12 species, of which at any rate the very great
majority are peregrine forms, and not to be safely
regarded as forming an integral part of the fauna
of the Indian peninsula and adjoining countries.

Of the sub-family Octochaetinae the type genus
Octochaetus has ten species in this region and Huty-
phoeus, which is restricted to the region, has 15
species or perhaps rather more. Hoplochaetella has
but one. Of the Trigastrinae there are four or five
examples of the genus Dichogaster which occur
within the region now under consideration ; but it
is doubtful whether they are truly indigenous. On
the other hand Hudichogaster, closely allied both to
Dichogaster and Trigaster, seems to be confined to

Vv] RELATIVE FREQUENCY 81

this part of the world where it is represented by five
species. Finally we come to the last sub-family—that
of the Ocnerodrilinae, which is represented by a
species apiece of the genera Ocnerodrilus, Nemato-
genta and Gordiodrilus. The latter species G.
travancorensis is alone to be regarded as endemic
and it is very near to the African G. zanzibaricus,
described some years since by the present author.

The remaining family of terricolous Oligochaeta
found in India is the family Moniligastridae which is
practically limited to this part of the world and
consists of at least twenty species distributed among
the genera Moniligaster, Eupolygaster, Desmogaster
and Drawida, the majority belonging to the last-
named genus.

This quarter of the globe is therefore inhabited
by 18 genera which are certainly truly endemic, and
which comprise between them about 120 species.
But only four or five genera are peculiar.

The remainder of the Asiatic Continent is not
very well explored with regard to its earthworm
inhabitants. It seems clear however that the southern
and coastal region of China and Japan with the Malay
peninsula are really continuous with the mass of
islands which lie between India and Australia and
form together a tract of land which is characterised
by an Oligochaetous fauna differing from both that
of India on the one hand and Australia on the other.

B. E. 6

82 EARTHWORMS AND THEIR ALLIES [cH.

We shall therefore consider this huge portion of the
globe as one region comparable to the other divisions
that have been hitherto considered. With reference
to the Lumbricidae and Geoscolecidae the same
remarks may be made as in the case of India.
The indigenous forms of the latter family are
to be looked upon as outside of the present survey
since they are largely or entirely aquatic forms.
Pontoscolex corethrurus, and Hudrilus eugeniae, need
not detain us for reasons already amply stated. We
now come to the great family Megascolecidae. Of
this family the genus Pheretima stands at the head ;
and of the 200 or so species that have been or can
be assigned to this genus all, with merely two or three
exceptions, are natives of the Eastern Archipelago
and adjoining mainlands of Asia. Of other Mega-
scolecinae the region has yielded the following genera.
In Java one species of Woodwardia (W. javanica) has
lately been described. It is regarded by Michaelsen
however as doubtfully indigenous. And the same
remark may be made of Perionyx. Plionogaster,
however, with four or five species, is limited, as far
as our present knowledge goes, to the Philippines and
to neighbouring islands. The Acanthodrilinae and
Octochaetinae are totally absent from this part of the
world, there being no record even of peregrine species
of these sub-families. The sub-family Trigastrinae is
not however unrepresented ; for of Dichogaster several

v] RELATIVE FREQUENCY 83

species occur, such as D. malayana and D. saliens.:
But these are by no means certainly to be looked
upon as real natives.of the situations within this area
where they occur. This completes the scanty list of
genera found in the region under consideration ; for
one Moniligastrid (MW. barwelli) is hardly to be looked
upon as indigenous. We have therefore to record
here but five genera, of which only two are certainly
indigenous and probably also confined to the region ;
they contain between them certainly two hundred
species.

We next come to the Continent of Australia. The
earthworm fauna is again quite without Geoscolecidae
and of course Lumbricidae. As to the former there
are not even doubtful cases like Glyphidrilus of the
East; for we find only recorded Pontoscolex core-
thrurus, a species concerning whose extraordinary
powers of migration there is no possible doubt. The
same may be said of Hudrilus also recorded from
Australia. Here the Megascolecidae are as conspicuous
as in the old world generally. We find, however, a
great manymembers of thesub-family Acanthodrilinae.
Of the antarctic genus Notiodrilus there are some
six species. Microscolex occurs; but the real habitat
of this genus is very doubtful. Diplotrema, with one
species, D. fragilis, is not only indigenous to, but
confined to, Australia.

The most prevalent sub-family is that of the

6-—2

84 EARTHWORMS AND THEIR ALLIES [cu.

Megascolecinae. Of the genus Pheretima there are
two species which may or may not be truly indigenous.
Of Plutellus there are forty species ; there are over
thirty of Diporochaeta, while Notoscolex (with which
Dr Michaelsen associates Digaster, Didymogaster,
Perissogaster) includes more than forty species,
Fletcherodrilus has but one species, Megascolex has
seventy species, Woodwardia sixteen, Spenceriella
five, and Megascolides seventeen. There are four
species of Pertonyx which were at one time regarded
by Michaelsen as necessitating a new but allied genus
Perionychella; the two are now merged. Thus there
are not far short of 150 species and eleven genera
represented, of which only two are limited to
Australia.

Having completed the survey of the central and
southern land masses of the globe we next direct
attention to the northern land masses, viz. North
and Central America on the one hand, and Europe
and northern Asia on the other. With regard to
America we find besides many species of Lumbri-
cidae the genera Notiodrilus, Microscolex among
the Acanthodrilinae, Megascolides and Plutellus of
the Megascolecinae, no member at all of the Octo-
chaetinae, a considerable number of species of
Ocnerodrilus and sub-genera belonging to the Ocnero-
drilinae, a good many species of Dichogaster and at
least one of T'rigaster among the Trigastrinae, while

Vv] RELATIVE FREQUENCY 85

one sub-family, that of the Diplocardiinae, is only
found here and contains two genera Diplocardia
and Zapotecia with quite ten species between them
of which only one belongs to the last-named genus.
There are no Geoscolecids (except the chiefly aquatic
Sparganophilus); this family stops short in the West
Indies where their presence has been briefly referred
to in considering the worms of South America. The
vast majority of the genera enumerated here are
only found in the warmer parts of the North American
continent. We have therefore in this division of the
world some nine genera of which at least one, viz.
Diplocardia (and its close ally, hardly perhaps to
be separated, Zapotecia), is confined to it, while
Trigaster only extends as far south as to the West
Indies.

Europe and northern Asia, of which Europe
alone and certain limited tracts of Asia are at all
known, contain all the genera of the family Lumbri-
cidae which are (according to Michaelsen) Hisenzella,
Eisenia, Helodrilus, Octolasium, Lumbricus with
various sub-genera of Helodrilus, such as Dendro-
baena and Allolobophora. Besides these forms,
which amount to at least 130 species, we find the
genus Hormogaster, with two species, the only genus
of the Geoscolecid sub-family Hormogastrinae; there
is also a species apiece of the genera Criodrilus
and Sparganophilus (sub-family Criodrilinae). But

86 EARTHWORMS AND THEIR ALLIES [cn.

as these are at least largely aquatic they come
under another set of rules and are not important in
the present survey of the earthworms of the world.
It will be thus seen that with these two last excep-
tions the area in question contains but six genera of
which all are peculiar.

We have now completed the survey of the prin-
cipal land-masses of the globe. We shall conclude
with a reference to one of the largest islands of the
world, viz. New Zealand, with which will be included
a few outlying islands such as the Aucklands, Snares
Island, etc. The reason for not ignoring these
islands as we have ignored certain other islands of
large size, such as Japan, will be apparent from the
peculiarity of the earthworm fauna which they
show. From New Zealand the Moniligastridae,
Geoscolecidae, Lumbricidae, and, of course, the
Eudrilidae, are absent, save the ubiquitous Hudrilus.
The only family of earthworms which is here repre-
sented is that of the Megascolecidae. Of this family
the Acanthodrilinae are very well represented. We
have at any rate seven species of the genus Notio-
drilus of which the bulk are from the small adjacent
islands and not from the mainland. The genus
Rhododrilus with nine species is actually limited to
the New Zealand group and so is an allied genus
consisting of two species only, viz. Leptodrilus. This
latter genus is confined, so far as present information

vi RELATIVE FREQUENCY 87

goes, to the Auckland and Campbell islands. Dino-
driloides with two species is also limited to New
Zealand and to the North Island. Maoridrilus with
some ten species is another native and _ restricted
genus. So too is the allied Plagiochaeta with
numerous setae on each segment but with the
alternating and single nephridial pores of Maoridrilus.
There are several species of Plagiochaeta of which
one has been lately regarded by Dr Michaelsen as
really falling within the otherwise Indian genus
Hoplochaetella, while for another he has formed the
genus Pereiodrilus. Neodrilus with but one species
N. monocystis is another peculiar New Zealand genus.
The family Octochaetinae contains only four genera,
of which one, viz. Dinodrilus (with four species), is
limited to New Zealand, while Octochaetus has about
five representatives. Hoplochaetella (if Dr Michael-
sen’s surmise referred to above be correct) has one
species in New Zealand. The Megascolecinae are
less numerous than the Acanthodrilinac, but there are
ten species of the genus Wegascolides (which includes
Benham’s genus J'okea), perhaps seven species of
Diporochaeta, and two other species which Michael-
sen, has removed from the genus Diporochaeta and
placed in Spenceriella. One Plutellus (which how-
ever may have been introduced) completes the New
Zealand Megascolecines. We have therefore in this
part of the world fifteen genera including between

88 EARTHWORMS AND THEIR ALLIES [cuH.

them some 58 species; eight of the genera are
peculiar to the islands.

From this brief statement of facts some inferences
of interest can be drawn. It is in the first place plain
that every part of the world except the extreme north
and south has a considerable fauna of earthworms. The
one exception would appear to be the northern part of
the North American continent. Here we meet with
members of the family Lumbricidae which are however
species that are met with in the Euro-Asiatic province
and are thus to be regarded as possibly later immi-
grants introduced probably byman. Thus temperature
short of a constantly frozen condition of the ground
is not a bar to the existence of earthworms. Kven a
freezing of the ground for lengthy periods is not
a complete obstacle to the existence of those Annelids ;
for I have myself received examples of Lumbricidae
from the arctic island of Kolguev. Moreover the
temperate regions would seem to be as fully popu-
lated in the way of individuals, and even of species,
as are the tropical regions. Indeed as to individuals
it seems that the temperate regions are more fully
supplied than much of the tropics. This however is
not quite the object of the present section to discuss.
We are here concerned with the relative frequency
of genera and species. There are according to a
recent estimate of the Rev. H. Friend some forty
species recognisable in Great Britain. And as already

v| RELATIVE FREQUENCY 89

has been stated the earthworms of EKurope amount
to perhaps 130,—at any rate well over one hundred.
In tropical America there are hardly more. But in
the latter case the number of genera is very greatly
in excess of that of Europe. We cannot however say
that an abundance of generic types is quite charac-
teristic of the tropics. For the Eastern Archipelago,
though rich in species, is but poor in genera, not
possessing more than half a dozen or so. And on
the other hand the temperate climate of New Zealand
has produced a very considerable series of genera,
much more than those of the islands of the East
and nearly as many as those of, for instance, Central
America and the West Indies.

