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PUBLICATIONS OF THE UNIVERSITY OF MANCHESTER

BIOLOGICAL SERIES

No. IV

AN INTRODUCTION

THE STUDY OF RECENT CORALS

Published by the University of Manchester at

THE UNIVERSITY PRESS (H. M. McKechnie, M.A., Secretary),

23 Lime Grove, Oxford Road, MANCHESTER

LONGMANS, GREEN .^ CO.

London : 39 Paternoster Row, E.C. 4.

New York : 55 Fifth Avenue

Toronto : 210 Victoria Street

Bombay : 336 Hornby Road

Calcutta : 6 Old Court House Street

Madras : 167 Mount Road

AN INTRODUCTION

TO THE STUDY

OF RECENT CORALS

SYDNEY J. HICKSON

PROFESSOR OF ZOOLOUV IN THE UNIVERSITY OF MAN'CHESTER

MANCHESTER: AT THE UNIVERSITY PRESS

LONDON, NEW YORK, ETC.: LONGMANS, GREEN .^ CO.

1924

PUBLICATIONS OF THE UNIVERSITY OF MANCHESTER
No. CLXIII

MADE IN ENGLAND
All rights reserved

PREFACE

When a naturalist has the good fortune to spend a few
weeks or months within easy reach of a tropical coral reef
he gains an impression of animal and vegetable life which
he can never forget. It may be that his aesthetic sense is,
at first, stimulated and charmed by the beauty of shape and
colour that he sees, but his more permanent interest becomes
diverted to the intricate correlations of the multitude of
living organisms and the infinite variety of their form and
structure.

From the time of such an experience everything which is
brought to him from a coral reef by friends and seamen is
not only an object of interest, but often brings with it a
thrill of reminiscent pleasure. It is difiicult for him to
shake off, if he desired to do so, the fascination of the corals.

Since my visit to the coral reefs of North Celebes many
years ago I have received from several friends specimens
from the shores which they have explored, not only the hard
stony things called corals, but soft glutinous things, animal
and vegetable, fish, and some worms and sponges. I wish
I could find time and patience to describe the many points
of interest in all these things, but I must confine myself
within certain Hmits, and these must be the boundaries,
wide as they are, of my own conception of the meaning of the
word " coral." But if I write about corals I cannot hmit
myself to those of the coral reefs, for such things are not
restricted, as many may suppose, to the warm tropical seas
but are, as will be seen in the text, world-wide in their
distribution.

The immense numbers of genera and species of recent

VI CORALS

corals which have been brought to hght render the task
of compiling a complete systematic treatise on them a work
of such gigantic proportions that it is beyond the powers
of a single naturalist to complete it. All that has been
attempted, therefore, in this book is to place before the
reader a short description of a few illustrative genera of
each of the groups of animals and plants which form coralline
structures, to be a handy introduction to his studies and to
help him to distinguish the corals belonging to the different
groups.

It is dilhcult for students at home, who have only the
hard skeletal parts to handle, to realise that in their natural
haunts the corals are living, breathing, and feeding animals
or plants, and no study can be complete or satisfactory unless
some knowledge can be gained of the structures by which
they capture and digest their food, the colours thev displav
in life, and the means by which they propagate their kind.
A short account of the soft parts of the coral and of their
appearance when alive are therefore included, wherever
possible, in the description of the genera.

The accurate determination of corals is not only of
importance for the student of pure science, but it has its
economic value in the study of the problems of distribution
and variation of the coral reefs of the world. It may be
suggested that the sea-charts and marine surveys would be
more valuable than they are if some description were given
of the kind of coral of which dangerous reefs or shoals are
composed. If this little book will help mariners to identify
such corals it may serve a useful purpose.

I regret very much that I have not been able to include
in the text any reference to fossil corals. The story of the
evolution of corals is of extraordinary interest, and the part
played by them in building up many of the geological strata
is of the greatest importance. A book deahng with this
subject is greatly needed, but it should be a sequel to rather
than a part of such a book as is now presented to the public.

In compiHng the text I have had to consult many of
my colleagues in the different Faculties of the University. I
wish to acknowledge with gratitude their willing and valuable

PREFACE

Vll

assistance. The last chapter on the history of the trade in
coral could not have been written without the help of several
of my classical friends. I am also indebted to Sir Thomas
Arnold, Professor Pelliot, and Professor Parker for refer-
ences to coral in Arabic and Chinese literature.

Nearly all the illustrations are new, and have been
prepared by the Lyth Engraving Company from photographs
of specimens in the Manchester Museum or from drawings
by Miss D. Davison. Some of the photographs were taken
by Mr. J. T. Wadsworth of the Zoological Department, and
by Mr. J. W. Jackson and Mr. H. Britten of the Man-
chester Museum. To Professor W. C. Mcintosh, F.R.S.,
I am indebted for the fine specimen of Filogvana implexa
illustrated on p. 194.

S. J. HICKSON.

zZ til June 1924.

CONTENTS

PAGE

Preface . . . • • . . v

CHAPTER I

On the Use of some Words . . . . i

CHAPTER n

On the Structure and Classification of Corals . 15

CHAPTER in

Madreporarian Corals . • • • -23

CHAPTER IV

Madreporarian Corals {continued) . ■ .81

CHAPTER V
Alcyonarian Corals . . • • .103

CHAPTER VI
Antipatharian Corals . . • • -136

CHAPTER VII

Hydrozoan Corals . . • • • -MS

CORALS
CHAPTER VIII

I'OLvzoAN Corals

I'AGE

'57

CHAPTER IX

P'ORAMINIFERAN AND SOME OTHER CORALS . . .176

CHAPTER X
Coral Algae . . . . . -197

CHAPTER XI

Coral Reefs . . . . . .213

CHAPTER XII

The early Trade in Black and Red Coral . . 2^,1

Index

251

LIST OF ILLUSTRATIONS

FIG. FACE

1. A fully expanded Carj-ophyllia polyp . . .16

2. A group of four specimens of Caryophyllia smithii and one

specimen (black ring) of Balanophvllia regia .

3. Diagram of a transverse section through the cup of a

Caryophyllia ......

4. Diagram of an external view of a Caryophyllia

5. Lophohelia prolifera . . . .To face page 28

6. Diagram of a transverse section of a ]\Iadreporid calvx . 32

7. Diagram of the mesenteries of the Astraeid polvp Manicina

8. Diagram to show a stage in the division by fission of the

Astraeid polyp Manicina ....

9 and 10. Diagrams of sections of Porites polyps

11. Diagram to show a stage in the division of a polyp of

Porites .......

12. FlabeUuDi rtibniin .......

13. Lower part of figure a branch of Lophohelia, upper part

Lophohelia in blastogenic fusion with an Amphihelia

14. Oculina ........

44
46

15. Diagrams to illustrate the three princ

endotheca .

16. Galaxea caespitosa

17. Fa via

18. Goniastraea

19. DicJwcoenia pulcherrinia

20. Aleandrina

21. Euphyllia

22. Merulina

pal kinds of

49
51

To face page 53

54
. 56
. 58

Xll

Ki<;.
23-

24.

26.
27.
28.
29.
30-
31-
3^-
33-
34-
35-
36.
37-
38.
39-
40.
41.
42.
43-
44-
45-
46.

47-
48.
49.
50-
51-
5-2-
53-
54-
55-
5(^-
57-
58.
59-

CORALS

Fungia ......

'S'oung stalked form of Fungia
Herpetolitha .....

Sidcrastyaea radians ....

Siderastvaea siderea ....

Agaricia. .....

Pachyseris .....

Endopachys grayi ....

Diagram of septa of Endopachys
Heteropsammia ....

Astvoides calicularis ....

Seriatopora .....

Seriatopora with gall of crab Hapalocarcinus

Stylophora

Madrepora

Porites .

Turbinaria

Pyrophvllia inflata ....

Diagram of septa of PyropJiyUia inflata
Diagram of dimorphic Alcyonarian .
Spicules of Alcyonaria
Diagram of structure of Corallium .
Coyallium nobile ....

Diagram of transverse section of Alcyonarian

Spicules of Covallium nobile

Tubipova niusica

Heliopora coerulea

Hcliopora coerulea

I sis hippuris

Isidella neapolitana

Wrightella robusta

Gorgonia verrucosa

Primnoa reseda .

Prininoa reseda

I'AGE

To face page 65
68

To face page 70
71

To face p

73
age 74

75
77
77
79
80
82
84

To face p
To face p.

polyp
polyp

To face pa^

°/
92

age 95
98
age 98
100

lOI

104

105
108
108
log
109
no
112
119
ge 120
121
122

123
127

130
131

LIST OF ILLUSTRATIOI

Xlll

FIG.

PAGE

60.

Plexaura ....

• 132

61.

Ceratoporella nicholsonii

134

62.

Ceratoporella, surface view .

134

63.

Aiitipathes larix

.138

64.

Antipathes larix

• 139

65.

Antipathes {Tylopathes) flabellnm

To face page 140

66.

Millepora ....

146

67.

Diagram of a living ]\Iillepora

To face page i^j

68.

Millepora ....

To face page 148

69.

Nematocysts of Millepora

. 148

70.

Distichopora ....

151

71-

Distichopora ....

152

72.

Stylaster ....

154

73-

Erriua (Labiopora) aspera

155

74-

Diagram of structure of Polyzoan polyp

158

75-

Crisia eburnea ....

161

76.

Horneva lichenoides

162

77-

Retepora ....

165

78.

Adeona ....

166

79-

Lepralia foliacea

167

80.

Lepralia foliacea

168

81.

Cellepora ....

169

82.

Porella compressa

170

83.

Porella compressa

171

84.

Cellaria fistulosa

172

85.

Lagenipora . . . .

174

86.

Haswellia ....

175

87.

Polytret)ia niiniaceuDi .

179

88.

Surface views of Polvtrema, Homotrema, S

jporadotrema

180

8g.

Hoynotrema vubrum

181

go.

Sporadotretna cylindricum

183

91.

Sporadotrema cylindricum

183

92.

Sporadotrema niesentericum

184

93-

Gypsina .....

185

94.

Gypsina plana ....

185

95-

Ramulina herdmani

187

96.

Merlia normani

189

XIV

97-

98.

99.

100.

lOI.

102.
103.
104.
105.

106.
107.
108.
109.
no.

