Earthworms and their Allies

THW

d to further observations upon the geographical distribution

ows 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 ana

regions may also be further subdivided. The commonly accepted regions were originally devised by Mr Sclater and are known as the Palaearctic, Nearctic, Neotropic, Ethiopian, 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

ion 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

erised by their earthworm inhabitants and see how far these regions agree

ich is really limited to it, and by just a few traces of other genera such as Hormogaster 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

umbricidae 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

hich Dr Eisen 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 abo

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 consideration as forming one great Neogaean region with three sub-regions, the North American, Central American and West Indian, and tropical South American. This region h

ts of the Ethiopian region according to earthworms agrees with that delimitation afforded by a consideration 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 appea

Megascolecinae, 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 Megascolecidae it is only the Trigastrinae which occur here (the genus Eudichogaster and a few possibly introduced species of Dichogaster) and a scattered species or two of Notiodrilus of the sub-family Acanthodrilinae. Again there are a few and probably introduced species of the sub-family Ocnerodrilinae. More important still this region has confined to

alay 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,

r from both India and Australia by the almost entire limitation of the genus Pheretima to them

and 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 Rhododrilus, Leptodrilus, Maoridrilus, Neodrilus, Plagiochaeta, Pereiodrilus, Dinodrilus, Dinodriloides, but these do not represent the whole of any family or even sub-family an

ustralia, 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 w

ensions 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 their lack of facilities for migration, other than unassisted 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 earthwo

its largely aquatic mode of life. It is also conceivable that the genus Dichogaster is another example pointing the same way. The arguments for regarding this genus as an indigene of the East are not strong. But there is on the other hand no doubt that the Indian Eudichogaster 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 grou

maries 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

s 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 otherwise 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. Bu

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 direct

ITERATURE

ARTH

oup. To give anything like a complete list would demand many pages of titles. From the works se

neral

Morphologie der Olig

ph of the Oligocha

aeten in 'Das Thier

aphische Verbreitung

s in Suites à Bu

rms of (1)

ers in Journ. Linn. Soc.

papers in Proc. Roy.

Fauna Südwest-Austr

and and Anta

f the Subarctic Islands of New

rn. Micr. Sci. 1904, Proc. Zool. Soc. 19

. Soc. Edinb. 1891 and

)

aeta of India etc. in M

Eu

i Lumbricidi. Mem.

Af

pers in Mitth. Naturhist.

. Journ. Micr.

Am

Calif. Aca

tiis. Mem. Acc.

Ibid.,

lh. Reise, 1895 and Nacht

and by Perrier, Horst, Ude, Lankester, Stole, Pierant

N

e, 14, 78, 80,

odrilu

soma,

matidae

earthw

drilu

, 62, 85, 111

ides,

oidid

uru

9, 50, 60,

earthwo

ia, 7

n earth

chaet

haet

of earth

rilus,

rrhin

oide

eus

earthwor

dril

earthw

amilies o

earthwo

hilus,

earthw

sidrilu

osper

phor

ntin

an earth

to migr

ella, 76

mia,

nia,

stos

tia,

moirs upon e

neuron,

ura, 38

iodril

odrilus,

rilus,

od Hope, w

ogast

72, 76, 77,

redil

nd distri

io, 38,

of worms

nae, 24,

, 48, 49, 62,

obaen

, 36

aster,

haet

rodril

2, 74, 76, 80, 82, 83, 84, 92,

ogast

ster

loides,

s, 16, 55

ardia,

otre

19, 80, 84, 87

of earth

da, 5

idril

ia, 8

41, 45, 46

colex,

iodri

aeidae,

onmen

ster, 80,

, 28, 29, 61, 66,

8, 79, 82, 83, 86,

des, 27,

ster, 57

toreut

x, 76,

eus, 16

s of wo

scol

rodrilu

ter worm

laria,

, rang

al distrib

46, 59, 61, 71, 76, 79, 8

cinae, 2

x (= Glo

colex,

8, 49, 77, 79,

76, 78, 81, 92

drilu

taxid

axis,

rilus,

85, 90, 91, 10

lea

rodri

olex, 23,

olex,

ella, 80,

er, 24, 8

strinae

scol

s, 30, 75, 1

gaeo

dril

enia,

rilus,

arthworm

arthworm

, earthwo

nia,

, 18,

24, 29, 78, 9

to, 7

drilus

s, 86, 111

lus, 28,

influen

ae, 30,

iloides

rilus,

rilu

chaet

57, 61, 62, 83-86

lidae, 3

iculu

85, 90, 1

dril

chaet

r, earthw

na, 1

, earthworms

ilus,

ence in distri

11, 14, 87,

e wor

etina,

rili,

, 29, 61, 75, 76, 79,

, 19, 22, 80,

55, 62, 64, 80

80, 84, 87, 93

rodril

ilus,

olex,

aina,

e, 24, 48, 76

etus, 23

odri

drilu

, 83, 84, 94, 99, 102,

of earth

soni

ster, 57

9, 41, 57, 61, 81,

dae,

diu

is

lus, 18,

drilus,

nia, 76,

, 87, 95,

iella,

d, earthwo

worm

, 52, 72, 74, 76, 77, 83, 84, 86,

x, 80, 84

us, 7

e, 16, 32, 73

22, 73, 76, 78,

tinae, 1

16, 62, 80, 8

sium,

ands, earth

aeta, 23

hodri

llae

ais,

olex,

rilus,

a, worms

us, 42,

ryct

ne spec

rilus,

aetida

19, 22, 82

nyche

ex, 23,

sogas

80, 82, 84, 90, 94, 99, 102, 104, 105,

tothr

drili

us, 37, 3

riloid

tes (= H

a, 15, 55,

rilus,

ophle

ster, 19

87, 93, 95, 111,

tus, 25,

lus, 50,

72-74, 78, 79, 82, 83, 96, 97

iella,

tina

oryct

odril

drilus,

rilus,

drilu

lus, 86,

helmi

stes

ilus,

re, wor

a barri

rdael

of wo

lus, 24, 47

ella, 80

re (see

nia, 75,

aria

drilu

roa

ic arran

rilus,

scolex,

reutus,

todri

and distri

us (see Rh

anu

a, 8

chaeta

odril

er, 80,

, 15, 72, 80

ogen

ex, 3

ae, 33, 3

onu

enus

haet

vskye

icul

ia, 80,

14, 72,

teci

Y JOHN CLAY, M.A. AT