This conclusion is in its turn contradicted by
the conditions observable in Chili and the temperate
regions of South America, where the number of
species is large but the number of genera small.
In short no general laws, in the present state of our
knowledge, can be laid down as to the connection
between species and genera on the one hand and
climatic conditions on the other. In this department
of our subject we cannot do more than has already
been done, #¢. to state the actual facts. One is
tempted in comparing the rich fauna of tropical
Africa with the very limited fauna of Madagascar
to associate a richness of types with extent of land
surface. In the two cases cited this conclusion is

90 EARTHWORMS AND THEIR ALLIES [cu.

obvious. It may also be extended—if we confine
ourselves to species and not to genera. For the two
great islands of New Zealand have not between them
more than fifty species of earthworms, while Australia
has four or five times that number. It will be noticed
however that we cannot associate poverty of generic
differentiation with limited land masses; for New
Zealand has a large number of generic types, very

many more than the huge Euro-Asiatic tract of
continent.

THE RANGE OF GENERA.

We have seen, and shall again refer to the fact,
that individual species of earthworms have not as
a rule a range over a great extent of country, save
only in those cases such as Pheretima heterochaeta
which belong to that physiological section of these
worms called ‘peregrine’ forms; these appear to
possess some means of extending their range by the
assistance of man which is denied to other forms.
Apart from these instances, which do not come under
the present category, it is only Lwmbricus and its
immediate allies, Helodrilus, etc., of which certain
species are found to exist over wide tracts of land.
There are however many genera which have a wide
range and which may be contrasted with others in
which the range is very limited. The two extremes

v| RELATIVE FREQUENCY 91

are moreover connected by forms with an intermediate
range. There is no doubt whatever that the genus
with the widest range is Notiodridlus of which species
are found throughout the antarctic region, viz., in
Patagonia, the islands of the Antarctic Ocean, the
Cape of Good Hope, New Zealand, and also further
to the north, sometimes even to and beyond the
tropics in America, Australia, and Africa. There is
no other genus of which the genuine extension
(ae. not in any way due to man) is so great as this
genus Notiodrilus. And this fact gains much signi-
ficance from the now generally accepted view that
in its anatomical structure Notiodrilus comes near
to the original type of earthworm.

Perhaps the next most widely distributed genus
is Helodrilus of the family Lumbricidae which oc-
cupies Europe and Asia to the extreme east, and is
thought also to be indigenous to certain parts of
North America. But this range, though equally wide
perhaps in mileage, is less impressive than that of
Notiodrilus, since the land areas inhabited by the
genus are continuous—almost so if we accept North
America as its real habitat. Here we have a case
precisely the opposite of that of Notiodrilus ; for
while there are reasons for regarding Notiodrilus as
an ancient form of Lumbricid, there are equally good
reasons for regarding the Lumbricidae as the most
modern family of earthworms.

92 EARTHWORMS AND THEIR ALLIES [cu.

To find other instances of widely spread genera
we must recur to the great family Megascolecidae.
There are practically no Geoscolecidae which have
a really extensive range. The only instances are
Criodrilus and its ally Sparganophilus which occur
in America, whether North or South, and in Europe ;
but as these forms are at least largely aquatic the
facts are not quite comparable with those now under
consideration.

The genus Dichogaster (which includes as synonyms
Benhamia, Millsonia, Microdrilus) is unquestionably
indigenous to tropical Africa and certain parts of
America including the West Indies. It has been
also met with in the East; but as the species there
occurring, such as for example the species originally
described by myself as Microdrilus saliens, are of
small size, an accidental introduction is quite possible,
and it is by no means certain that it has not occurred.
In any case the genus is known to possess species
which are undoubtedly to be reckoned among pere-
grine forms—such as D. bolavi, which has turned up
in Europe. Gordiodrilus and also Ocnerodrilus with
its sub-genera have very much the same range as has
Dichogaster. It is to be noted however that these
forms are circumtropical, and that their distribution
is thus less continuous than that of Notiodrilus ; they
do not however show the markedly discontinuous
range of certain other genera of Megascolecidae. For

v| RELATIVE FREQUENCY 93

instance Octochaetus is well known from New Zealand,
and, not occurring in the intermediate tracts, is again
met with in India. Hoplochaetella is believed by
Michaelsen to present us with another precisely
similar instance. Then also the genera Woodwardia
and Notoscolex are to be found in Australia and again
(absent from the immense tract lying in between)
in Ceylon. Megascolex has much the same range,
showing also this marked and remarkable discon-
tinuity. Stranger still, perhaps, is the range of
Plutellus and Megascolides, of which the former,
chiefly found in Australia and Tasmania, not only
extends its habitat to Ceylon but also to North
America; it is there represented by Eisen’s species
Argilophilus marmoratus, referred by him, and not
unnaturally, to a distinct genus, but placed by
Michaelsen in Plutellus. Megascolides is Australian
and from the North Island of New Zealand, where
its species were regarded by Benham as of a distinct
genus, Tokea. There is also one form, Megascolides
americanus, in the western region of North America.

The two genera Yagansia and Chilota, closely
related to Notiodrilus, have a range which is short
of that of Notiodrilus, and we shall see later that
there are reasons for regarding these genera as
derived from Notiodrilus. They are met with only
in the south of South America, and in the Cape of
Good Hope region.

94. KARTHWORMS AND THEIR ALLIES [cu.

The range of Microscolex seems to be much the
same as that of Notiodrilus; but it is a little uncertain
how far the genus is really autochthonous in the
countries where it occurs ; and in any case it differs
from Notiodrilus in occurring in Europe, where the
species has been named for a long time MW. phosphoreus.
We do not positively know whether this is ‘ peregrine’
in Europe or not.

The range of the antarctic Acanthodrilinae is in
a sense continuous; for they argue the former north-
ward extension of the antarctic continent and in any
case they occupy neighbouring land masses. In
Octochaetus and Plutellus the case is different and
one of real discontinuity. There are however cases
of wide range which is also actually continuous and
such is afforded by the genus Pheretima. This genus
appears to be possibly indigenous to Australia; in
any case it reaches from the Solomon Islands on the
east to India towards the west, being found in all
intermediate continents, while it reaches Japan on
the north side of this large area.

There are other genera which extend their range
over a considerable area, but which are not so
widely distributed as these which we have just been
considering. Thus Diporochaeta is chiefly Australian
but also reaches even the South Island of New Zealand
and the southward. lying antarctic islands. Desmo-
gaster and Eupolygaster among the Moniligastridae

v] RELATIVE FREQUENCY 95

range from Burmah in the east to Sumatra and
Borneo further east, though they are not recorded
from intermediate islands. Pertonya is found in
Burmah, India, Zanzibar, Sumatra, and Java. There
are other examples of genera which have much the
same range as those enumerated. Finally there are
those which are confined to one land mass and very
often to a restricted region of that. Thus Aynotus
is confined to Madagascar, all the genera of Eudrilidae
to tropical Africa, some of them, e.g. Beddardiella
and Huscolex, to very limited tracts, others to wider
or less wide areas in that continent. Maoridrilus is
only found in New Zealand, to the South Island of
which also is confined the genus Neodrilus. To the
Cape region of Africa is limited Wicrochaetus; and
to a belt running across the northern part of the
tropical region and extending down the Nile, the
remarkable, partly aquatic, Alma.

As a kind of appendix to these facts and con-
clusions we shall next deal with certain widely spread
forms that have been already referred to, with the
range of different genera over great land masses of
the world, and with the earthworms of oceanic islands.

96 EARTHWORMS AND THEIR ALLIES [cu.

CHAPTER VI
PEREGRINE FORMS

Dr MICcHAELSEN has used this term to describe
those species which possess some powers of migration
over the sea, denied to the majority of worms, and
probably due to the direct interference of man. Thus
we find in collections of earthworms from various
parts of the world not only examples of forms which
do not come from other parts of the world, but also
a few which occur in many or even most of such
collections. It is for example to be actually expected
that a collection of earthworms madeinSouth America,
the Philippine Islands, or Australia will contain ex-
amples of the apparently ubiquitous Pontoscolex
corethrurus. This is what has actually happened in
cases of which I have personal knowledge, as well as
in many others recorded in the literature of the
subject. I have myself received this worm from the
three parts of the world mentioned, and also from
Hawaii. Others have increased its known range to
other parts of the South American continent, to
Central America, the West. Indies, the islands of
Sumatra, Java, Borneo, Celebes, Mauritius, and
Madagascar, etc. It is in fact found everywhere in

vi] PEREGRINE FORMS 97

the tropics. With this range may be contrasted that
of another genus of the same family (Geoscolecidae),
viz. Kynotus, which, though consisting of many species,
is not found outside of the Madagascar district. It
should be added that Pontoscolex does not appear
to contain more than two species, the one not men-
tioned in the above survey of its distribution being
P. insignis of Kinberg, which is apparently the same
as P. liljeborgi of Eisen, and is limited to certain
parts of America.

Before attempting to grapple with the remarkable
facts implied by the distribution of this genus, it
will be well to survey the whole group of Oligochaeta
and to reduce to as short a space as possible the
total series of facts which are of the same nature.

A case, even more striking than that of Ponto-
scolex, is afforded by the Eudrilid genus Hudrilus.
As with Pontoscolex there are two species of this
genus, one, 2. pallidus, being confined to West Africa,
the remaining one, H. ewgeniae, being world-wide in
range. This latter species has received the following
names, viz. H. decipiens, E. lacazii, EB. peregrinus,
E. sylvicola, E. boyeri, BE. jullient, EB. erudiens, and
E. roseus; they appear to be all synonyms of the
name originally given by Kinberg who however did
not recognise the distinctness of the form as a genus.
It is now known as Ludrilus eugeniae. The variety
of names given to supposed different forms (for two

B. E. ii

98 EARTHWORMS AND THEIR ALLIES [cn.

of which I am myself responsible) is due to the fact
that in earlier days when nothing was known about
the geographical distribution of this group of animals
it was thought by no means unreasonable that a
given genus represented by several species should
range over the globe. This fact coupled with im-
perfect description of structural details led to the
multiplication of supposed species, a position which
is no longer tenable. This worm is quite as abundant
in gatherings from all parts of the world as is Ponto-
scolex corethrurus; and in addition to the countries
inhabited by the latter, Hudrilus ewgeniae has been
met with in New Caledonia: tropical Africa is
probably its original home.

The two families that have been hitherto considered
offer no further instances, among their many species,
of worms with so wide a range as those just dealt
with. There are indeed one or two forms, e.g. Crio-
drilus and Glyphidrilus, which have a considerable
range though not nearly equalling that of Hudrilus
and Pontoscolex.’ These are, however, aquatic forms
and the range of aquatic forms is determined as far
as we can see by a different series of causes to that
of terrestrial forms, which are referred to later.