CORALS

Merlia nor))iani

Diagram of structure of Merlia

Filogrmia implexa

Filograna implexa

Lithothamniou

Lithothaninion diniorphum

Section of thallus of a Lithopliylluin

Section of tetrasporangial conceptacle of Lithothaninion

Section of young tetrasporangial conceptacle of a

Lithophyllum
A jHphiroa calif or nica
Galaxaura
Halimeda opuntia
Halimeda opioitia
Trade mark of First Coral Company

190
. 191

• 194

• 195

To face page 200
202
204
^05

^05
206
:209
210
210
242

CHAPTER I

ON THE USE OF SOME WORDS

A truly wise Man is so fully sensible how little he knows and
what Things he once was ignorant of, which he is now acquainted
with, that he is far enough from supposing his own Judgment a
Standard of the Reality of things." — Henry Baker, An Attempt
toivards a Natural History of the Polype, p. 216. 1743.

The origin of the word Coral is one of those things about
which we are still in doubt. The English form of the word
is of course derived from the Greek KopaXkLov or its
Italian equivalent Cor allium, and according to various
authors the Greek form was derived from ;^6t/9aA,(oi/ = what
becomes hard in the hand, or Kopr) and aXo9 = the maiden
or nymph of the sea, or Kpjp and aXo'? = the heart of the sea
(with reference to its colour).

But all these hypotheses as to the derivation of the
ancient Greek word seem to rest on very slender foundations.

It has been suggested by Reinach ^ that the word was
of Celtic origin, and this suggestion is quite consistent with
a more general view, which it is perhaps safest to adopt,
that it was incorporated into the Greek language from the
tongue of some wilder race of European nomads, who used
it for ornamenting their weapons in prehistoric times.

What is certain, however, is that it was used in the
early days exclusivel} as the name of the substance which
is now called Precious coral, the Corallium nobile of the
Mediterranean Sea, the axis of which has been used from
very ancient times as a jewel or charm.

^ S. Reinach, Reviie Celtique, xx., 1899.

I B

2 CORALS

The derivation of the word from -^eipaXiov was probably
suggested by the belief of the ancients that the Precious
coral is soft in the sea and hardens when exposed to the air.

Sic et Corallium, quo primum contigit auras
tempore, durescit ; mollis fuit herba sub undis.

Ovid, Metani. xv. 416-7.

This idea prevailed for a great many centuries, and it is not
clear who was the first to prove its error ; but Imperato
writing in 1699 denied its accuracy, and even before that
time Nicolay ^ had assured himself that the axis was hard
in the water by making the sailors plunge their hands into
the sea to test it before the coral was brought on deck.

In the sixteenth and seventeenth centuries we find the
word Coral applied to other things than the Precious coral,
thus Gesner (1565) called the coral now known as Oculina
CoraUiuni verrucosuni, and Lobel (1575) the coral now
known as Dendrophyllia Coralloides sive Corallii varietas.
Imperato applied the name Corallium album to examples
of several w'hite corals, but also introduced the name Poms
maironalis ramosits, from which the generic name Madrepore
has been derived for Dendrophyllia, and the word Millepora
for the coral now known as Caryophyllia.

From that time onwards the word Corallium and the
modernised forms of it. Coral, Corail, Koralle, Corallo, etc.,
have been applied to such a variety of animal and vegetable
marine organisms that it has lost its original restricted
meaning. It is difficult, therefore, to give a definition of
the term Coral that would satisfy at the same time modern
usage and historical research. But some kind of definition
must be attempted in order to indicate the scope of the
present work, and in making this attempt I shall endeavour
to convey the meaning that the word has acquired.

It is clear from what has already been said that the
Precious coral of commerce must be included in the defini-
tion, and it is also clear that the large white Madrepores

1 Nicolas tie Xicolay, who is described as the " valet de chambre et
geographe ordinaire " to the King of France, was sent in 1551 to the coast
of Algiers to investigate and report upon the coral fisheries of that region
(Masson).

ON THE USE OF SOME WORDS 3

and Brain corals of the Coral reefs cannot be left out.
All these things are undoubtedly members of the Animal
Kingdom and belong to the group of animals known as the
Coelenterata.

Moreover, if I were on a Coral reef with a few friends
of good education but not of scientific tastes, and were to
show them a Nullipore, they would in all probability call
it a Coral, and I should regard myself as a pedant if I said,
" No, it is a coralline alga," and the same if I denied that
the pieces of Lithothamnion brought up in his trawl by the
fisherman in the English Channel were corals, because they
happen to be plants. To restrict the use of the word Coral
to organisms or the products of organisms that are animals
would be to change the meaning the word has acquired in
everyday language, and a fortiori to restrict the use of the
term to animals that belong to that subdivision of the
Animal Kingdom called the Coelenterata would also be most
undesirable and impracticable.^

Nevertheless, the word as it is used by men of science
and by the general public has some definite restrictions.
It is not used for anything except certain animals and plants
or the productions of animals and plants that live in sea-
water or have lived in sea-water in prehistoric times. It
is used principally for such animals and plants that produce
a solid skeletal (or more accurately shell) structure of calcium
carbonate which persists as such entire, after the death
of the living organisms that produced it. The corals are,
moreover, sedentary organisms, that is to say they are
either fixed to some other hard substance at the bottom
of the sea, or, if free, are incapable of moving about from
place to place.

According to this definition, therefore, the things in-
cluded in the term Corals are the calcareous marine plants,
certain Foraminifera and Sponges, the Madreporarian corals,
certain Alcyonaria (such as the Precious coral) , and H3^drozoa,
and also some genera belonging to the Polyzoa and Annelida.

^ Coral — A hard calcareous substance consisting of the continuous
skeleton secreted by many tribes of coelenterate polyps for their support
and habitation (Murray's New English Dictionarv).

4 CORALS

It is a word, in fact, which has no longer any defined meaning
in zoological and botanical systematics, but signifies simply
a heterogeneous group of organisms or the products of
such organisms that have the common habit of living in
the sea and producing a shell structure of carbonate of lime.

Such a definition, or rather attempt at a definition, is
incomplete without reference to some special cases. There
is a certain group of animals, known to the zoologists as
the Antipatharia, which produce a hard black axial structure
of keratin or horn, and the substance of this structure can
be polished and used in the same way as the Precious coral.
It was used by the ancient Greeks as an antidote {dvnirad^'}^)
to poison, it was called by many writers of the sixteenth
and seventeenth centuries the Coralliitm nigrum, and is
still called Black coral in the shops where it is sold. Some
reference to the Antipatharia, therefore, should be made
in any general account of Corals, although they do not
secrete any calcium carbonate and are not included in the
general definition of the word.

The large subdivision of the Animal Kingdom called the
Mollusca, and also the Brachiopoda, include many forms
that are sedentary in habit and secrete shells of calcium
carbonate, but all of these must be excluded from the
definition, for I do not believe that the name Coral has ever
been applied to them by serious students of Natural History.

A more difficult question to decide is whether to include
in a general treatise on Corals, the Alcyonaria with hard
axes of horny substance or with axes composed of both
horny and calcareous substance which have been known
for a long time under the general name of " Gorgonia."
There can be no doubt whatever as to their close zoological
relationship with the Precious coral, and one genus of them,
namely Isis, was known to Imperato as Corallium articu-
latum and to later writers as the " King Coral " or " Jointed
Coral." On the other hand, they are also closely related to
the soft and spongy Alcyoniums (Dead Men's Fingers) of our
own coasts and the Sarcophytums of the coral reefs which
were not usually given the name Coral by the older writers.^

1 See, however, Milne-Edwards on p. 6.

ON THE USE OF SOME WORDS 5

There are a few Alcyonaria such as the Blue coral (Helio-
pora), the Organ-pipe coral (Tubipora), the Precious coral
(Corallium), and some others that are less known which
must still be classed with Corals on the ground that they
form compact shell structures of calcium carbonate that
do not disintegrate into isolated spicules on maceration in
sea-water ; but in my opinion many of the Alcyonaria
should not be called Corals.

The large and heterogeneous group of organisms which
were formerly known as Corallines, also presents us with
many difficulties. Some of these, such as the Polyzoan
genus Cellepora, formerly classed with the " Cell-corallines,"
cannot be omitted from a general treatise on Corals, but
the majority of the Polyzoa and also Hydrozoa with chitin-
ous or horny tests, such as the Pipe corallines (Tubularia)
and the Herring-bone or Vesicular corallines (Sertularia,
etc.), are not corals in the usual meaning of the word.

It will be seen from this attempt to define the word
" Coral " that it is a word of very ancient origin which,
from having a very restricted application to one kind of
marine product, has gradually acquired in the course of
the ages a vague and ill-defined meaning. It conveys now
to the mind not a definite species of the Animal Kingdom
but a strange assortment of marine organisms both animal
and vegetable, which make a hard calcareous, or in some
cases horny, structure that resists disintegration after the
death of the living tissues.

No attempt to restrict its use to its original meaning,
and to invent such terms as " false corals " or " coralloids "
or " pseudo-corals " to everything of this nature except
the species of the genus Corallium as it is now used, could
possibly be accepted. It would lead to such absurdities of
language that you might search the coral reefs of the world
and not find a single species of the true coral. It would
necessitate the alteration of many thousands of labels in
the museums and would create confusion in our literature.

The difiiculty of defining a word such as Coral, that has
come into popular use and has reference to things that are
not fully understood even by those who have made a pro-

6 CORALS

longed stud}^ of them is, as a matter of fact, insuperable.
And it is the same with many other zoological words and
expressions, because, as we become better acquainted with
the vast number of species and varieties of animals and
plants which exist in the world, the more clearly do we
realise that our systems of classification and the frontiers
we establish between one group and another are artificial
and unnatural. If we knew all that could be known about
animals living and extinct we should find that there are
no boundaries separating one group from another, but a
continuous series of forms showing tendencies to a great
increase in numbers in certain parts of its course or in certain
periods of time.

It is not surprising, therefore, that as our knowledge
expands our system of groups is changed, and with the
change there comes inevitably an alteration in the meaning
of words. Such a change of meaning in the word Coral has
taken place during the sixty-five years that have elapsed
since (in 1857) Milne-Edwards published the important
treatise entitled Histoire natnrelle des coralliaires on polypes
proprement dits. In this great work the class of the
Coralliaires was defined as " Radially symmetrical animals
with the following characters : (i) A centrally placed mouth
surrounded by tentacles and no true anus ; (2) the body
provided with a single system of cavities of which all parts
communicate freely with one another and with the exterior ;
and (3) the organs of generation are situated in the general
cavity of the body." With this definition of the Coralliaires
the distinguished French author included in the treatise not
only the Alcyonaria and Zoantharia that form coralline
structures of calcium carbonate, but also the whole group of
the Sea-anemones, the spongy Alcyonidae, the Order of the
Sea-pens (Pennatulacea), and several other forms that are
not, at the present day, usually called Corals. On the other
hand he excluded from his treatise all the coralline Algae,
Protozoa, and Polyzoa, and if he had been in possession of
the knowledge we have gained since his time he would also
have excluded, on the strength of his definition, such im-
portant corals as Millepora and the Stylasterina.