Among the Moniligastridae we have apparently
an instance of a peregrine form. The genus itself
has its headquarters in Ceylon and extends a little
way in other eastern regions; there is, however, one

v1| PEREGRINE FORMS 99

species, Moniligaster bahamenis, described some
years since from the Bahamas which must surely
be an example of a peregrine form, particularly since
it is probably identical with M. japonicus whose
name is indicative of its habitat.

Among the huge family of the Megascolecidae
there are a considerable number of species which
apparently possess the same facilities for making
their way in different directions and across seas from
the locality that is thought to be their real home.

Of the very many genera, however, of which this
family is composed, a comparatively small number
are thus peregrine in habit at times. All the species
known which are distributed broadcast, more or less,
over the tropics belong to the genera Pheretima,
Microscolex, Dichogaster, Megascolex, Perionyx,
Ocnerodrilus, Kerria. These several genera are
placed in order of frequency of exotic occurrence.
Indeed of the two latter genera their frequent life
in fresh water may really remove them from the
present category altogether. In addition to these
are some perhaps more questionable instances, such
as the genus Gordiodrilus which, prevalently West
African, has also been found in the West Indies, in
Kast Africa, and in India and Madagascar. These
instances I propose to leave out of consideration in
the present sketch. The most obviously peregrine
genus of all those enumerated is Pheretima, which

7 ~»)

100 EARTHWORMS AND THEIR ALLIES [cu.

according to my experience turns up in almost all
gatherings of earthworms from any part of the
tropical or even sometimes temperate regions of the
world. It seems to be fairly well settled that this
extensive genus has its real home in the islands of
the Eastern Archipelago, perhaps extending a little
in various directions from that centre. But examples
of the genus have been found in almost all other
regions. And what is especially to the point in
considering the facts, as will be pointed out with
more emphasis later, the assumedly peregrine species
do not differ from those found in the real district in
which the genus is indigenous.

Dr Cognetti de Martiis enumerates in the Neo-
tropical region, that is in South and Central America
and the West Indies, the following species: Phere-
tema biserialis, P. californica, P. capensis, P. elon-
gata, P. hawayana, P. hesperidum, P. heterochaeta,
P. howlleti, P.posthumna, P. rodericensis, P. schmardae
and P. violacea. Of these twelve species it is quite
certain that the last six occur in the East, where
they are doubtless indigenous. So too do the species
P. biserialis, P. capensis, and P. hawayana. The
synonymy of the different species of this large genus
is not yet in a completely settled condition. But
in the meantime it is in my opinion quite possible
that both P. hespertdum and P. californica are
identical with species also occurring in the East.

VI] PEREGRINE FORMS 101

There remains the somewhat doubtful P. elongata from
Peru which has not been very fully described. There
is thus no convincing evidence of species really indi-
genous to and confined to any part of America. Some
of these species also occur in many other parts of the
world. For instance, P. heterochaeta is very widely
spread indeed, occurring as it does in Australia, New
Caledonia, Madagascar, and even England (in hot-
houses). This species indeed is the most prevalent
of all Pheretimas and seems to be abundant in
gatherings of earthworms from various localities as
are Hudrilus and Pontoscolex.

From the island of Madagascar and neighbouring
islands the following species of Pheretima have been
obtained and identified by Dr Michaelsen: viz.
Pheretima pentacystis, P.peregrinus, P. heterochaeta,
P. bisertalis, P. rodericensis, P. houlleti, P. robusta,
P. mauritiana, P. taprobanae, and P. voeltzkovi. 1t
will be noticed that the majority of these are also in-
cluded in the list from South America, and that many
of them are also found in other parts of the world, and
nearly all of them in the East. There remain a few
which are doubtful. It is quite possible that P. mazi-
tiana is the same as P. hawayana and P. bermudensis,
in which case it has a world-wide range. P. tapro-
banae is well known asa Ceylon species. P. robusta
also occurs in the East Indian islands. There remain
P. pentacystis, P. peregrinus, and P. voeltzkovi.

102 EARTHWORMS AND THEIR ALLIES [cH.

P. peregrinus is known from Australia and also from
Sumatra, so that that species need not concern us
in enumerating those which are possibly endemic.
In fact it is only P. pentacystis and P. voeltzkovi
which may be really Mascarene.

Another peregrine genus belonging to the sub-
family Acanthodrilinae is Wicroscolex. But the limits
of this genus may be regarded as at present rather
uncertain. And this difficulty somewhat affects the
bearing of the facts to be related, though it hardly
affects the value of the facts themselves. Dr Michael-
sen referred to the genus in his great work seven
well-defined species, and four others not so plainly
distinct. Of these eleven, two are confined to New
Zealand, four to North and Central America, one to
Hawaii, one to Madeira, one to Algeria, while the
remaining two are found pretty well over the whole
surface of the world. More recently the same
authority has somewhat extended his view of the
generic characters, so as to include a number of
forms found in Patagonia, Cape of Good Hope, and
the antarctic region generally, while he has lumped
together into two species only, viz. WM. phosphoreus
and M. dubius, the eleven forms just mentioned,
which species therefore are absolutely world-wide
in range, and thus form an excellent example of a
peregrine form. These species moreover differ from
Pontoscolex and some others in that they have been

VI] PEREGRINE FORMS 103

able to establish themselves in Europe. Dr Michael-
sen also relates that in the cultivated lands of South
West Australia, Microscolex dubius and Helodrilus
caliginosus are actually the commonest species; and
he calculates that they form together quite 90°/, of
the earthworms gathered in any locality belonging to
this region.

Some of the other Megascolecid peregrine forms
will be referred to later. There is no doubt that the
family Lumbricidae offers by far the greatest number
of peregrine forms and that these are most abundant
in collections from extra-European countries, where
the collector has searched in cultivated lands. There
are at least eight or nine species which are common
in many parts of the world though their original home
is undoubtedly Kurope.

This is a brief review of the facts, more detailed
in some cases than in others. It remains to review
and compare the results arrived at.

The first general statement that may be made is
that this faculty of extending their range beyond the
limits assigned by nature is not confined to any one
family. For all the chief sub-divisions of the terres-
trial Oligochaeta seem to possess it, though in unequal
degrees. But the inequality may be more apparent
than real. For if it be recollected that the species
of the family Megascolecidae are very much more
numerous than those of the Kudrilidae or even the

104 EARTHWORMS AND THEIR ALLIES [cuH. |

Geoscolecidae, the fact that there are more peregrine
Megascolecidae will lose some of its importance.
With the Lumbricidae the case seems to me to be
different. Here the preponderance, not only in species
(relatively speaking) but in individuals, is much above
that of other families. This preponderance I should
be disposed to assign to the newness of the family
coupled with the vigour seen in new races. That
this is a possible explanation is borne out by
the fact that the ‘Perichaetidae’ (ze. the genus
Pheretima) is the most salient race of peregrine
Megascolecidae, and it is now generally held that
this group is the most modern of that enormous
family.

Another general statement may be made with
even more confidence, viz. that it appears to be an
undoubted fact that some species are more capable
of extending themselves than others. Thus Hudrilus
cugeniae occurs everywhere on the great land masses
of the globe, except in Europe; it is in fact circum-
mundane in the tropical zone, as is also Pontoscolex.
Dichogaster bolavi is again a trifle more restricted
in its range, having been recorded from tropical
Africa, South America, West Indies, Madagascar, and
India. Its occurrence near Hamburg in Europe is
also to be noted. A little more restricted still is
Nematogenia panamaensis whose range is in Central
America, tropical West Africa, and Ceylon. Lastly

vi] PEREGRINE FORMS 105

there are cases such as Pheretima taprobanae which,
a native of Ceylon, is also found in Madagascar.

It may be asserted in the third place that there
are no peculiarities of structure shared by all of
these peregrine forms which might account for their
physiological similarity, except indeed the somewhat
negative feature which they have in common, that is
of being of small or moderate size. Hudrilus and
Pontoscolex are not isolated types in their respective
families; nor do they seem to approach each other in
any respect. Nor can it fairly be said that these
peregrine species are marked by any great variability
of structure as compared with other forms, which might
allow for their suiting themselves to various climates
and conditions. It is true that Hudrilus eugeniae has
received many names which might at first argue
some variability. But these names have been perhaps
given by persons rather under the influence of the
idea that remote habitat implied specific difference,
and who were thus inclined to see minute differences,
and who perhaps were furthermore led astray in the
matter by imperfectly accurate descriptions on the
part of others. Certainly some of the peregrine
species of Pheretima are subject to some variation,
particularly in the number and arrangement of their
genital pupillae. But this feature is by no means
confined to those species and cannot be utilised as
in any way an adaptation to wide distribution.

106 EARTHWORMS AND THEIR ALLIES [cn.

But while we can lay down no general explanation
of the phenomenon, it is possible to furnish some
explanation of particular cases. Thus the genus
Microscolex is the only exotic genus which appears
to have established itself in Europe, from which
country indeed it was early known as an apparently
indigenous inhabitant. We must put this and some
similar cases down to ability to do without great
heat. It is probable in fact that the original home
of Microscolex is the antarctic half of the globe; and
this of itself would allow of its establishing a new
home in the northern hemisphere, did other circum-
stances allow of it.

It might be urged that this genus has been able
to establish itself in Europe because it has in fact
had the chance denied to other species. There are
a good many, however, which would in that case be
in the same category. Some years ago I received
from time to time a very large number of earthworms
from the Royal Gardens at Kew which had been
accidentally imported thither from many quarters
of the globe, among which I described some eighteen
or twenty new species including, for instance, the
African genus Gordiodrilus. There are plenty of
facts of a similar nature and Dr Michaelsen has
pointed out that botanical gardens act as centres
of dispersion for accidentally introduced Oligochaeta.
We must therefore come to the conclusion that

vI] PEREGRINE FORMS 107

temperature is at least one of the causes of a
difference in the capability of extending their range
shown by the Oligochaeta, a cause which doubtless
operates as a check upon extension of range in non-
peregrine forms also, and prevents for instance the
dispersion of the tropical African Eudrilidae into the
region of the Cape.

We may, as it appears to me, confidently look
upon indifference to varying temperature as a con-
dition of ability to colonise new countries. But it
is obvious that this is not of itself a sufficient cause
to explain the facts. Otherwise this country and
N. Europe would contain many antarctic earthworms ;
the only one that has been recorded to my knowledge
is Microscolex.

Though an inability to endure a temperate climate
may have rendered the movements of peregrine
species more limited, the same or rather the exactly
opposite cause does not seem to have played any
important part in this direction. For it is above all
the Lumbricidae, normally dwellers in temperate
climates, that are so remarkable for their wide range
over the world. Nor can it be convincingly asserted
that the extra-Palaearctic Lumbricids are real in-
digenes of those—often tropical—countries. For if so
we shouldexpect them to be at least of different species.
Lumbricids however from South America, Australia,
etc., are specifically identical with Kuropean forms.

108 EARTHWORMS AND THEIR ALLIES [cH.

There is no doubt that wherever land has been
at all long under cultivation in any part of the world
that land will be found to produce species of the
European genera Lumbricus, Helodrilus, Eisenia, ete.
More than this the recently imported European forms
will be found to have largely or almost entirely driven
out the native species, which have retired more into
the interior of the country. There is thus here no
barrier placed by temperature. It should be remarked,
however, that while these earthworms are most abun-
dant in the less tropical regions, they occur in such
tropical districts as Peru, though in less striking
numbers. Whether those of North America are really
indigenes or not remains perhaps a matter for dis-
cussion; but it is at least noteworthy that the vast
preponderance of species occurring there are alse
European and even British. In this particular case,
which is on the whole the most emphatic of all the
cases of peregrine earthworms, some explanations
are possible, or at least have been offered. In the
first place it would appear that earthworms are more
abundant as individuals in northern countries where
the soil is rarely dry for prolonged periods. And as
has been already pointed out there is a close relation
between earthworms and agriculture. Dunghills are
fertile gathering grounds for some species, and
ploughed fields and gardens always swarm with
several species. In the tropics these animals are

vit] EARTHWORMS OF OCEANIC ISLANDS 109

not so evident; and the strong rays of the sun
appear to drive them further underground and into
marshes; this obviously lessens the chance of their
accidental transference by man. Furthermore
Dr Eisen has pointed out that the European species
are apt to have clitella and to be fertile all the
year round, which is not always the case with other
genera. That naturalist has added to this observation
the fact that in rich cultivated soils in California it is
impossible to find anything but imported European
species, since cultivation itself appears actually to
drive away the native forms.

CHAPTER VII
THE EARTHWORMS OF OCEANIC ISLANDS

OCEANIC islands are islands that have always been
islands, a definition that seems tautological until we
compare it with some other land masses that may be
termed ‘islands.’ Geology teaches us in fact that from
the point of view of their origin islands may be
divided into two quite sharply contrasted classes.
There are those detached land masses usually lying
near to or comparatively near to some continent,
which have been in the course of time detached by
the action of the waves from that continent, such

110 EARTHWORMS AND THEIR ALLIES [cu.

as for instance the British Isles, which undoubtedly
represent a portion of the European continent which
was once quite continuous with Europe. On the other
hand we have the Hawaiian archipelago, St Helena,
Fernando Noronha, and other similar islands, which
are more remote in their position from continents
and concerning which it seems clear that they have
originated de novo by the action of submarine
volcanos or of the growth of coral, combined with
subsidence, following elevation, or from several of
the causes combined. In any case the islands which
are termed oceanic islands have never formed part
of a continent. They are not relics of previously
existing continents. It becomes a matter of great
interest to compare the earthworms which are to be
found upon oceanic islands with those which inhabit
continental islands. Fortunately there are a good
many facts at our disposal for this purpose; and we
shall compare the earthworms of the Hawaiian
archipelago with those which are found upon certain
small islands lying to the south of New Zealand, viz.
Campbell and Auckland islands and the more
southern Macquarie islands.

The earthworms of the Hawaiian archipelago have
been studied by a good many persons, and altogether
a number of species have been described from that
group of islands of which the following is a list:
Pheretima hawayana, P. heterochaeta. P. peregrina,

vit] EARTHWORMS OF OCEANIC ISLANDS 111

P. schmardae, P. hesperidum, P. morrisi, P. per-
kinsi, P. biserialis (= P. elongata), Allolobophora
putris (=Kinberg’s Hypogacon havaicumn), A. foetida,
A. caliginosa, A. nordenshioldi, A. limicola, A. rosea,
and finally the well-known Pontoscolex corethrurus.
Of these species there is only one which is even
possibly a form limited to the Sandwich Islands, and
that is Pheretima perkinsi, a species which I myself
at first described as a new form, but which was after-
wards regarded as identical with P. heterochaeta by
Michaelsen, and later still resuscitated by Ude. All
the others are found in many parts of the world and
not only in the nearest mainland to the archipelago
which we are now considering. I have had already
occasion to speak of some of them as peregrine forms,
especially of Pontoscolex corethrurus which occurs
all over the world.

The conditions which have been recently revealed
by an exploration of the antarctic islands mentioned
above are totally different. Dr Benham has enu-
merated the following species from those islands, viz.
Notiodrilus haplocystis, N. fallax, N. aucklandicus,
N. campbellianus, N. macquariensis, Plagiochaeta
plunketi, Rhododrilus cockayni, Leptodrilus leptome-
rus, L. magneticus, Plutellus aucklandicus, Diporo-
chaeta heterochaeta, D. brachysoma, D. helophita,
D. perionychopsis among the Megascolecidae, besides
Phreodrilus campbellianus, Pelodrilus tuberculatus,

112 EARTHWORMS AND THEIR ALLIES [cu.

P. aucklandicus and the Lumbricid Helodrilus con-
_strictus. There were also four species of purely
aquatic Oligochaeta which we shall leave aside from
the present enumeration, as their range in space is
a matter requiring a different explanation from that
of the terrestrial forms. Here we have a series of
worms, all of which, save the widely spread Lumbricid,
are apparently absolutely indigenous to the islands
mentioned since they are all different as species from
those found elsewhere. Indeed there is a whole
genus Leptodrilus, consisting, it is true, of but two
species, which is a native of the Campbell and Auck-
land islands and of those only. The other genera are
found in the antarctic region, while Pelodrilus is
still more widely spread.

These facts as will be observed contrast about as
strongly as they can with those supplied by the fauna
of Honolulu and its adjacent islands. Not only are
the worms of the antarctic islands different species
from those found elsewhere, but the majority of them
do not consist of widely ranging peregrine forms. It
appears therefore most probable that these islands are
not oceanic islands but a portion of the former existing
northern portion of the antarctic continent. Were the
species identical with those of New Zealand _ this
conclusion would have of course to be reconsidered.
The barriers to migration (see chap. VIII) explain the
contrast recorded in the foregoing pages.

vul| MOVEMENT AND MIGRATION 113

CHAPTER VIII
MOVEMENT AND MIGRATION AMONG EARTHWORMS

THAT earthworms can move upon the surface of
the ground at a rapid pace is probably well enough
known to everyone, and that they can also burrow
with considerable celerity. Multiplying the inches of
progress in minutes of time by centuries with the
resulting miles, it is quite clear that there is no
reason to suppose that an individual earthworm
might not enormously extend its range under favour-
able circumstances. Their powers of locomotion are
such that they could in the course of comparatively
few centuries people a continent. As a matter of
fact these animals are frequently very widely spread
upon a given land surface; but on the other hand
they are sometimes equally limited. It behoves us
therefore to enquire the reasons for the possibility of
extended migration and the causes which have led to
its restriction. Weare now, it must be borne in mind,
considering these animals as purely terrestrial animals
moving over the surface of the land by their own
unaided efforts. We leave out of consideration any
possible assistance in crossing water, whether fresh
or salt. We have to consider in fact in the present

B. E. 8

114 EARTHWORMS AND THEIR ALLIES [cu.

section the earthworm inhabitants of larger and
smaller tracts of continuous land such as the African
continent, which will serve as an excellent example
wherewith to test the facts and inferences.

And asa ‘control’ we can compare this continent
with the very different continent of Europe.

As an excellent instance, because of the certitude
of specific and in most cases of generic distinctions,
we may take the Eudrilidae as illustrative of the
facts that are to be considered in the present section.
That family consists, as will be remembered, of 33
genera at most, which have the following more exact
range on the African continent. The genus Hudri-
loides occurs in British and German East Africa and
has been met with as far south as Mosambique and
even Durban, in which latter locality it has been
thought that it is really an accidentally introduced
stranger. Platydrilus is limited to eastern equatorial
Africa, thus not having quite the range of Hudri-
loides.

The small genera (that is small in numbers of
species) Reithrodrilus, Bogertia, Megachaetina, Meta-
drilus, Notykus have the same limitation of range as
the last genus. Metschaina has a wider range from
tropical North East to lake Tanganyika. Stuwhlmannia
has a wider range still being found as it is in the
Tanganyika district, in tropical North East Africa,
and in British and German East Africa near the

Vit | MOVEMENT AND MIGRATION RS

coast. Pareudrilus reaches still further north while
Nemertodrilus is limited to the Mosambique region
and to the Orange River district further south. The
only remaining genus of this sub-family of the
Eudrilidae is Libyodvilus which is purely West
African and equatorial.

Of the remaining genera which are usually grouped
together into a second sub-family, five, viz. Malo-
drilus, Kaffania, Gardullaria, Teleudrilus and
Teleutoreutus, are confined to tropical North East
Africa. Hminoscolex occurs in the same district but
also to the south in the great lake region. The most
remarkable fact about this genus is that one species
E. steindachneri comes from the Cameroons, and
another EH. congicus from the Congo, and thus the
range of the genus is right across the continent.
Neumanniella has much the same range. Poly-
toreutus is a purely equatorial East and Central genus,
reaching from the coast to the lakes. Bettonia known
by three species is from British Kast Africa.

The remaining genera, viz. Hyperiodrilus, Helio-
drilus, Alvania, Iridodrilus, Rosadrilus, Euscolex,
Parascolex, Preussiella, Buttneriodrilus, Beddard-
iella, Metascolex, are all West African and the vast
majority equatorial. We thus see that with one
exception the genera of Kast Africa are totally
different from those of West Africa and that the
family as a whole is restricted in its range to a

RQ ~»)

116 EARTHWORMS AND THEIR ALLIES [CuH.

comparatively small part of the vast African continent.
It also obviously follows, and it is advisable to state
this fact however obvious, that no species are common
to the two sides of the continent except indeed the
ubiquitous Hudrilus, whose range over the world has
been more than once referred to in this book.

On the other hand the genus Dichogaster offers
quite different facts, which are in contradiction to
those just enumerated. This genus as already said
is very characteristic of tropical Africa, and a large
preponderance of the known species are confined to
that continent. Although there is some variation in
structural characters among the many species which
compose this genus, there is but little doubt that
they are all rightly referred to one genus with
perhaps some doubtful, though not very striking,
exceptions. In any case the utmost divergence of
structure between worms usually placed together
in this genus is nowhere near to that which separates
the genera of Eudrilidae from each other. Of the
African members of the genus the species are pretty
evenly divided between the eastern and western
halves of the continent; they are, like the Eudrilidae,
tropical in range, not occurring to the southward,
where their place is taken by the Acanthodrilinae
and Geoscolecidae. There are it is true a few species,
such as D. gracilis and D. bolavi, which are common to
the two sides of Africa; but in these cases we clearly

VIIr| MOVEMENT AND MIGRATION 1g bre

have to do with those rather mysterious species
which can apparently unduly extend their range and
which are known as peregrine forms; for they also
occur in other parts of the world besides Africa. We
have therefore in Dichogaster the case of a genus
which ranges all over the tropical parts of Africa,
but whose species are not common to the Atlantic
and Indian shores of that continent.