ON THE USE OF SOME WORDS 7

The word " polype " used in the sub-title of his work
needs a few words of comment at this stage, as it also has
changed its meaning to some extent.

The Greek word 7ro\v7rou<i (Latin polypus) or " many-
footed," was applied by Aristotle and other ancient writers
to the cuttlefish or octopus, and from this word was derived
the French word " poulpe," signifying a cuttlefish. When
the naturalists of the eighteenth century examined the living
corals and saw emerging from the outer crust a number of
small animals of tubular form, with a mouth at the free
extremity surrounded by a circlet of tentacles, they were
reminded of the cuttlefishes and octopuses with which they
were well acquainted.

Thus Peyssonnel, writing about the Precious coral, said
that he had discovered that " la fieur de cette pretendue
plante n'etait au vrai, qu'un insecte semblable a une petite
ortie {i.e. sea-anemone) ou poulpe." And Trembley, in the
account of his remarkable observations on Hydra, refers to
it as the " polype d'eau douce." The great French entomo-
logist Reaumur, however, who, assisted by Bernard de
Jussieu, repeated Trembley's experiments on Hydra, must be
held responsible for the establishment of the name polype
for these animals because " leurs cornes sont analogues aux
bras de I'animal de mer qui est en possession de ce nom "
{i.e. poulpe).

When later observations showed that the polyps of
the Hydrozoa differed in structure from the polyps of the
Anthozoa and these in their turn from the polyps of
the Polyzoa, an attempt was made to restrict the use of the
term to the polyps of the Anthozoa. Milne-Edwards, how-
ever, protested against this restriction as being prejudicial
to the interests of science, and said that the word could be
usefully maintained for the soft and contractile parts of the
Polyzoa, the Hydrozoa, the Alcyonaria, and the Zoantharia,
and should not be employed for one or more zoological
groups to the exclusion of others.

In modern times the word polyp has still a vague
and ill-defined meaning. It is applied to the isolated fresh-
water Hydra and to the animals that construct the horny

8 CORALS

and calcareous structures of the Hydrozoa, Zoantharia, and
Alcyonaria. In the group of the Polyzoa the derivative
word " polypide " is usually employed for those parts of
the body of the animals that are capable of extension and
retraction, and the word polyp is rarely used with reference
to the solitary sea-anemones.

In the case of several H}'drozoa and some of tlie
Alcyonaria the animals that build up the structure of a
single colony are found to be of two or three different
kinds, performing different functions in the economy of the
colony as a whole. In these cases great confusion has arisen
as to the use of the word polyp.

Thus Kolliker suggested that in the dimorphic Alcyonaria
the word polyp should be restricted to those individuals
of a colony that exhibit the full number of tentacles and
mesenteries, and the word " zooid " employed for those
individuals in which the tentacles and mesenteries are re-
duced in number or absent. This proposal is obviously
inconvenient, although it has been constantly maintained
by the German writers, because it suggests a homological
difference between the two kinds of animals of such a
colony which does not exist. It would be better to use
some prefix to the word polyp, such as auto- and siphono-,
to indicate the difference in structure. But this has not
been done. Another word has been introduced which lends
itself more readily and euphoniously to the use of prefixes,
and instead of auto-polyp and siphono-polyp, for example,
the words auto-zooid and siphono-zooid are employed. The
word " zooid " then may be regarded as a synonym of the
word " polyp," but, whereas the latter is used only in a
general sense, the former may be used with a prefix to
signifv a particular kind of polyp or zooid.

Thus, in speaking of the Precious coral, it may be said
that the colony is formed by a number of polyps, and that
these polyps are of two kinds, which are called the auto-
zooids and the siphonozooids respectively.

The word polyp has thus come to be used in very much
the same sense as Milne-Edwards used it in the sub-title of
his book, " polypes proprement dits," but the word coral

ON THE USE OF SOME WORDS 9

has become extended in its meaning to include living struc-
tures, such as certain Foraminifera, Sponges, and the coral-
line Algae for example, that possess no such organised animal
forms as could be, by any possibility, included in the mean-
ing of the word polyp. There can be no longer, therefore,
any synonymy between the words " Coral " and " Polyp."

Another word which must be frequently used in a book
on Corals is the word " Individual," and this is as difficult
or even more difficult to define than any of the others.
Many attempts have been made by eminent philosophers,
such as Huxley, Bergson, and others, to give a scientific
definition of it, but each one seems to lead to absurdities
or to a use of the word in a sense that it is not used and
cannot be used in common language. To give just two
examples to illustrate my meaning. If we were to accept
Huxley's definition of the word individual as " the total
product of a fertilised ovum," we must regard the winged
insect, the Aphis, which we find on our rose trees, not as an
individual but as the millionth (or more) part of an individual.
Or if we follow Bergson's analysis of the word, then we are
led to the conclusion that the Yucca plant and the Pronuba
moth, which are known to be mutually dependent on each
other for continued existence, are not two individuals but
one individual of the fifth or sixth order of individuality.

In my opinion the only definition of the word that can
bring it into agreement .with its usage in modern language
in biology is one which expresses the discontinuity of an
organism in time and space.

In the case of an isolated polyp such as a hydra or
a sea-anemone, there is no difficulty in grasping the idea
of the individual, and, if the hydra is reproducing by
gemmation, the bud that is not yet detached from the body
wall is a part of the individual hydra. When the bud has
developed tentacles, and has lost organic continuity with
the parent hydra, it becomes a separate individual. The
idea of separate individuality in this case is dependent on
the discontinuity in space.

In the genus Diaseris there is a single free individual
polyp which secretes a large fungiform calcareous structure.

10 CORALS

When it has reached a certain size or under certain unknown
environmental conditions, it breaks up into four segments,
and each of these four segments continues to hve inde-
pendently and in time restores the symmetrical shape of
its parent. In this case the single individual Diaseris has
given rise to four individual Corals of the genus.

An Alcyonium, a Tubipora, or a Madrepora is an organism
consisting of a number of polyps in organic continuity and
mutually dependent on one another for their continued
existence.

Here again the Alcyonium or the Tubipora as a whole
is, in common language, the individual, and the polyps part
or organs of the individual. The conception of individuality
has no relation to the structure or function of the parts but
to the discontinuity of the living organism as a whole from
other living organisms.

One difficulty, however, in the way of accepting this
definition of the word individual is that the corals which
are compound or formed of numbers of polyps in organic
continuity are frequently called " colonial " corals, and it
seems impossible to reconcile the conception of " colony "
with that of " individual."

But the word colony was introduced into the science in
error and is really a misnomer. It might be applied to the
bees in a hive or to the ants in an ant-nest, for these insects,
although congregated together for their mutual advantage,
are individually free, and it was due to the error of Reaumur
and others of his time, who regarded the calcareous structure
of corals as formed in the same way as bees or wasps con-
struct their combs, that the expression " coral insects "
came into use and the conception of colony formation was
introduced.

As the English-speaking people become accustomed to the
use of the word "polyp" the expression " coral insect " may
disappear from our language, but it will be more difficult to
eradicate the use of the word colony as applied to these
animals, because there is no other word in our language
which can be readily substituted for it.

" Zoophyte " is another word which was formerly applied

ON THE USE OF SOME WORDS ii

to many of the corals and other hving organisms which have
a plant-hke form or method of growth. According to Milne-
Edwards the first record of its use in this sense is to be
found in an edition of the writings of Elien by P. Gyllius,
1535- ill which these words occur, " Plinius urticam et
spongiam numerat inter ^co6(f)VTa." ^^'hatever may have
been the more restricted application of the meaning of the
term in the days of the classical writers, we find it applied
in the eighteenth century to all the Corals, Hydroids,
Gorgonians, Polyzoa, coral Algae, and even to some of the
Protozoa {e.g. Vorticella) and Rotifera {e.g. Brachionus).
The general idea underlying the use of the term was that
these things were neither wholly animal nor wholly vegetable
in nature but in some respects animal and in other respects
vegetable.

In this connexion a view expressed by Rumphius is of
some interest. He gives a description of a marine product
which he found at Amboyna (probably a Cavernularia)
called the " Phallus marinus," and, in describing its position
in the classes, says that in the element of the water there
are things which are hardly animals or plants but seem to
be the relics of primordial chaos, and among these there
are living, growing, and mineral things, such as plants
which are alive, stars which grow, and animals which resemble
plants.^

Pallas ^ was of opinion that Nature connects together
even the most different things and thus has brought together
the Animal and Vegetable Kingdoms in the form of the
Zoophyta, for these things combine the nature of animals
with the nature and form of plants.

In the middle of the eighteenth century, however, the
current views of the nature of the Zoophytes were shaken
by the publication of the remarkable observations and
experiments of Trembly on the freshwater Hydra and of
Ellis on certain Hydroids at " Brighthelmstone in Sussex "
and on Alcyonaria at Whitstable. To Peyssonnel, how-
ever, must be given the credit of having been the first to

1 See heading of Chapter III. p. 2^.
- Pallas, Elenchiis zoophytorum, Sections xv., xvi., xvii., xviii.

12 CORALS

demonstrate by observation and experiment that these
things are animals. Peyssonnel conducted his investiga-
tions on the Precious coral in the neighbourhood of Marseilles
in 1724 and 1725, and wrote an account of them in which
he clearly expressed his view as to the purely animal nature
of the Coral polyp.

But the views of the leading authorities of the French
Academy, and particularly of Reaumur, were so firmly
fixed that it was considered to be an act of charity to
Peyssonnel to refuse to publish his revolutionary opinions,
and even when he sent a communication on the subject
in 1753 to the Royal Society of London, which was pub-
lished three years later, the name of the author was
suppressed. Fortunately Peyssonnel's manuscripts were
preserved in the library of the Natural History Museum
in Paris and due credit has since been given to him for his
discoveries.