We will now contrast these conditions, which
exemplify certain facts shown by the characteristic
Oligochaeta of tropical Africa, with those which
obtain in Europe. In this region of the world the
prevalent and practically the only genera which
need be taken into consideration in surveying the
Oligochaetous fauna from the present point of view,
are Lumbricus and the genus Allolobophora_ of
Kisen which has been variously rearranged into generz
and sub-genera known by the names of Helodrilus,
Bimastos, Octolasium, etc. The structural differences
which divide these genera and sub-genera are not
great; in any case they do not exhibit such a wide
range of variation from each other as do two such
Eudrilid genera as Stuhlmannia and Hyperiodrilus.
We find the genera mentioned not only in Kurope
but extending themselves over more or less of Asia,
even occurring in Japan; while the North American
continent contains also representatives of the same.
Not only do we find this community of genera over

118 EARTHWORMS AND THEIR ALLIES [cu.

vast extents of country greater in diameter than the
African continent, but there are also many species
which range as widely or nearly as widely as the
case may be as the genus to which they belong.
Thus the species of Allolobophora (we do not trouble
about the newer sub-divisions as they hardly affect
the facts to be emphasised), A. caliginosa, A. longa,
A. rubida, A. chlorotica, A. octaedra, A. constricta,
A. beddardi, Lumbricus terrestris, L. castaneus, have
an enormously wide range over what is generally
termed the Palaearctic region, extending also in some
cases into the Nearctic. It is true no doubt that the
majority, indeed perhaps all, of these are, like certain
species of Dichogaster mentioned above, among those
forms termed peregrine which have the capability of
living in every quarter of the globe to which they
have apparently been conveyed by man. But there
remain many species which have a very extended
habitat in the northern hemisphere, and in any case
the genera and the species are there truly indigenous
and widely spread.

It would thus appear that the capability for inde-
pendent migration varies greatly among earthworms.
Of the types selected for consideration the Eudrilidae
are the slowest movers ; the genus Dichogaster comes
next, while the power of migration possessed by the
genera Allolobophora and Lumbricus is very much
greater. Assuming for the moment the correctness

vu] MOVEMENT AND MIGRATION 119

of this inference it is clear that it will influence many
other propositions connected with the relative age
of the families of these worms and with many
problems of geographical distribution. It appears
to us that this simple explanation is the correct one.
But to show this it will be necessary to eliminate
other possible explanations. It might be urged that
the wider range of the genus Dichogaster and the
still wider range of the genus Allolobophora (shown
by community of species in widely distant localities)
was evidence merely of relative age, that the older
groups have had more time to travel and that the
newer groups have not had so long a time to spread
themselves over their habitat. On this hypothesis
the genera of Eudrilidae would be geologically much
newer than the genus Dichogaster and similar state-
ments .might be made for the other forms here
under consideration. As already explained we cannot
attempt to answer this question in the only way in
which it can be really satisfactorily answered, by a
reference to fossil forms; for there are no fossils to
refer to. So far as comparative anatomy enables us
to arrive towards a solution of the question, it would
appear that the genus Dichogaster belongs to a more
ancient race than either of the other two groups
considered, and that of these latter the Lumbricidae
are the most modern. Moreover we associate not
only a wide, but also a discontinuous, distribution

120 EARTHWORMS AND THEIR ALLIES [CH.

with an archaic race; and for this reason also we
should place the genus Dichogaster in the position of
being the most ancient of these Oligochaeta. For the
genus occurs in Central America and in certain parts
of the East as well as in Africa. So that we can
fairly dismiss the view that the Lumbricids by virtue
of their greater range over a given area are the most
ancient type and that their range is associated merely
with their antiquity. Nor does it appear that geo-
graphical or meteorological consideration can have
had effect in the present instances. For conditions
favourable to earthworms prevail in tropical Africa,
as in Europe and much of North Asia.

CLIMATE AS AFFECTING MIGRATION.

That excessively rigorous climatic conditions affect
the range of earthworms as well as fresh-water forms
is quite clear from the conditions which obtain in the
most northern climes. At any rate in those regions
where physical conditions render it impossible for
these Annelids to have their being. A perpetual
mantle of snow and a temperature far below freezing
point are absolute barriers to the extension of range.
And yet there are some few Oligochaeta which do
not in the least suffer from a somewhat milder taste
of such conditions. Thus species of Enchytraeidae
have been met with on glaciers and even found in

vilr| MOVEMENT AND MIGRATION 121

frozen water, while a few earthworms have been
brought from the island of Kolguev. These however
are quite exceptions to the general sterility as regards
earthworms of the excessively cold regions. We have
already seen that there are no general facts to be
deduced as concerning the relative abundance of
terrestrial worms in the tropics and in more temperate
climes. Tropical Africa is, it is true, rich in genera
and species; but on the other hand tropical East
Indies have but few genera inhabiting their numerous
islands. Temperate England has very few genera
and not a large number of species ; temperate New
Zealand has a considerable number of different in-
digenous genera. When however we leave this
general aspect of the question and consider separate
families and genera, there seems to be some little
relation between climate and distribution and thus
some effect of climate in acting as a barrier to migra-
tion. For example, though continuity of land surface
permits of the tropical African Eudrilidae ranging
southwards as far as the Cape they are not met with
so far as we know in the most southern parts of
Africa ; nor are the South American Geoscolecidae
found in Patagonia or northward beyond Central
America. These instances do really look like an
influence of climate upon range. On the other hand
we must be careful to eliminate the possibility of
another explanation and that is the impossibility of

122 EARTHWORMS AND THEIR ALLIES [cn.

successful migration owing to the previous occupa-
tion of the ground with abundant other forms. The
very same countries would appear to show that this
explanation is unnecessary. For the prevalent genus
of the southern tracts of South America Notiodrilus
extends its way northward as does the same genus
from temperate to tropical Africa and Madagascar.

It looks very much, therefore, as if certain Oligo-
chaeta are dependent upon climate for their range,
and as if others were at least more independent of
climatic conditions. And there are other facts which
support this view. The same opinion is supported
by the phenomena of involuntary migration, a subject
which has been considered also separately under the
head of ‘ Peregrine forms.’ The great prevalence of
Lumbricidae accidentally imported into many parts of
the world shows that temperature is no real bar to
their voluntary migration. On the other hand the fact
that specimens of the East Indian genus Pheretima
though commonly imported accidentally into the
warmer regions of the world have not been able to
make good a footing in Europe, save in greenhouses,
shows that this genus is affected in its range by
questions of climate. These facts suggest another
inference of great interest which can only be
mentioned tentatively, and not put forward as a
demonstrated conclusion. Seeing that Lumbricus
(sensu lato) can comfortably take up its home in

vir] MOVEMENT AND MIGRATION 123

warm extra-Huropean countries, but yet that it has
evidently not spread to those countries in the course
of nature but by man’s interference, it seems possible
that time alone has prevented this ; and that there-
fore this family Lumbricidae is one of the most
recently evolved families of Oligochaeta. Certain
structural features support this way of looking at the
matter. The same arguments precisely apply to the
genus Pheretima, which is also regarded by most
systematists as a recently developed race of earth-
worms. Anyhow the conclusion which the facts seem
to warrant is that the effects of climate in influencing
distribution are seen to have an unequal effect upon
earthworms, some genera being debarred by climatic
conditions while others are indifferent to the same.

MouUNTAIN RANGES AND THE MIGRATION
OF EARTHWORMS.

In many groups of animals the interposition of a
lofty chain of mountains presents an insuperable
barrier to migration. The barrier is effective for
more than one reason. Lack of vegetation and a
differing climate are among the more obvious causes
which render Alpine chains important as affecting
distribution. There is plenty of evidence in the way
of positive fact that mountains are not necessarily
barriers to the spread of earthworms. The recent

124 EKARTHWORMS AND THEIR ALLIES [cu.

explorations of the Ruwenzori chain of mountains
in Africa have resulted in the collection of a con-
siderable number of species, some of which come
from great altitudes (eg. 4000 metres and slightly
upwards), and one species, viz. Dichogaster duwonica,
which Dr. Cognetti de Martiis described from the
foot of the glacier Elena. I have in my temporary
possession a number of examples of the eastern genus
Pheretima, some of which are new species from lofty
areas in the Philippine Islands. There are plenty of
other examples pointing to a like conclusion. It is
noteworthy that these forms which have been met
with at lofty heights are not essentially different
from the plain living forms. One cannot exactly
speak, at any rate in the present state of our
knowledge, of anything like an Alpine fauna.

It is in fact clear enough that whatever may
prove to be the case with regard to particular species,
a mountain range is not necessarily a barrier to the
dispersal of generic types.

THE OCEAN AS A BARRIER TO MIGRATION.

It is very possible that further investigations into
the Oligochaeta will prove that there are more marine
forms than those which are enumerated in another
chapter. Particularly is this likely to be the case
among the family Tubificidae and Naididae. For up

vul| MOVEMENT AND MIGRATION 125

to the present those forms belonging to those families
which are known to be positively marine in their habit
show no great difference from allies inhabiting fresh
water, and are in one case indeed (Paranais) common
to fresh brackish and saline waters. As to earth-
worms, the number is also extremely limited, and
Pontodrilus is up to the present the only genus which
is known to inhabit a marine situation almost ex-
clusively. It has, moreover, been shown that both
earthworms and their cocoons are susceptible to salt
water and are killed thereby. Thus the facilities
which these animals possess of crossing tracts of ocean
are limited by this fact alone, besides other impedi-
ments offered by tracts of water as such. We may in
fact entirely discount the possibility of earthworms
floating across arms of the sea—of any extent at any
rate. For they do not swim or float, but sink in
water. Possibly when the alimentary tract was
entirely empty of earth the worms might float ; but
it is always full and even if evacuated during their
passage to the bottom waters the body thus freed
would hardly rise. However the noxious qualities of
sea water to earthworms is a sufficient barrier to their
traversing even narrow straits. On the other hand
it might be suggested that torn up trees especially
with the roots and clinging earth still attached might
harbour worms and thus transmit them to foreign
shores. It has been suggested that in this or

126 EARTHWORMS AND THEIR ALLIES [cu.

in some similar way the species of Notiodrilus have
been wafted from shore to shore of those lands which
are washed by the Antarctic Ocean. Dr Benham,
however, in criticising this, calls attention to the
violent gales and disturbances of the ocean surface
which are so prevalent in those stormy regions, and
doubts much whether these animals could retain a
safe hold upon some travelling tree trunk. Moreover
it is only in this antarctic region where the earthworm
fauna of the various continents and islands are so
very similar.

FACILITIES OF MIGRATION.