Ellis, 1 whose work was certainly done without knowledge
of what Peyssonnel had written, expresses his opinion
very clearly in the following sentence : "I own I am led
to suspect that by much the greatest part of those Sub-
stances, which from their Figure have hitherto been reputed
Sea Shrubs, Plants, Mosses, etc., are not only the Residence
of Animals, but their Fabric likewise ; and serve for the
Purposes of Subsistence, Defence and Propagation, as much
as the Combs and Cells fabricated by Bees, and other Insects,
serve for similar Purposes."

The result of these investigations was that Linnaeus
removed the Zoophytes from the Vegetable to the Animal
Kingdom, where they have remained ever since, but in doing
so he retained a modified form of the older view as to the
dual nature of these organisms.

It is not quite clear what Linnaeus really believed about
the Zoophytes, but judging from the brief statements he
gives in Latin he thought that the stem is vegetable but
becomes metamorphosed into animal when it flowers —

stirps vegetans, metamorphosi transiens in florens Animal.

^ J. Ellis, Natural History of the Corallines, p. loo. 1755.

ON THE USE OF SOME WORDS 13

" The Zoophytes are not, hke the Lithophytes, the
producers of their shells or trunks but the shells of them-
selves ; for the stems are true plants which, being meta-
morphosed, change into animated flowers (true animalculae)
completed by organs of generation and instruments of
motion, in order that they may obtain motion which ex-
trinsically they have not got."

The Lithophytes of Linnaeus consisted of the genera
Tubipora, Madrepora, Millepora, and Cellepora, and he
seems to have regarded them as entirely animal in nature.^

Linnaeus was the last of the great naturalists of the
eighteenth century to cling to the view that the Zoophytes
are wholly or in part of a vegetable nature.

But John Ellis, 2 one of the most brilliant and observant
naturalists of his time, who expressed most emphatically
the view that the Zoophytes are entirely animal in nature,
was led into the error of asserting that certain calcareous
Algae which he had studied are also produced by animal
organisms. Influenced perhaps by a statement made by
Linnaeus that all calcareous substances must truly be of
animal production, he included in the Animal Kingdom the
Corallines which are now called Lithothamnion, Amphiroa,
Corallina, Halimeda, etc. (see Chap. X. p. 197).

In justice to him, however, it is only fair to quote a
passage which shows that he held this view with some
misgiving.

" What and where the link is that unites the animal
and vegetable kingdoms of nature no one has yet been able
to trace out ; but some of these corallines appear to come
the nearest to it of anything that has occurred to me in all
my researches ; but then the calcareous covering, though
ever so thin, shows us that they cannot be vegetables."

It is not surprising that, as a result of the researches
of Peyssonnel, Ellis, and others, the word zoophyte gradually
fell into disuse. De Lamarck (18 16) said : " It is not at
all convenient to give to Polyps the name Zoophytes because

1 Animalia MoUusca, composita Corallium calcareum, fixum, quod
inaedificarunt animalia affixa {Systema Naturae, xii. ed. i. pt. 2, p. 1287).
- J. Ellis, Phil. Trans. Roy. Soc, 1767.

14 CORALS

they are solely and completeh' animals, for their body is
no more vegetative than that of an insect or any other
animal."

The fate of the word, however, was not sealed until,
by the researches of Tozzetti and subsequent authors, the
Nullipores were proved to be " uniquement et completement "
vegetative, and the position was then reached, which may
be safely regarded as final, that some Zooph3'tes are animals
and some are plants, but there are none which partake
of a dual nature, being animal in some respects and plants
in others.

But is it necessary that this word should entirely dis-
appear from our literature ? Perhaps not. If it is used
collectively to signify that strange assortment of animals
belonging to several distinct orders of the Animal Kingdom
which have a plant-like habit and method of growth, it
has a place in our vocabulary which is not otherwise pro-
vided for.

CHAPTER II

ON THE STRUCTURE AND CLASSIFICATION OF CORALS

" II n'y a dans le Corail ny fleurs, nv feuilles, ny chair, ny graine,
ny racine et cela pose, je crois qu'il est bien eloigne du genre des
plantes." — Boccone, 1674.

The large and very heterogeneous assembly of organisms
forming the calcareous or horny structures which are com-
monly called Corals may be divided into two great divisions :
the Animal corals and the Plant corals.

The Animal corals may be again divided into two
groups, namely, those that bear polyps and those that
do not bear polyps ; and the Plant corals also into two
groups, the Red Seaweed corals and the Green Seaweed
corals.

The polyp-bearing corals must be subdivided into a
number of orders according to the anatomical characters
presented by the polyps, but before this further sub-
division can be made clear to the reader it is necessary
to refer very briefly to essential characters presented by
these animals.

There can be no doubt that when the word poulpe or
polyp was first introduced in this connexion the important
differences between different kinds of polyps, which more
modern researches have revealed, were not understood nor
even suspected.

The word has no precise zoological meaning in modern
literature, but still retains its utility when applied to animals
which present certain superficial external characters in
common. It is not a word for which we can find a rigid
definition, and the student of zoology must be prepared to

CORALS

find many examples of organisms which may or may not be
called polyps according to the inclination of different authors.
But in general terms a polyp is an animal which is
sedentary in habit and more or less C3'lindrical in shape,
which possesses a mouth, surrounded by a crown of tentacles,
and an alimentary canal or a body cavity in which food is
digested.

There are many polyps which are solitary, but more
generally they build up, by budding or by division, colonies
of polyps in organic continuity with one another. If we

take an example of
a solitary polyp, the
coral Caryophyllia
(Fig. i), we can see,
when it is fully ex-
panded, that it pos-
sesses a mouth placed
in the centre of a
disc surrounded by a
single ring of ten-
tacles. In a colony
of polj'ps, as is shown
in the diagram of an
Alcj'onarian (Fig. 44) ,
we see a number of
polyps connected to-
gether in a common
fleshy substance (the
coenenchym) by a system of canals (coenosarcal canals).
Sometimes we find that the polyps in such a colony are all
alike in structure ; in other cases we find they are of two
kinds, as in the diagram, when the}' are called dimorphic
colonies. In the dimorphic colonies the two kinds of polyps
perform different physiological functions and show different
structural characters in adaptation to the performance of
those functions. In such cases the word zooid is used instead
of polyp, with a prefix to indicate in some way the functions
it performs {e.g. Autozooid and Siphonozooid in Fig. 44).
The reasons for calling the polyps Animals can now be

Fig. I. — A fully e,\paiided Caryophyllia polyp,
showing the slit-like mouth in the centre and the
ring of capitate tentacles surrounding the oral disc.
(After de Lacaze-Duthiers.) x li.

STRUCTURE AND CLASSIFICATION 17

explained. The tentacles are organs for catching and in
some cases killing or paralysing the food which passes within
their reach in the surrounding water, and the food is passed
through the mouth into a cavity where it is digested. The
food consists of various floating or drifting micro-organisms,
mostlv animal in nature, so that this method of feeding is
similar to that of other animals or, as it is called in technical
language, holozoic.^

The polyps also possess the power of mov^ement. It is
true that they cannot move from place to place in search
of their food as the higher animals do, but they are provided
with bands of muscles which enable them to expand and
retract their bodies. They are sensitive and irritable,
responding by muscular movements to stimuli of light,
heat, and chemical change in the surroundings.

They produce in a season of the year eggs and sperms,
and the eggs when fertilised give rise to ciliated larvae
which swim aw^ay and develop into a new polyp or colony
of polyps. All these characters, combined with features of
more minute structural anatomy which it is not necessary to
describe in detail, prove that the polyps are solely and com-
pletely animal in nature.

Some of the polyp-bearing corals possess an additional
character which Linnaeus considered to be also an attri-
bute of animal life only, but which we now know^ may
also occur in plants, that is, the secretion of calcium
carbonate.

The calcium carbonate is secreted in various ways in
different kinds of corals, but there is this in common to all
of them, that it is always secreted by cells of the outer layer
of the body — the ectoderm — and is therefore, strictly speak-
ing, an outside support or exoskeleton, although in some
corals it becomes deep-seated and internal by subsequent
changes in its relation to the soft parts.

The calcium carbonate which is secreted by the ectoderm
cells solidifies to form the complex calcareous structures of
such varied shape and structure with which we are famnliar
in our museum collections as the " Corals." The word

^ For a further note on the nutrition of corals, see p. 20.

i8 CORALS

Coral, however, being generally used in a very indefinite
way, may mean in our common language either the dried
calcareous skeletal structure alone or the whole living
organism with hard skeleton and fleshy organs complete.
It is therefore necessary to use the term " Corallum " when
we desire to refer to the calcareous structures only, in contrast
to the soft flesh}' tissues that give rise to them.

To return to our system of classification.

The polyp-bearing corals belong to two widely separated
divisions {i.e. Phyla) of the Animal Kingdom, called the
Coelenterata and the Polyzoa.

It is not necessary to relate in detail the many anatomical
and embryological differences between these two Phyla, for
which reference should be made to one of the many good
text-books of General Zoology. But there are two essential
points to which attention may be called.

In the Coelenterata the mouth leads into a large un-
divided cavity in which the food is digested, and the in-
digestible parts of the food are ejected by the same aperture.
In the Polyzoa the mouth leads into a stomach and intestine,
and the indigestible parts of the food are ejected by an anal
aperture which is quite distinct from it (Fig. 74, p. 158).
There is thus a complete alimentary canal in the Polyzoa
which is without any direct communication with the body
cavity surrounding it.

In all the Coelenterata without exception the tentacles
are provided with remarkable vesicles of microscopic size
called " Nematocysts," and these have the power of inflicting
a sting which kills or paralyses small animals that pass by
and captures them by means of a thread that is discharged
at the same time.^ The Coelenterata are therefore animals
that capture their prey by stinging them, and hence the
name Cnidaria (from KviS7] = Si nettle) is sometimes applied
to them.

In a few corals {e.g. Millepora) the nematocysts are
powerful enough to penetrate the human skin, causing a
painful form of nettle-rash, but as a general rule living
corals can be handled freely without any ill effects.
1 See Fig. 69 on p. 14S.

STRUCTURE AND CLASSIFICATION 19

The Polyzoa never possess nematocysts. Their food
is obtained by the action of currents of water pro-
duced by the cihary action of the cells that cover the
tentacles.

Of the animal corals that do not bear polyps there are
only two groups, and neither of these have many repre-
sentatives.

The living substance of the Foraminifera is not divided
up into a number of cell units, but is a continuous mass or
plexus of the vital stuff — protoplasm. There is no mouth,
no body cavity, and no tentacles, but at the periphery the
protoplasm spreads out into a complex web of filaments
which can capture and digest small organisms that come in
contact with it. The corallum is formed of a number of
adjacent chambers which are perforated by an immense
number of minute pores — the foramina.

There are only two or three sponges which can be called
Poriferan corals, and these will be described in a later chapter.
But, for comparison with other groups, it may be said here
that the Porifera are multicellular animals — without any of
the characters of polyps — which obtain their food by main-
taining a constant flow of water through an elaborate system
of canals and spaces in their body, certain cells of which
have the power of catching and digesting such organisms as
are nutritious.

The Plant corals all .belong to that division of the
Vegetable Kingdom which is known as the Algae. Most of
the Algae with which we are familiar are soft and flexible,
but two of the classes included in that division, namely, the
Rhodophyceae or Red Seaweeds and the Chlorophyceae or
Green Seaweeds, include genera which secrete a sufficient
amount of calcareous matter to render them hard and
resistant. As these coral Algae possess no mouths, holes, or
cavities that can be seen except with a high power of
the microscope, they were grouped together by the older
writers under the common name of " Nullipores," a name
which has now generally fallen into disuse.

The classification of corals adopted in this book may be
expressed in a tabular form as follows :

20 CORALS

I. Animal Corals.

A. Polyp-bearing corals.

1. Coelenterate corals.

(a) Madreporarian corals.

(b) Alcyonarian corals.

(d) Hydrozoan corals.

2. Polyzoan corals.

B. Corals that do not bear polyps.

1. Foraminiferan corals.

2. Poriferan corals.

II. Plant Corals.

A. Red Seaweed corals.

B. Green Seaweed corals.

Additional Note on the Nutrition of Corals

Although there can be no doubt that the polyp-bearing
corals can catch and digest living organisms for food as
described above, it seems to be highly probable that, in
many cases, this food is not the only source of their nutrition.

The canal system and often the polyps themselves of
many Coelenterate corals that live in shallow water are
crowded with little spherical cells {circa -oi mm. in diameter)
surrounded by a well-defined cell wall and bearing the char-
acteristic coloured vegetable substance Chlorophyll.

These cells are not coelenterate cells belonging to the
polyps but unicellular organisms, living under the protection
of their hosts, with their own independent reproduction and
nutrition. They should not be called parasites, for it is
evident that they do not irritate or injure the polyps. They
are of the nature rather of associates who live with the corals
for mutual help and protection.

This kind of association is called symbiosis, and the
unicellular organisms that take part in this symbiosis of
corals are called the Zooxanthellae.

The great importance of these organisms in the general

STRUCTURE AND CLASSIFICATION 21

physiology of corals cannot be fully estimated at present, as
there are many points in the relationship between the
svmbionts that are in need of further investigation ; but
some idea of the importance of the association may be
conveyed by a brief statement of the facts that are known
about a single example — the Millepora coral.

Millepora is a large massive or branching coral (see p. 145)
which is found in shallow water all over the tropical world,
and wherever it is found the superficial plexus of canals is
always crowded with zooxanthellae.

No specimen has yet been examined either in the East
Indies or the West Indies in which the zooxanthellae do
not occur in abundance. It is not a case, therefore, of an
infection confined to certain specimens or certain localities.

Moreover, it has been shown, in the case of Millepora,
that there is no stage in the life-history of the coral in
which it is free from this infection. The young egg cells in
the ovary, long before they reach full size and maturity, are
invaded by zooxanthellae from the surrounding tissues, and
thus, when the egg is fertilised and develops into a larva,
it is already provided with a full equipment of these sym-
biotic cells. ^

As no specimens of Millepora have yet been found without
the zooxanthellae, we cannot tell if this coral can manage
to exist without them, nor can we assert without experi-
mental proof that the association is of any benefit to it.

But similar cases of s3^mbiosis are known in other animals,
and in one of these — the symbiosis of the little flat worm
Convoluta with zoochlorellae — it has been shown experi-
mentally that the Convoluta is dependent on substances
formed by the zoochlorellae for at least an essential part of
its nutrition. 2

If, as seems highly probable, there is the same kind of
relation between Millepora and its zooxanthellae as there is
between Convoluta and its zoochlorellae, the holozoic method
of nutrition of the coral is supplemented by the holophytic
action of the chlorophyll-bearing zooxanthellae.

^ J. Mangan, Quart. Joitrn. Micr. Sci. ^2, 1909.
^ Gamble and Keeble, Quart. Journ. Micr. Sci. 51, 1907.

22 CORALS

The occurrence of zooxanthellae in the tissues of
Coelenterates of various kinds living in shallow waters is
very widespread, and in some cases where they are present
in unusual abundance the digestive organs of the polyps
seem to be degenerating.^

These facts and other considerations give strong support
to the hypothesis that the zooxanthellae play an important
part in the physiological processes of the reef corals.

The nutrition of the zooxanthellae is probably purely
holophytic, that is to say, it is a synthetic process carried
on by the action of chlorophyll in sunlight.

In order, therefore, that the action may be most effective,
the zooxanthellae should tend to collect in the superficial
canals, and they should be as free as possible from shadows
cast by surrounding objects.

This may account for the fact that has been commented
on by so many observers, that the coral polyps are usually
contracted in the day-time, and also for the fact that when
the digestive centres of the polyps are examined they are
usually found to be devoid of food.

The process of nutrition of corals may therefore be
continuous but alternating in character. In the day-time
the polyps contract so as to give the sunlight free access to
the zooxanthellae in the superficial canals, and in the night,
when chlorophyll action must cease, the polyps expand,
spread out their tentacles, and capture the animal food
which is as necessary for their sustenance as the starch that
is passed on to them by the zooxanthellae.

Whether this is the whole story of the nutrition of corals
it is difficult to say. That branch of science which deals
with the physiology of the lower animals is still in its infancy,
and it may be that in the light of new in\-estigations our
views on the nutrition of corals may be profoundly modified ;
still it is difficult to believe that the elaborate and highly
differentiated organs that the coelenterate polyps possess
does not indicate that animal food is an important, if not
essential, part of their nourishment.

1 Edith Pratt, Quart. Joiini. Micr. Sci. 49, 1905.

CHAPTER III

MADREPORARIAN CORALS

" Doch de Natiuir is in 't Element des waters zoo verwart, dat
men dingen vind, die men qualyk tot een van deze trappen brengen
kan, als of'er overblyfzels van den eersten Chaos in gebleven waren ;
want hier loopen levende, groeijende en minerale dingen alle onder
malkander, maakende planten die leaven, starren die groeijen, en
dieren die de planten nabootzen." — Rumphius, Rariteitkamer ,
Book I. chap, xxxvii., 1705.

When the Dutch naturahst Rumphius, at the end of the
seventeenth century, varied his remarkable investigations
on the plants of the Malay Archipelago by a study of the
corals at Amboyna and found it was difficult to determine
to what order of things they belonged, he exclaimed that in
the element of water there remains a survival of primordial
chaos.

To the naturalist of the present day, when he undertakes
the task of bringing into some kind of system the huge
numbers and variable forms of the Madreporarian corals
and the literature that deals with them, it may seem also
that here is the presence of a chaos which, if not primordial,
is at least as difhcult to unravel.

The Madreporaria are sometimes called the " Stony "
corals, but this popular name does not in the least help us
to distinguish a Madreporarian from any other kind of coral.
It is true that the driad corallum is hard and inflexible like
a stone and that, with a few rare exceptions, it is white,
but the same may be said of Millepora and many other corals
which are not Madreporaria. The only character that dis-
tinguishes them from other corals is the calyx (the calcareous

24 CORALS

Clip in wliich the polyps rest), with its radial septa, and
even this character is sometimes difficult to recognise or
define.

The Order provides the bulk of the corals of the world
at the present day. In variety of structure and in the
number of genera and species the Madreporaria exceed all
the other kinds of corals put together ; and it is in con-
sequence of this preponderance that some authors would
confine the expression " true corals " to those of Madre-
porarian origin and confer some other designation such as
"corallines" or "false corals" on corals of a different
Order. Such a plan, however, is historically unsound and
from a practical point of view^ inconvenient.

The Madreporarian corals may be arranged in various
ways. In former times, when very little or nothing was
known about the characters of the polyps, the classification
was based entirely upon the characters of the corallum. It
has been found, however, that such a classification leads to
the grouping together of corals that are not closely related
to one another, and, conversely, corals that are closely
related are, in such a system, widely separated.

A sound scientific classification should be based on a
knowledge of all the characters possessed by these animals
in both their hard and soft parts. Such a classification
will fluctuate as our knowledge, which is still very imperfect,
increases, and in that respect may cause some inconvenience,
but it is the only kind of classification that will express the
true relationship of these corals to one another.

The more empirical systems of classification, based on
the characters of the hard parts alone, have some general
utility and educational value, because in most cases such
characters are the only ones that are available for the
student at home, and the study of such characters must
form the introduction to this branch of science.

Proceeding on such a system, an examination of a good
collection of dried Madreporarian corals, such as may be
found in any large museum, shows that they may be arranged
in two groups.

In one may be placed those that exhibit a large number

MADREPORARIAN CORALS 25

of cup-like depressions for the polyps, and in the other,
those that consist of a single cup. The former are called
" Colonial " corals and the latter " Solitary " corals.

If the corals are then examined with a magnifying glass
it is found that, in some, the walls of the cups and other
structures are porous, and in others they are solid. The
former are called " Perforate " and the latter " Imperforate "
corals.

These two methods of grouping, however, are not similar,
for in both the solitary and in the colonial groups there are
examples of perforate and imperforate corals.

An examination of the base of a branch that has been
broken off a large corallum also shows that the tubes which
lodge the polyps are in some cases divided by transverse
partitions or " Tabulae," as in Millepora and Heliopora,
and in other cases are not so divided, and thus we can
speak of corals that are tabulate and corals that are not
tabulate.

All of these characters of the corallum may be of import-
ance in the description of the corals and in their classifica-
tion into families and genera, but it has been found that no
one of them affords a sufficiently trustworthy character for
the arrangement of the corals into large groups which are
intended to express genetic relationships.

For this purpose reference is made to the characters
that are showai by the anemone-like polyps which construct
the coralla, such as, the number and form of the tentacles,
the arrangement of the mesenteries, and the methods of
gemmation and fission. It seems probable that these
characters have undergone less change in the course of
evolution than the characters of the coralla, and that they
are, therefore, more trustworthy guides to genetic afftnities ;
but even these characters cannot alone serve the purpose
of a sound classification unless taken in conjunction with
the characters of the corallum.