The above brief account of physical features which
affect the range in space of the terrestrial Oligochaeta
seem to show that the only really important barrier
is the ocean ; and even a narrow tract of sea water
would, as it appears, act fatally in preventing the
successful immigration of a race inhabiting one shore
to the opposite shore. On the other hand we do un-
doubtedly find in different countries—even when
separated by a large expanse of ocean—closely related
forms. The most striking instance of this is that
afforded by a consideration of the antarctic species
of Notiodrilus and Chilota. Can this interchange of
Oligochaetous faunas be explained by any means which
earthworms possess of crossing tracts of sea by the

VIII | MOVEMENT AND MIGRATION 127

aid of living carriers such as birds? It has been
definitely shown that these creatures actually do
convey such small animals as Mollusca attached to
their feet. Is anything of the kind likely in the case
of earthworms? In the first place it may be safely
asserted that if it be possible it has not been actually
proved. This however might be perhaps put down to
the lack of sufficient observation of actual birds and
the contents of such masses of soil as are found
attached to their feet. A consideration of the habits
of earthworms seems to imply that such a mode of
transference from country to country is unlikely. In
the first place we remark that the general behaviour
of earthworms renders this unlikely. Even the
smaller kinds, whose bulk would allow of their being
carried, are too active in their habits to permit of a
safe transference. When disturbed they wriggle and
progress with activity. It is not conceivable that
they would remain quiescent for sufficient time to
allow of a long voyage. But while the bodily trans-
ference of adult earthworms seems highly improbable
it is conceivable at the first view that their cocoons
might be so transferred. We require to know rather
more about the cocoons of earthworms before we can
accept this view as a possibility ; as far as our present
knowledge goes it is not likely that these animals can
be assisted to emigrate in this way.

For the cocoons are rather bulky for this kind of

128 EARTHWORMS AND THEIR ALLIES [cu.

porterage. Moreover they are apt to be deposited
rather deep down and among the roots of grasses, and
in situations where they are not so likely to become
entangled in the feet of drinking birds. Assuming,
however, that these difficulties can be got over there
remains another difficulty. A single cocoon among
the terrestrial Oligochaeta does not contain a large
number of embryos, as has been pointed out on a
previous page. It is true that Allolobophora foetida
has six within one cocoon, but most of our indigenous
forms have but from one to three embryos in a single
cocoon. Thus, if successfully imported, it is hardly
likely that the developed embryos scattered after their
emergence would come together for breeding purposes;
and in cocoons with but one embryo the accidental
importation in this way would have to be very frequent
to produce any result.

The case here is exactly the reverse of that afforded
by the aquatic families (or many of them). In these
Annelids the attachment of the cocoon to water plants,
which are liable to be entangled in the feet of shore-
frequenting birds, would tend to favour migration.
And in addition to this the cocoons are naturally
smaller and often contain a considerable number of
embryos. We are to note that the aquatic forms are
on the whole distinctly wider in their range than are
the earthworms.

Ix | GEOGRAPHICAL DISTRIBUTION 129

CHAPTER IX

THE GEOGRAPHICAL DISTRIBUTION OF
EARTHWORMS

THE facts referred to and considered in the last
chapter lead to further observations upon the geo-
graphical distribution of this group of animals and
suggest problems for solution,

It is not the place here to give a general sketch of
the division of Biology termed Zoogeography ; but a
few general conclusions must be laid before the reader
in order to render what follows intelligible. It is
universally agreed that the range in space (and in
time also) of a given species of animal (or plant) is
as much a part of its scientific definition as are its
anatomical characters. A description for instance of
Acanthodrilus ungulatus is incomplete without a
reference to the fact that it occurs in, and is confined
to, the island of New Caledonia.

Each continent or island or part of a continent
and part of an island has its own peculiar inhabitants
as well as some others which range beyond its confines.
Thus as we have seen the genus Hyperiodrilus is
confined to the tropical West of Africa while the
genus Dichogaster-also found in that region is also
met with in other parts of Africa as well as in certain

BE. 9

130 EARTHWORMS AND THEIR ALLIES [cu.

parts of America and of the East. In this way the
entire globe may be mapped out into regions charac-
terised by their inhabitants and these regions may
also be further subdivided. The commonly accepted
regions were originally devised by Mr Sclater and are
known as the Palaearctic, Nearctic, Neotropic, Ethio-
pian, Oriental (Mr Sclater’s name was ‘ Indian’), and
Australian. These regions were originally formed
to convey the facts relative to the distribution of
Passerine birds only; but it is generally held that
they apply also to the distribution of vertebrates
generally. The science of zoogeography does not
however end with the display of maps conveying
graphically the mere facts of distribution of this group
and that. Its business is also to enquire into the
causes of the affinities between the faunas of different
regions or the varying degree of remoteness which
those faunas may show. On the one hand the varying
powers of dispersal and the means of extending their
range possessed by different animals have to be con-
sidered, and on the other hand geological changes in
the relative position of land masses have to be taken
into account.

The specific identity between the earthworms of
Great Britain and the adjacent part of the continent
of Europe would be very difficult to understand were
we only acquainted with the fact that salt water is
fatal to these animals. But we also know from

Ix] GEOGRAPHICAL DISTRIBUTION 131

geology that it was only at a very recent date that
England was cut off from union with the continent.
Thus an identity of fauna was to be expected. On
the other hand we are confronted with a very great
difference between the earthworms of eastern tropical
Africa and of the adjacent island of Madagascar.
In the latter we have as a prevalent form the genus
Kynotus; in the former continent many Geoscolecidae
but no Kynotus. It is believed that the separation
of Madagascar from the mainland was at an earlier
date than that of Great Britain from Europe. We
must however be cautious before slipping into what
might seem a case of arguing in a circle. It will
however probably not be disputed that Madagascar
was severed earlier than England.

We will now attempt to map out the world into
a series of regions characterised by their earthworm
inhabitants and see how far these regions agree with
those rendered necessary by the distribution of some
other animals.

We can to begin with accept the Palaearctic
region. The region however will be a little different
from that usually accepted. For we must probably
exclude Japan, whose earthworm fauna contains the
characteristically Eastern genus Pheretima. Other-
wise we have a region characterised by the family
Lumbricidae, which is really limited to it, and by just
a few traces of other genera such as Hormogaster

9—2

132 EARTHWORMS AND THEIR ALLIES [cn

among the Geoscolecidae and Sparganophilus which
however is possibly an accidental immigrant. This
region is certainly quite clear. Now according to
some persons such as Prof. Heilprin the northern
part of America should be joined with Europe and
Asia to form an Holarctic region; while by most
authors, the separate name of Nearctic is given to
the north of the New World. With regard to the
terrestrial Oligochaeta it appears to me that this
part of the world is possibly to be excluded altogether
as possessing no indigenous worms.

In considering the distribution of the Mammalia
Sir Ray Lankester excluded New Zealand from his
view as never having possessed any indigenous mam-
malian fauna, and termed this part of the world
Atheriogaea. In the same way it is possible that the
northern part of the United States and Canada,
whose earthworm fauna consists of species of Lum-
bricidae identical with those of Europe, may possibly
be also a region to be excluded in the present survey
and spoken of as ‘ Ascolecogaea.’ In the southern
part of the United States we shall find genera which
will be considered presently. On the other hand it
is equally conceivable that this part of the world
lost its earthworm fauna through excessive glaciation
in the ice age, the forms having been driven south
and are now only gradually making their way north-
wards again. In this case the modern earthworm

Ex] GEOGRAPHICAL DISTRIBUTION 133

population which appears to be absent from large
tracts of Canada will be simply due to involuntary
migration. These two views must be left for further
development.

In any case the southern parts of the United
States seem to be separable as a distinct region
from South America and to be characterised by the
sub-family Diplocardiinae, the genus Diplocardia
extending as far northwards as the state of [linois.
The distinctness of such a region however from
Central America and the West Indies is marred by
the abundance of Ocnerodrilus of which Dr EKisen
has described so many forms. On the other hand
the West Indies are closely allied in their earthworm
fauna to tropical South America, sharing with that
region several forms of Geoscolecids belonging in
both cases invariably to the sub-family Geoscolecinae.
The bulk of the latter are undoubtedly tropical South
American in range and there is no doubt whatever
about the distinctness of this part of the world as a
separate region. There is moreover a further puzzle
which confronts us who are trying to delimit an
American region or regions. In North America are
species of the genus Argilophilus which is referred
by Michaelsen to the genus Plutellus which comes
from the East and at least one species of Megascolides,
also an Eastern genus.

There is at present no doubt to be thrown upon

134 EARTHWORMS AND THEIR ALLIES [cu.

the indigeneity of Plutellus. The species according
to Dr Eisen show every sign of being genuine in-
habitants of California and like certain New Zealand
species such as the Tokea esculenta of Benham
(referred by Michaelsen to the genus Megascolides)
were eaten by the natives. If these genera were
forms restricted to North America, that is not only
with reference to the rest of America but to the
world generally, there would be as I think no doubt
about the practicability of making a Nearctic region.
As it is, it seems to me to suit the facts of distribution
better to regard the whole of the land under con-
sideration as forming one great Neogaean region
with three sub-regions, the North American, Central
American and West Indian, and tropical South
American. This region however will not as I take
it include the southernmost extremity of South
America. Here in Patagonia and in neighbouring
islands we have a different earthworm fauna. It is in
fact characterised by the sub-family Acanthodrilinae
of which it is true some members of the genus Notio-
drilus extend further north. I shall however defer
this part of the subject until the more easy delimita-
tions of regions are disposed of.