In order that the student may become acquainted with
certain technical terms that it is necessary to use in the
description of the Madreporarian corals, it is best to
examine, in the first place, the structure of a specimen

26 CORALS

of a solitary imperforate coral. For this purpose the
English cup-coral, CcuyophyUia s}nithii, may be taken
(Figs. I, 2, 3, 4).

The wall of the cup, which is approximateh' circular in
section, is called the " Theca," and passing radialh' inwards

Fig. 2. — A group of four specimens of Carynphyllia smiihii and one specimen
(marked by a black ring) of Balanophyllia regia found at low water at Ilfracombe.
Nat. size.

towards the centre of the cup are a number of vertical
partitions which are known as the " Septa." From the
centre of the bottom of the cup there rises up into the
cavity a spongy dome-shaped calcareous mass formed of
some ten to twenty thin twisted plates, called the " Colu-
mella." From the outer border of the columella a number
of vertical plates similar to the septa, but more sinuous in

MADKEPORARIAN CORALS

form, extend outwards radially, but do not reach the walls
of the theca. These are the " Pali."

In the English cup-coral the septa are seen to project
as crests a short distance above the rim of the theca, and
are continued outside the rim as blunt ridges with granular
edges, called the " Costae " or " ribs " (Fig. 4). Below the
visible costae the outside of the theca is covered with a
chalky deposit which extends outwards over the spreading
ba-se of attachment, and this chalky deposit is called the
" Epitheca.'''

The polyp (see Fig. i, p. i5) which forms this corallum
is in appearance very much like a sea-anemone. In a

Fig. 3. — Diagram of a trans-
verse section through the cup of
a Caryophyllia. C, costa ; Co,
columella ; p, palus ; 5, septum ;
t, thecal wall.

Fig. 4. — Diagram of an external view
of a Caryophyllia to show the theca {t}
with its projecting costae and the epi-
theca let).

position corresponding with the centre of the cup there is
a slit-shaped mouth surrounded by a flat disc. At the
margin of the disc there are about fifty tentacles. Each
tentacle is provided with a number of wart-like batteries
of nematocysts and has a prominent white knobbed ex-
tremity, which is crowded with these stinging organs.

When the polyp is dissected it is found that the mouth
leads into a short throat called the " Stomodaeum," and
this communicates with the general body cavity. The
stomodaeum is bound to the body wall by a number of
vertical fleshy bands called the " Mesenteries," and con-
sequently the appearance of a coral polyp in transverse
section has a resemblance to a cart-wheel, the stomodaeum
representing the hub and the mesenteries the spokes (Fig. 7,

28 CORALS

p. ;^^). The number and arrangement of the mesenteries
are important characters in classification.

The fleshy substance of which the polyp is composed is
translucent and of a faint fawn colour, with a broad band
of brown colour on the disc surrounding the mouth, and red
or brown patches on the tentacles.

But, as in the sea-anemone, and, indeed, in most of the
Madreporaria, the colours of the living polyps are so variable
that the detailed descriptions of no two specimens from the
same locality would agree. De Lacaze-Duthiers, in his
description of some specimens from the coast of Brittany,
states that in one of his specimens there was a circle of
bright Veronese green at the margin of the disc, and in others
the walls were of brown or burnt sienna colour. In all
varieties, however, the colour scheme is of exquisite beauty
and of such delicacy of tone that it is almost impossible to
interpret it justly by art.

As an example of a colonial and imperforate coral Loplw-
helia prolifera (Fig. 5) may be taken. This coral, which is
found in deep water in many localities off the western coasts
of Europe, forms large tree-like growths with spreading
and sometimes anastomosing branches. On each of these
branches a number of cup-like prominences are arranged
alternately right and left, which show a series of radiating
septa like those of Caryophyllia. The prominences are
called the " Calices," and the common substance which
supports them is called the " Coenosteum." ^ A transverse
section of the coenosteum shows a thick imperforate wall
and an axial cavity divided into a number of chambers by
radiating bands of coral substance which meet at a hub
in the centre. Further investigations would show that
these radiating bands are continuous with the septa of the
calyx immediately above the section of the branch that has
been examined, and that the branch has been formed by
a process of budding and subsequent growth of a new

^ Many writers on corals use the term " Coenenchym." This is
etymologically and historically inaccurate. The word coenenchym was
introduced by Milne- Edwards and Haime for the fleshy substance between
the polyps in Alcyonaria (Hisloire natuyelle des coralliaires, 1S37, vol. i.
p. 29).

'^ N W^

9 4 i 4f'

f ^

Fig. 5. — -Lophohclia prolifera From the Bay of Bisca}', 400 fathoms, i nat. size.

MADREPORARIAN CORALS 29

polyp and calyx from the margin of the calyx of the youngest
terminal calyx of the branch, followed in turn by the forma-
tion of a new polyp and calyx on the opposite margin of the
former when it has reached a later stage of growth. This
alternate right and left budding gives the younger branches
of a large colony a curious zigzag appearance, but in the
older branches the angles become smoothed out by the
continuous growth of the coenosteum until they appear
to be perfectly straight.

The study of this method of growth in Lophoheha is
necessary in order to understand that the calyx of a coral
corresponds with only a part of the corallum of a soHtary
coral like Caryophylha. The lower part of the theca of
the solitary coral is represented by that part of the branch
which extends from the calyx to the level of the next calyx
on the opposite branch. In other words, it might be said
that this colony is formed by the coral polyps growing on
one another's shoulders.

In other colonial corals it is not easy or not possible to
demonstrate that the colony has been formed in this way,
and consequently the coenosteum or matrix which bears
the calices appears to be entirely communal in origin and
function.

In another colonial imperforate coral, Ociilina, for ex-
ample, which is usually placed in the same family as Amphi-
helia, the calices do not project above the general surface
of the coenosteum, and are not arranged alternately right
and left, but seem to be arranged spirally or scattered about
irregularly on all sides of the branches, and when the branch
is examined in transverse section there is no axial series of
chambers such as we find in the Lophohelia branch.

In the family Astraeidae or Star corals, which are usually
placed next in order to the Ocuhnidae, the cahces are more
crowded together, so that the amount of coenosteum between
them is reduced to small dimensions (Galaxea), or the
calices come into such close juxtaposition that there is little
or no coenosteum at all.

Before passing on to the complex forms of corallum
produced by complete and incomplete fission or by perfora-

30 CORALS

tion, reference may be made to the polyps of one of the
colonial corals that has just been described and their rela-
tion to the corallum.

The polyps of Lophohelia, according to de Lacaze-
Duthiers, are provided with a crown of tentacles of various
lengths corresponding in number with the septa (about
twenty in a full-grown polyp) ; the mouth in the centre of
the disc is slit-shaped, the slit being parallel with the axis
of the branch. The outer wall of the polyp flows over the
rim of the calyx, and is continuous with a thin laver of
fleshy substance that covers the coenosteum and brings
the polyps into organic continuity with one another. This
communal lining substance may be called " Coenosarc."

In life the polyps and the coenosarc are so remarkably
transparent that the details of the coral structure can be
seen through them, but nevertheless they do exhibit a faint
yellow or orange colour, which is accentuated on the disc
round the mouth. The tentacles are also transparent and
faintly yellow in colour, dotted with little white spots, and
terminating in a white conical point. All these soft parts
of the Lophohelia colony are situated above the hard parts
— there are no canals or other living tissues that penetrate
into the coenosteum or into the septa or walls of the calices,
and consequently, when the colony dies, the coenosarc peels
off the coenosteum and the polyps become detached from
their calices.

This is in marked contrast to what is found in perforate
corals in which both polyps and coenosarc are firmly locked
into the corallum by canals and strands of tissue that pass
through the perforations.

The classification of the Madreporarian corals is still in
a very unsatisfactory and unsettled condition, owing, in
part, to the very limited knowledge we possess of the
structure of the coral polyps, and in part to the wide range
of structure that the group exhibits leading to interdigita-
tion of the families and sub-orders.

In some of the Madreporaria, such as the genera Madre-
pora itself, Porites, Pocillopora, and Seriatopora, the polyps

MADREPORARIAN CORALS

possess only twelve tentacles and twelve mesenteries, but
in the great majority of the genera the number of tentacles
and mesenteries is very much greater than twelve when the
pol3^ps have reached their full size.

The number of septa in a calyx does not always corre-
spond with the number of mesenteries in the polyp that
formed it ; but, generally speaking, when there are only
twelve mesenteries there are only twelve or six septa. In
the calices of polyps with a large number of mesenteries
there are usually a large number of septa.

It has been suggested, therefore, that, in the first place,
the Madreporarian corals with polyps that have twelve
mesenteries should be placed in one sub-order, and those
with more than twelve mesenteries in another. There are
some difficulties, however, in accepting this division of the
group at present, as our knowledge of the anatomy of the
polyps of so many genera is imperfect, and a rearrangement
of our system of classification on imperfect knowledge would
be confusing and unsatisfactory. The best plan is to
accept the classification that is in general use as regards the
families, a classification which is based on the characters of
the corallum, and rearrange the order of these families on
the lines suggested by our knowledge of the anatomy of the
polyps. 1

The arrangement suggested is as follows :

Group A. — Polyps with more than twelve mesenteries.

Family i.
Family 2.
Family 3.
Family 4.
Family 5.

Turbinoliidae.

Oculinidae.

Astraeidae.

Fungiidae.

Eupsammiidae.

^ For further information on the classification of the Madreporaria the
student should consult the beautifully illustrated memoirs by T. Wayland
Vaughan, entitled " Recent Madreporaria of the Hawaiian Islands and
Laysan," Smithsonian Instiattion Bull. 59, 1907, and " Shoal-water Corals
from Murray Island," etc., Carnegie Publications of Washington, 1918. In
these memoirs reference is given to other papers which are necessary for the
identification of specimens. P. Martin Duncan's A Revision of the Families
and Genera of the Madreporaria, published in 1884, is stiil-rcrf;:;ra9e4ltial
importance, and should be referred to. .^^*!^icV « VJ^ /

'^ "--^

^\'-

CORALS

Group B. — Polyps with twelve mesenteries.

Family 6. Seriatoporidae.
Family 7. Madreporidae.

These families include most of the recent Madreporarian
corals, but there are still some recent corals, such as Pyro-
phylha, (iuynia, Bathyactis, etc., and many fossil corals
which cannot, at present, be placed in any of them.

Before proceeding to a systematic description of a few
representative genera of each of these
families it is necessary to refer briefly
to the arrangement of the mesenteries
of the Madreporarian polyps and their
relation to the septa.

It has been found that in the
development of the Madreporarian
coral polyp there is a stage when
there are twelve mesenteries, and
that these twelve mesenteries have
certain definite characteristics.

The mesenteries are thin laminae
of soft fleshy substance passing from

cnteries (protocnemes) ; DS, i\^q body Wall tO the StomodaCUm Or
the directive septa ; St, the c ^

throat. Some of these reach the
stomodaeum, others do not.

From each end of the stomodaeum,
which is sometimes round and some-
times oval in section, a pair of mes-
enteries pass to the body wall, called the Directive mesenteries
(Fig. 6, III-IV), and in each lateral space between the pairs
of directive mesenteries there are four mesenteries, making
a total of twelve in all.

These mesenteries are called the Primary mesenteries or
Protocnemes, and it may be added they are formed in bi-
lateral pairs, that is to say, at the time of their appearance
one member of a pair corresponds with the other member
on the opposite side of the stomodaevmi. The order of
sequence of these mesenteries is indicated by the numbers
I-VI in the diagram.

Fig. 6. — Diagram of a
transverse section of a
Madrcporid calyx to show
the relation of hard parts
(thick lines) and soft parts
(thin lines). I-VI, the mes-

stomodaeum ; III-IV, the
directive mesenteries. On
the right side of the diagram
the section is taken through
the stomodaeum ; on the
left, below it.

MADREPORARIAN CORALS 33

In the families of corals belonging to Group A additional
pairs of mesenteries are added to the primaries, but these
are unilateral pairs, the two members of a pair being close
together on the same side of the stomodaeum.. These uni-
lateral pairs of mesenteries are called the Secondary mesen-
teries or " Metacnemes." In the diagram (Fig. 7) that has
been drawn to illustrate this arrangement eighteen unilateral
pairs — metacnemes — have been drawn, but it must be noted
that in most of the corals belonging to Group A there are
more than eighteen metacnemes, and in many cases a
very large number. There is one point
also which is of particular interest
and importance in the arrangement
of these mesenteries. The pairs of
metacnemes appear in the spaces be-
tween the lateral protocnemes, but no
metacnemes are ever found in this
group in the spaces between the direct-
ive mesenteries.

The result of this arrangement is that Fig. 7.— Diagram of

1 J 1 1 J 1 j_ 1, the mesenteries of the

whereas the lateral protocnemes may be Astraeid polyp Manicina,,
separated from one another in a large showing eighteen pairs

, , J 1 r • £ of metacnemes. II 1-3.

polyp by a great number of pairs of nii-6. After Duerden.
metacnemes, the directive mesenteries

always stand side by side and can be recognised as the
directives throughout life..

But this is not the only character by which the directive
mesenteries can be recognised.

One of the functions of the mesenteries is to support
the important longitudinal muscles which cause the retrac-
tion of the polyps, and the position of these muscles can
be seen in a transverse section of a polyp as a series of
ridges on one surface only of the mesenteries. In the cases
of the directive mesenteries these ridges are on the surfaces
opposed to each other, that is to say, they face outwards
(see diagram 6, III-IV), whereas in the other mesenteries
the muscle ridges face inwards (see diagrams 6 and 7).

This feature of the directive mesenteries is of some im-
portance in the study of the anatomy of the Astraeid corals

CORALS

in particular, because the polyps of some of the corals
belonging to this family appear to be entirely devoid of
directive mesenteries, and this fact can only be explained
by their method of asexual reproduction.

The different kinds of asexual reproduction in the
Madreporarian polyps may be arranged in two categories :
reproduction by gemmation or budding and reproduction
by fission or division into two. Reproduction by gemmation
may be intercalicinal when the buds arise from the coenosarc
between the calices, epicalicinal when they arise from the
outer wall of the calyx, or intracalicinal.
The buds produced by all these methods of
gemmation always show throughout life
two pairs of directive mesenteries. In
reproduction by fission in the Astraeid
corals the mouth and stomodaeum con-
strict in the middle to form two mouths
and two stomodaea (Fig. 8), and when the
body wall of the polyp follows suit the
metacnemes II 2 take up a position opposite
to the directive mesenteries 1 4 and 1 5 in
the resultant polyps, and thus each of
these daughter polyps has only one pair
of directive mesenteries. \\'hen these
daughter polyps are large enough to divide
they each give rise to one with one pair of directive
mesenteries and one with none.

And thus it comes about, by a continuation of this
process, that in a large colony of Astraeids the directive
mesenteries appear to be absent in all the polyps, although
theoretically there should be somewhere in the colony two
polyps each with one pair.

In the families belonging to Group B, the directive
mesenteries and the other protocnemes are formed as in
the corals of (iroup A, but, as they are not succeeded by
any series of metacnemes, the normal number of mesenteries
in a full-grown polyp is twelve.

In the process of fission in the genera Madrepora and
Porites belonging to this group a new set of twelve mesen-

FiG. 8. — Diagram
to show a stage in
the division by fis-
sion of the Astraeid
polyp Manicina. I 3
and 1 4 the directive
mesenteries. After
Duerden.

MADREPORARIAN CORALS

teries appears in the space between two directive mesenteries.
Thev appear in regular sequence (Fig. lo, A, B, C, D) in
bilateral pairs until the full number of twelve is reached.
Then the mouth and stomodaeum divide by constriction
as in the Astraeid, and when the polyp itself constricts two

Figs.

Fig. 9. Fig. iu.

9 and 10. — Diagrams of sections of Poritcs to show the new set of

Protocnemes is formed in space between the directive mesenteries III, III. In
Fig. 9 one pair, A, A, has been added, in Fig. 10 four pairs. After Ducrden.

pairs of directive mesenteries are formed for each daughter
polyp by the mesenteries marked IV and / on one side and
III and a on the other, that is to say by one old directive
mesentery and one new one in each pair (Fig. ii).

Thus it comes about that in these two genera, although
asexual reproduction is by fission
everv polvp in a large colony
has two pairs of directive mes-
enteries.^

The relation of the hard
calcareous septa of the coral
cup to the soft fleshy mesenteries
of the coral polyp which forms
it is a matter of considerable
importance for the proper under-
standing of coral anatomy. The
septa are alwavs formed in the spaces between the mesenteries
and never in the substance of a mesentery (Fig. 6, p. 32),
and, as the septa do not always correspond in number with
the mesenteries, the septa of the dried coral afford no trust-

'■ J. E. Duerden, " West Indian IMadreporarian Polyps," Mem. Xat.
Acad. Sci. Washington, vol. viii., 1902.

Fig. II. — Diagram to show a
stage in the division of a polyp of
Porites. Lettering as in Figs. 9 and
10. After Duerden.

36 CORALS

worthy evidence concerning the mesenteries of the living
poh'p. It may be said, however, that wlien there are six or
twelve septa there are twelve and usually not more than
twelve mesenteries, and that when there are more than
twelve septa there are alwa^^s more than twelve mesenteries.
In the method of development of the septa there appears to
be a remarkable uniformity in corals belonging to widely
separated families ; but in view of the fact that our know-
ledge of coral embryology is still very limited, it would not
be right to assume that there are no exceptions to what
appears, at present, to be a general rule.

When in the development of the polyp of a solitary
coral or the first polyp of a colonial coral the twelve primary
mesenteries (protocnemes) have been formed, six septa
appear simultaneously in the spaces between the mesenteries.
Two of these six septa are always found in the spaces between
the directive mesenteries and may be called the directive
septa, and the others in alternate intermesenteric spaces.
These are followed by another six septa situated in the
remaining six intermesenteric spaces.

Twelve septa are thus formed, and, in conformity with
the terminology of the mesenteries, these twelve primary
septa may be called the " protosepta."

In some cases (Astroides, Balanophyllia, etc.) the twelve
protosepta appear simultaneously, but there are many
reasons for believing that the former method of septal
sequence is the more primitive.

The formation of the metasepta in the corals of Group
A follows very closely the formation of the metacnemes, a
single septum appearing in the space enclosed by a uni-
lateral pair of metacnemes. But in some cases septa are
also formed in the spaces between the unilateral pairs of
mesenteries, and thus a distinction has been drawn between
the septa that are formed inside a pair of mesenteries (Ento-
septa) and those that are formed between these pair (Ecto-
septa). Further discussion of the very complex problems
of septal sequence in recent and fossil corals would require
more space than can be assigned to the subject in this book.

With these preliminary remarks on the points of structure

MADREPORARIAN CORALS 37

of these corals, which are essential for the understanding
of the classification, we may now proceed to the study of
the families.

Family i. Tureinoliidae

The corals included in this family are mostly solitary
in habit, and are either attached to rocks, shells, and other
foreign objects, or in some cases rest freely in or on a sandy
sea-bottom.

They may be distinguished from the solitary corals
belonging to the other families by being imperforate and by
having septa which liave usually smooth surfaces ; but if
the septa are armed with spines or tubercles, they are not
joined together bv bars (Synapticula) of coral substance as
they are in the Fungiidae.

From the solitary and imperforate corals of the family
Astraeidae, the Turbinoliidae are distinguished by the
occurrence in the former of dissepiments or tabulae which
shut off the living polyp below from the original base of
the calyx, whereas in the latter the spaces between the
septa pass right down to the base of the calyx.

The British cup-coral CaryopJiyllia smithii has been
described on p. 26. It is found at low tide attached to
the rocks near Ilfracombe, on the breakwater at Plymouth,
and probably in other localities on the coast of Cornwall
and Devon. It is also found at Roscoff on the coast of
Brittany and on the coast of Norway. Other species of
the genus Caryophyllia occur in the Mediterranean Sea,
and the genus seems to have a pretty wide distribution in
shallow water.

The only other corals belonging to this family that have
been found on the British coast belong to the genera Para-
cyathus and Sphenotrochus They occur only in deep
water off the Atlantic coasts and may be regarded as
among the rarities of our marine fauna.

The genus Paracyathus, however, seems to be very
abundant in some other localities, and requires a few words
of description.

Paracyathus. — A large number of specimens of Para-

38 CORALS

cyaf/iits ciU'dtiis were obtained a little while ago attached
to the telegraph cable in the Persian dulf. In form they
are not unhke the Caryophyllias, but of a larger size, having
diameter of half an inch or more at the margin.