Tropical Africa is evidently to be included in a
third region which will be defined by the Eudrilidae,
Microchaetinae among the Geoscolecidae, and by the
great prevalence of Dichogaster, a genus whose

Ix | GEOGRAPHICAL DISTRIBUTION 135

occurrence in other parts of the tropics is perhaps not
yet explained satisfactorily. Also we may record as
characteristic of this Ethiopian region a few peculiar
genera such as Nannodrilus and Gordiodrilus. Alma
being a partly aquatic genus is perhaps less distinctive
and as a matter of fact it strays into the Palaearctic
region, being found in the lower waters of the Nile.
It will be observed that with this exception the limits
of the Ethiopian region according to earthworms
agrees with that delimitation afforded by a con-
sideration of other groups since it stops short at the
Sahara, leaving northern Africa to be referred to the
Palaearctic region. At the same time we have an
analogy with South America as concerns the southern
extremity of the African continent; here we meet
with Notiodrilus and allied Acanthodrilinae just as in
Patagonia and—as also in that quarter of the world—
these forms just stray into the Ethiopian region
above—specimens of Notiodrilus being met with in
Madagascar as well as in tropical Africa. This bit
of Africa as it appears to me must also be cut off
from the Ethiopian region and included in an Ant-
arctic region. Madagascar offers a further problem.
Are we to include this in Ethiopia or speak of a
Malagasy region? Apart from a few forms which
are at least possibly to be looked upon as accidental
immigrants, such as members of the genera Pheretima
and Gordiodrilus, the fauna of Madagascar consists

136 EARTHWORMS AND THEIR ALLIES [cu.

mainly of many species of Kynotus. This genus, a
member of the sub-family Microchaetinae, of the
family Geoscolecidae, affines Madagascar to Ethiopia
and leads me to place both in the same region though
we may doubtless speak of a Malagasy sub-region.
We have now to consider the eastern region of the
world comprising the two regions known generally
to zoogeographers as the Oriental and Australian.
Taking a large view of the range of sub-families and
genera, and endeavouring to make the great regions
of the globe more or less equal, it seems difficult to
divide further a region which shall include all of this
vast territory, and which may therefore be termed
Indo-Australian. For we find as characteristic of the
entire stretch of country the great majority of the
genera of the huge family Megascolecidae. Indeed
the largest sub-family of this family, 7.e. the Megas-
colecinae, is, save for the mysterious occurrence of
the genera Plutellus and Megascolides in America,
absolutely limited to this area. Another sub-family,
that of the Octochaetinae, is limited to it. So far as
concerns the others of the sub-families of Megas-
colecidae it is only the Trigastrinae which occur here
(the genus Hudichogaster and a few possibly intro-
duced species of Dichogaster) and a scattered species
or two of Notiodrilus of the sub-family Acantho-
drilinae. Again there are a few and probably intro-
duced species of the sub-family Ocnerodrilinae. More

Ix | GEOGRAPHICAL DISTRIBUTION 137

important still this region has confined to itself the
family Moniligastridae ; for a species described some
years ago by myself from the Bahamas is doubtless
an introduced form. We have a complete absence of
indigenous Lumbricidae and Geoscolecidae excepting
the aquatic Glyphidrilus of the sub-family Micro-
chaetinae. It is true that by taking isolated tracts,
even large tracts, of this great regional expanse a
sub-division into well characterised regions can be
apparently recognised. But in taking such a step we
shall be confronted with the curious fact that it is
rather neighbouring than widely remote sub-divisions
which present the greater differences.

If we compare for example India and New Zealand
we find in common such striking genera as Octochaetus,
Hoplochaetella and Diporochaeta; whereas these
genera are absent from the intervening islands of
the great Malay archipelago. On the other. hand
Australia differs from the comparatively neighbouring
islands of Borneo and others by the absence in those
islands of the characteristic Australian genera such
as Megascolex, Notoscolex, Plutellus etc. which are
in their turn found in India. It is facts like these
which render very difficult the apportioning of the
tracts of country forming the eastern hemisphere
into separate regions.

There is no doubt that the Malay archipelago and
the adjacent coasts of Asia up to Japan differ from

138 EARTHWORMS AND THEIR ALLIES [cu.

both India and Australia by the almost entire limita-
tion of the genus Pheretima to them ; but we cannot
intercalate a region in the middle of another geo-
graphical area in this fashion !

The limitations of this great Indo-Australian
region now demand consideration. The chief difficulty
is offered by the islands of New Zealand and by some
of the smaller islands lying far from but still in the
neighbourhood of New Zealand. Are we to include
New Zealand in this region? There is no doubt that
the northern island of New Zealand is much nearer
to Australia in its earthworm fauna than is the
southern island. There are, it is true, a number of
genera peculiar to New Zealand, which are Rhodo-
drilus, Leptodrilus, Maoridrilus, Neodrilus, Plagio-
chaeta, Pereiodrilus, Dinodrilus, Dinodriloides, but
these do not represent the whole of any family or even
sub-family and they have all of them near relations in
other parts of the region as has been pointed out
—even to the peninsula of India itself. Again New
Zealand contains members of the genus Notiodrilus,
that characteristic Antarctic form. In fact New
Zealand would appear to be a transitional zone
between an Indo-Australian and an Antarctic region.

The last region into which the world can be
divided according to its fauna of earthworms is an
Antarctic. Iam of distinct opinion that this region
is quite necessary in spite of the views of some others.

Ix] GEOGRAPHICAL DISTRIBUTION 139

Although the genus Notiodrilus certainly, and
Microscolex possibly, extend into the tropical regions
of America, Africa, and Australia, these species are
but few, and the bulk of the species and of the allied
genus Chilota are restricted to the antarctic quarter
of the globe; they also extend all over it, that is to
say in the southernmost parts of South America,
in the Cape region of Africa, in Kerguelen and the
Crozet Islands, and in New Zealand, as well as in the
Auckland Islands and other neighbouring islands.
It is true that I have excluded New Zealand from this
region on the grounds that it forms a debateable
ground between it and the Indo-Australian. But
apart from this part of the world the rest of the
territories mentioned should be combined to form
the antarctic region.

Having therefore arrived at a mapping out of the
world into regions in accord with its earthworm
fauna, it is desirable to ascertain what light the facts
throw upon the geological and evolutionary questions
with which the study of zoogeography deals. The
existence of an antarctic region binding together such
distant points as South Georgia, the Cape of Good
Hope and Kerguelen Island, seems to argue strongly
for the former extensions northwards of the antarctic
continent so far north as to embrace these several
regions of that hemisphere. In view of the facts
relating to the danger of sea water to earthworms, to

140 EARTHWORMS AND THEIR ALLIES [cn.

their lack of facilities for migration, other than unas-
sisted locomotion, points which have been dealt with
earlier, it is difficult to explain their range in the
antarctic hemisphere on other grounds. The very
fact that the actual earthworm fauna of New Zealand
has led us on the whole to assign it to the Indo-
Australian regions shows the inherent uselessness of
the current view of zoogeography. For were we to
leave the matter here the relationship of New Zealand
to the regions of the world which lie to the south of
it would not be apparent. However, here as in so
many cases there is an antagonism between cut and
dried systems and the indications of evolution.

This assumed existence of a former antarctic
continent which connected Southern Africa and
Southern America as well as various islands has
perhaps a further justification in the distribution of
the Geoscolecidae. This family is divisible into two
well-marked sub-families of which one as has already
been mentioned is limited to South America and
another practically to Africa (the exceptions being
species of the largely aquatic Glyphidrilus), while
a third sub-family the Criodrilinae is more widely
distributed—again in accordance, one may perhaps
assume, with its largely aquatic mode of life. It is
also conceivable that the genus Dichogaster is
another example pointing the same way. The argu-
ments for regarding this genus as an indigene of the

Ix] GEOGRAPHICAL DISTRIBUTION 141

East are not strong. But there is on the other
hand no doubt that the Indian Hudichogaster is very
closely allied to it. But it is by no means excluded
from this argument to suppose that these Trigastrinae
owe their likeness to convergence. At any rate there
are examples of equally marked convergence which
seem to be as nearly proved as can be in another
though allied group. The New Zealand Neodrilus is
to all intents and purposes a Maoridrilus in which
one of the two pairs of spermiducal glands and
spermathecae has disappeared. It retains the charac-
teristic alternation in the position of the nephridia of
Maoridrilus, and other structural similarities unite
the two genera. In the same way species of Miero-
scolex seem as easily derivable from Notiodrilus.
Microscolex and Neodrilus are so near that had we
no such hint of their origin it would be reasonable to
place them in the same genus. They at least show a
marked convergence.

It will be noticed therefore that the facts of
their distribution agree, as it would appear, with the
structure of the terrestrial Oligochaeta. The primi-
tive characters of the genus Notiodrilus are to be
seen in the double spermaries and glands appended
to the duct, and the corresponding spermatheca,
in the absence, or very slight development, of the
papillae, so frequent in more specialised genera such
as Pheretima, and in the general simplicity of many

142 EARTHWORMS AND THEIR ALLIES [cu.

organs of the body which are more complicated else-
where. As one would expect with an archaic form
this genus is widely ranging, being found in all the
principal land masses of the globe except in the
Euro-Asiatic continent.

Furthermore geographical facts would at least be
not contradictory to the view that this genus, and
therefore the terrestrial Oligochaeta generally, origin-
ated in the Antarctic hemisphere and that in pushing
northwards it has given off various descendants which
survive in the various regions of the world. Basing our
views of the possibilities of range among earthworms
on the actual facts already dealt with, it would seem
that the peopling of America from Africa or of Africa
from America, if it has occurred, has not taken place
through Europe and the north generally. For other-
wise we should expect traces of the passage. It is
true that we actually have Hormogaster as a possible
sign that the Geoscolecidae have passed this way.
But that is an isolated case and may be referred to
the extension northwards of this particular genus
rather than as an indication of a whole migration
through those territories. Another conclusion which
a collocation of the various facts brought together in
this book appears to lead to is that the group of the
terrestrial Oligochaeta is relatively speaking a modern
one.

Convinced as we must be of the fact that range

Ix | GEOGRAPHICAL DISTRIBUTION 143

is only possible by unaided locomotion through con-
tinuous land areas, the fact that but few gaps occur
in the range of a particular sub-family or lesser group
seems to indicate that no great time has elapsed since
the specialisation of these different forms. The
dependence of earthworms upon vegetable mould also
points in the same direction and furnishes an argu-
ment for the belief that these animals only greatly
increased on the advent of abundant dicotyledonous
plants, and perhaps indeed were actually contem-
poraneous with them.

LIST OF LITERATURE REFERRING
TO EARTHWORMS

In the list given below I am only able to mention a few of the
larger works relating to this group. To give anything like a
complete list would demand many pages of titles. From the
works selected the reader can, if it be desired, find his way to
the remaining literature of the group.

A. GENERAL WORKS

Vejdovsky. System und Morphologie der Oligochaeten. Prag,
1884.

Beddard. A Monograph of the Oligochaeta. Oxford, 1895.

Michaelsen. Oligochaeten in ‘Das Thierreich. Berlin, 1900.

Michaelsen. Die Geographische Verbreitung der Oligochaeten,
1903.

Vaillant. Annelés in Suites & Buffon. Paris, 1886.

B. EartawormMs oF (1) AUSTRALIA

Fletcher. <A series of papers in Journ. Linn. Soc. New South
Wales, 1886-90.

Spencer. A series of papers in Proc. Roy. Soc. Victoria, 1892-5.

Michaelsen. In Die Fauna Siidwest-Australiens. Jena, 1907.

(2) New ZEALAND AND ANTARCTIC ISLANDS

Benham. Report on Oligochaeta of the Subarctie Islands of New
Zealand. Wellington, N. Z., 1909.

Benham. A series of papers in Quart. Journ. Micr. Sci. 1904,
Proc. Zool. Soc. 1904, 1905 and Trans. N. Z. Inst., 1901-10.

Beddard. In Trans. Roy. Soc. Edinb. 1891 and Proc. Zool. Soe.
1889.

LIST OF LITERATURE 145

(3) Asta
Michaelsen. The Oligochaeta of India etc. in Memoirs Indian
Mus., 1909.
(4) Europe

Rosa. Reyvisione dei Lumbricidi. Mem. Acc. Torino, 1893.

(5) AFRICA

Michaelsen. A series of papers in Mitth. Naturhist. Museum.
Hamburg, 1891-1911.
Beddard. Quart. Journ. Micr. Sci., 1890-95.

(6) AMERICA

Eisen. Mem. Calif. Acad., 1894-96.

Cognetti de Martiis. Mem. Acc. Torino, 1905-6.

Rosa. Ibid., 1895.

Beddard. In Hamburg. Magalh. Reise, 1895 and Nachtrag to
same by Michaelsen.

Also numerous other works by the above-named authors and
by Perrier, Horst, Ude, Lankester, Stole, Pierantoni, Friend,
Stephenson, Southern, Goodrich, ete., ete.

INDEX

Acanthodrilinae, 14, 78, 80, 82,
84, 87, 102

Acanthodrilus, 129

Aeolosoma, 34-36

Aeolosomatidae, 33, 34

African earthworms, 74

Agriodrilus, 31

Allolobophora, 62, 85, 111, 117-
119, 128

Alluroides, 40, 41

Alluroididae, 40

Allurus, 45

Alma, 24, 49, 50, 60, 61, 95,
135

Alpine earthworms, 123

Alvania, 75, 115

American earthworms, 71

Amphichaeta, 37

Anachaeta, 42

Anatomy of earthworms, 1

Andiodrilus, 72, 74

Andiorrhinus, 72

Anteoides, 72

Anteus, 72

Antarctic earthworms, 86, 138

Aptodrilus, 72

Aquatic earthworms, 44

Aquatic families of worms, 30

Arctic earthworms, 88
Argilophilus, 98, 133
Asiatic earthworms, 80
Astacopsidrilus, 37, 38
Athecospermia, 39
Aulophorus, 36
Aurantina, 39

Australian earthworms, 83

Barriers to migration, 124
Beddardiella, 76, 95, 115
Benhamia, 72, 92
Bettonia, 76, 115
Bimastos, 117
Bogertia, 75, 114,
Books and Memoirs upon earth-
worms, 144
Bothrioneuron, 38, 39
Branchiura, 38, 39, 70
Branchiodrilus, 36
Buttneriodrilus, 75, 115

Callidrilus, 48, 77

Cape of Good Hope, worms of,
76

Chaetogaster, 37

Chilota, 14, 72, 76, 77, 93, 126,
139

INDEX

Claparedilla, 39

Climate and distribution, 120

Clitellio, 38, 39, 53

Cocoons of worms, 62, 127

Criodrilinae, 24, 62, 85, 140

Criodrilus, 24, 48, 49, 62, 72, 85,
92, 98

Dendrobaena, 85

Dero, 36, 37

Desmogaster, 81, 94

Diachaeta, 73

Diaphorodrilus, 76

Dichogaster, 15, 22, 28, 56, 72,
74, 76, 80, 82, 83, 84, 92, 99,
104, 116-120, 129, 134, 140

Didymogaster, 84

Digaster, 84

Dinodriloides, 87, 138

Dinodrilus, 16, 55, 87, 138

Diplocardia, 85, 133

Diplotrema, 83

Diporochaeta, 19, 80, 84, 87, 94,
MST

Dispersal of earthworms, 113

Drawida, 57, 81

Eelipidrilus, 39

Hisenia, 85, 108

Hiseniella, 41, 45, 46, 49, 66,
85

Eminoscolex, 75, 115

Enantiodrilus, 72

Enchytraeidae, 31, 41

Environment, 59

Eudichogaster, 80, 136, 141

Eudrilidae, 25, 26, 28, 29, 61, 66,
75, 78, 86, 116, 134

Eudrilus, 66, 75, 78, 79, 82, 83, 86,
97, 98, 101, 104, 105

Eudriloides, 27, 75, 114

147

Eupolygaster, 57, 81, 94
Eupolytoreutus, 76
Euscolex, 76, 95, 115
Eutyphoeus, i6, 17, 80

Families of worms, 14
Fimoscolex, 72
Fletcherodrilus, 26, 84
Fresh-water worms, 30, 44

Gardullaria, 76, 115

Genera, range of, 90

Geographical distribution, 129

Geoscolecidae, 20, 22, 23, 46, 59,
61, 71, 76, 79, 86, 104, 132, 134,
136, 137

Geoscolecinae, 22, 23, 71

Geoscolex (= Glossoscolex)

Glossoscolex, 23, 72-74

Glyphidrilus, 48, 49, 77, 79,83, 98,
137, 140

Gordiodrilus, 76, 78, 81, 92, 99,
106, 135

Haplodrilus, 73

Haplotaxidae, 42

Haplotaxis, 31, 42

Heliodrilus, 75, 115

Helodrilus, 79, 85, 90, 91, 103,
1085 102; 7

Henlea, 41

Hesperodrilus, 38

Hesperoscolex, 23, 58, 72, 73

Holoscolex, 72, 76

Hoplochaetella, 80, 87, 93, 137

Hormogaster, 24, 85, 131, 142

Hormogastrinae, 24, 85

Howascolex, 78

Hyperiodrilus, 30, 75, 115, 117,
129

Hypogacon, 111

148

Tlyodrilus, 38

Ilyogenia, 22, 73
Tridodrilus, 76, 115
India, earthworms of, 79

Japan, earthworms of, 131

Kerguelen, earthworms of, 139

Kaffania, 75, 115

Kerria, 18, 73, 99

Kynotus, 23, 24, 29, 78, 95, 97, 131,
136

Lampito, 78, 80

Lamprodrilus, 39, 40

Leptodrilus, 86, 111, 112, 138

Libyodrilus, 28, 75, 115

Light, influence of, 67

Limicolae, 30, 47, 58

Limnodriloides, 31, 38

Limnodrilus, 38, 44

Liodrilus, 73

Lophochaeta, 38

Lumbricidae, 38,57, 61, 62, 83-86,
90, 103, 104, 107

Lumbriculidae, 37, 41, 48

Lumbriculus, 39

Lumbricus, 85, 90, 108, 120, 122

Lycodrilus, 38

Macrochaetina, 37

Madagascar, earthworms of, 77

Maheina, 14, 78

Malay region, earthworms of, 82,
137

Malodrilus, 76, 115

Man, hisinfluence in distribution,
106, 123

Maoridrilus, 11, 14, 87, 95, 138,141

Marine worms, 50

Megachaetina, 75, 114

INDEX

Megadrili, 44, 50

Megascolecidae, 14, 22, 29, 61, 75,
76, 79, 82, 87, 92, 99, 103, 136

Megascolecinae, 19, 22, 80, 82, 84,
87, 136

Megascolex, 19, 55, 62, 64, 80, 84,
93, 99) 137

Megascolides, 80, 84, 87, 93, 133,
134, 136

Mesoporodrilus, 39

Metadrilus, 75, 114

Metascolex, 76, 115

Metschaina, 75, 114

Microchaetinae, 24, 48, 76, 134,
136, 137

Microchaetus, 23, 77, 95

Microdrili, 31

Microdrilus, 92

Microscolex, 14, 72, 74, 83, 84,
94, 99, 102, 103, 106, 107, 139,
141

Migration of earthworms, 113

Millsonia, 92

Moniligaster, 57, 81, 99

Moniligastridae, 29, 41, 57, 61,
81, 83, 86, 94, 98, 137

Naididae, 33-35

Naidium, 37

Nais, 37

Nannodrilus, 18, 76, 135

Nemertodrilus, 75, 115

Nematogenia, 76, 81, 104

Neodrilus, 87, 95, 138, 141

Neumanniella, 76, 115

New Zealand, earthworms of, 86

Nile, worm of, 50

Notiodrilus, 14-16, 20, 22, 37, 47,
52, 72, 74, 76, 77, 83, 84, 86,
91-94, 111, 122, 126, 134-139,
141

INDEX

Notoscolex, 80, 84, 93, 137
Notykus, 75, 114

Ocnerodrilinae, 16, 32, 73, 76,
81, 136

Ocnerodrilus, 18, 22, 73, 76, 78,
81, 84, 92, 99, 133

Octochaetinae, 16, 80, 84

Octochaetus, 16, 62, 80, 87, 93,
94, 137

Octolasium, 85, 117

Oceanic islands, earthworms of
109

Onychochaeta, 23, 72, 73

Opisthodrilus, 72

’

Papillae, 64

Paranais, 36, 125

Parascolex, 75, 115

Pareudrilus, 75, 115

Patagonia, worms of, 139

Pelodrilus, 42, 111, 112

Peloryctes, 39

Peregrine species, 96

Pereiodrilus, 87, 138

Perichaetidae, 104

Perionyx, 19, 22, 82, 84, 95, 99

Perionychella, 84

Periscolex, 23, 56, 72, 73

Perissogaster, 84

Pheretima, 19, 23, 55, 60-64, 73,
78, 80, 82, 84,90, 94, 99, 102,
104, 105, 110, 111, 122-124,
131, 135, 138, 141

Phreatothrix, 39

Phreodrilidae, 37

Phreodrilus, 37, 38, 70, 111

Phreodriloides, 38

Phreoryctes (= Haplotaxis)

Plagiochaeta, 15, 55, 87,
138

111,

149

Platydrilus, 75, 114

Pleurophleps, 35

Plionogaster, 19, 29, 82

Plutellus, 80, 84, 87, 93, 95, 111,
133, 134; 136; 137

Polytoreutus, 25, 26, 58, 76

Pontodrilus, 50, 51, 125

Pontoscolex, 20, 22, 23, 66, 72-
74, 78, 79, 82; 83; 96, 97%; 98)
101, 102, 104, 105, 111

Preussiella, 75, 115

Pristina, 37

Psammoryctes, 38

Pygmaeodrilus, 76

Reithrodrilus, 75, 114
Rhinodrilus, 72, 73
Rhizodrilus, 39
Rhododrilus, 86, 111, 138
Rhynchelmis, 39
Ripistes, 86

Rosadrilus, 75, 115

Sea-shore, worms of, 50

Sea as a barrier, 124

Schmardaella, 36

Senses of worms, 65

Sparganophilus, 24, 47, 85, 92,
132

Spenceriella, 80, 84, 87
Structure (see Anatomy)
Stuhlmannia, 75, 114, 117
Stylaria, 37

Stylodrilus, 39

Sutroa, 39

Systematic arrangement, 14

Teleudrilus, 76, 115
Teleutoscolex, 39, 40
Teleutoreutus, 76, 115
Telmatodrilus, 38

150 INDEX

Temperature and distribution,
120

Thamnodrilus (see Rhinodrilus)

Titanus, 23

Tokea, 87, 134

Trichochaeta, 23, 53

Trichodrilus, 39

Trigaster, 80, 84, 85

Trigastrinae, 15, 72, 80, 82, 84,
136

Tritogenia, 77

Tubifex, 38, 44

Tubificidae, 33, 37, 38, 48

Tykonus, 72

Urobenus, 72
Urochaeta, 20

Vejdovskyella, 37
Vermiculus, 39

Woodwardia, 80, 82, 84, 93
Yagansia, 14, 72, 74, 76, 93

Zapotecia, 85

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i

ets

pabbisie