When the coral is carefully studied, however, many
features can be noticed in which this coral differs from
Carvophyllia. These may be referred to here as an example
of the kind of characters that can be used for separating
genera and for the identification of specimens.

There is a broad base of attachment as in Carvophyllia
which adapts itself to the surface of the support. Outside
the cup the costae may be seen extending from the base
upwards as delicate ridges. They are not, therefore,
covered up by a chalky " Epitheca " at the base as they are
in Caryophyllia. The septa are very numerous and covered
with minute granulations arranged in a series of longitudinal
and radial row^s, in contrast to the smooth septa of Caryo-
phyllia. The inner margins of the septa exhibit a number
of large nodules which represent the pali, and these pass
imperceptibh' into the central depressed columella, which
is similarly covered with nodules. In Caryophyllia the pali
and the columella are quite distinct. Such a technical
description is difficult to follow unless the specimens are in
the hand, but sufficient has been said, perhaps, to indicate
that differences in structure such as these, when found to
be constant in a large number of specimens of both corals,
are sufficient to justify their separation as distinct genera.

Paracyathus cavatiis is also found in the Indian Ocean,
and other species of the genus are found in the Mediterranean
Sea and elsewhere.

Heterocyathus. — The genus Heterocyathus presents
us with some features of special interest. It is a small coral
about one-third of an inch in height which is found in large
numbers at depths of 20-40 fathoms of water off the coast
of Natal, in the Persian Gulf, and other localities in the
Indian Ocean. An important difference between this coral
and those belonging to the family that has been described
is, that the free edges of some of the septa meet and fuse,
forming triangular chambers in which septa of a lower

MADREPORARIAN CORALS 39

order are placed. In other respects it approaches Para-
c\'athiis in structure, having well-marked costae and a
nodular columella. The special point of interest, however,
is that the coral always lives in association with a small
worm (Aspidosiphon) belonging to the Order of the Gephyrea,
and this is indicated in the dried coral by a small smooth
round hole at the side of the base through which in life the
worm protrudes.^

These corals seem to occur always on sandy bottoms,
and have no disc of attachment or other means of fi.xing
themselves to rocks, large shells, or other objects of sufficient
weight to resist the flow of water.

The association with the worm is an ingenious arrange-
ment to prevent the coral being overturned and smothered
in the sand, and to ensure the maintenance of an upright
position in which the tentacles of its polyp can catch the
floating and drifting organisms on which it feeds, for the
Gephyrean worm feeds in the sand and thus acts as a kind
of muscular root always ready to drag the coral upright
again if it loses its balance.

The origin of the association can be seen in very young
individuals or by making vertical sections of a full-grown
specimen. The young worm begins life by sheltering in a
small Gasteropod shell {e.g. Cerithium) like a Hermit Crab.
The coral larva settles on the outside of the shell by an
ordinary base of attachment, and as the coral grows and the
base extends it surrounds the shell, leaving only a hole
through which the worm can protrude. Growth of the
coral does not stop when the shell is completely surrounded,
but continues in all directions to form a smooth rounded
base perforated on one side by the worm tunnel in the
coral substance, which can be traced from the outside to
the mouth of the shell. The size and shape of the shell
on which the coral larva starts life vary considerably and
cause many variations in the subsequent shape of the
adult coral. This has led to the splitting of the genus
into a large number of quite unnatural species, and subse-
quently to the amalgamation of these species into one or

^ As in Heteropsammia, Fig. 32, p. 79.

40 CORALS

two species wiiicli are recognised to be highly variable in
form.

More interesting than the settlement of this difficult
and highly controversial species question, however, would
be the discovery of the determining cause of the association
of the worm and the coral. It seems highly probable that
if the coral larva settles down on a little shell that has no
worm in it, it could not long survive, for it would soon be
rolled over and smothered in the sand either by the action
of the currents of water or by any fish or crab that passed by.
Does the coral larva, therefore, select shells already
inhabited by a worm or does it simply trust to chance ?
In the latter case, thousands must die for every one that
survives. It may be, however, that there is a kind of
unconscious selection, the larva finally settling down onlv
on a shell whose stability — due to the presence of the worm
— has been tested.

The Heterocyathus is not the only coral associated with
this or a closely related worm. The same thing is found in
the perforate Eupsammiid coral Heteropsammia, occurring
in the same seas and under similar conditions.

Desmophyllum. — The largest of the Turbinoliid corals
is Desmophyllum crista-galli, which attains to a height of
4 or 5 inches and a diameter of li inches at the margin of
the calyx. It has been found in deep water in the Atlantic
slopes off the British coasts and in other localities. A giant
specimen of this species, 5^ inches in height, was found by
the Challenger expedition in 345 fathoms of water off the
coast of Patagonia. The living polyp of this genus has
been studied and drawn by de Lacaze-Duthiers.

Flabellum. — The widely distributed, and in some
localities very abundant, genus Flabellum is usually placed
in a separate subdivision of the family on account of the
peculiar formation of the wall of the calyx.

Most of the specimens belonging to the genus are not
round, but oval in section, being, as it would seem, laterall\-
compressed. The longest of the diameters is in the plane
of the directive septa. When viewed from the side, Fla-
bellum has the shape of a fan with the handle sharply

MADREPORARIAN CORALS

broken off. The outer wall does not show any trace of
costae, but there is a series of more or less well-marked
transverse lines of growth. The principal peculiarity of
the genus, however, is that the polyp is entirely restricted
to the inside of the calyx. It does not overflow, as in many
of the corals, so as to cover the whole or the upper part

of the outside of the

calyx with its soft
living flesh. As the
outer wall of the calyx
is thus wholly exposed
to the sea - water, it
frequently forms the
support of worm-tubes,
polyzoa, barnacles,
and foreign bodies of
various kinds. The
process of formation of
the wall of the calyx
in Flabellum appears
to be of a different
type from that in the
other Turbinoliidae, as
shown by the absence
of costae and the pre-
sence of foreign bodies,
and it is therefore
usually regarded as an
epitheca and not as a
true theca.

In the younger
stages of its life the base comes to a blunt point, terminating
in a small disc for attachment to a shell or rock, but when it
has attained to a certain size this point is broken off sharply,
leaving an oval scar at the base in which the septa are exposed.

After the coral has broken off its base of attachment
in this way, one or more pairs of wing-like processes may be
formed on the edges of the epitheca, or in some cases hollow
root-like tubes grow from the scar.

Fig. 12. — Flabellum rubrum. The upper
figure shows the cavity of the calyx and the
septa. The lower figure is a side view showing
the lateral processes and the scar at the base.
Nat. size.

42 CORALS

The latter are clearly for the purpose of attachment to
some foreign object, and the former may act as additional
supports for the specimens that are imbedded in sand and
mud. Specimens taken from the same locality are extremely
\'ariable as regards both wings and roots, and it seems
probable that these structures are formed in response to the
conditions of the immediate environment and cannot be
regarded as of any generic or specific importance. A few
specimens have been found which were attached to a rock
or shell by the side of the epitheca, and such specimens
usually exhibit additional abnormalities of form.

Family 2. Oculinidae

The corals of this family form large imperforate branch-
ing colonies bearing numerous calices, separated from each
other by considerable intervals of coenosteum.

As in all the colonial corals, there is immense variety in
the size, manner of branching, occurrence of anastomoses,
and the distribution of the calices. In recent Oculinidae,
however, although the main stem may be nearly an inch
in diameter, the branches are usually slender, | to | inch
in diameter, and terminate in blunt extremities. Massive
and encrusting forms of colonies are rare.

The genera Amphihelia and Lophohelia belonging to
this family are of special interest, because they are the only
large colonial corals that are found in British seas. They
are widely distributed in deep water in the North and
South Atlantic, in the Mediterranean Sea, in the East and
\\'est Indies, and elsewhere. They come within the British
fauna off the west coast of Ireland and off the coast of
Cornwall.

A general account of the structure of Lophohelia has
been given on p. 28.

Amphihelia. — The genus Amphihelia resembles Lopho-
helia very closely in its mode of growth and ramifications,
but is said to differ from it in having a shallower depth of
calyx, in a greater regularity of the septa, and in the presence
of a true columella. In Lophohelia, moreover, there may

MADREPORARIAN CORALS 43

exist laminae of calcium carbonate — called the dissepiments
— which pass transversely across the inner septal spaces in
the depths of the calyx, shutting off the upper spaces where
the living polyp tissues are found from the dead coral below ;
and in some cases true tabulae occur. In this respect the
calices of Lophohelia approach in structure the calices of the
next family of corals — the Astraeidae — whereas Amphihelia,
in retaining the open spaces between the septa right down
to the base of the calyx, resembles the Turbinoliidae and the
other genera of the Oculinidae.

There is, however, so much variation in all these char-
acters in both genera, that it is sometimes difficult to deter-
mine without most careful examination whether a given
specimen is an Amphihelia or a Lophohelia. This difficulty
is increased by the frequent occurrence in specimens obtained
from some localities of the natural grafting of the two genera.
Specimens are found of which one branch may be a true
Lophohelia and the others Amphihelia, and when the place
where the branches join is carefully examined, even in
sections, no boundary line can be distinguished to indicate
where the Lophohelia tissue begins and where the Amphi-
helia tissue ends (Fig. 13). Such grafts might readily lead
to a hasty but probablv erroneovis conclusion that the two
forms are not distinct, but are only environmental variations
of the same genus and species.

It is not known how this grafting takes place, but as
de Lacaze-Duthiers ^ remarks : "La puissance blasto-
genetique est des plus actives dans cette espece {i.e. Auiphi-
hclia oculata). Tout ce qui touclie a une partie du zoantho-
deme vivant est fixe, retenu et reconvert par le sarcosome
d'abord, et plus tard par le tissu sclereux." Worms, molluscs,
bryozoa, and other living things are caught, enveloped by
the soft coenosarc, and subsequently covered by the hard
coenosteum, and it seems probable, therefore, that when a
Lophohelia larva settles on a branch of Amphihelia, or vice
versa, and begins to grow, the base of the young colony
becomes, in like manner, entirely submerged in the growing

1 H. de Lacaze-Duthiers, " Zoanthaires sclerodermes," Arch. Zool.
Expev., 3", v., 1897, p. 143.

44 CORALS

coenostenm of the host, and is thus cjiven a firm attachment

Fig. 13. — In the lower part of the tigurt' is situ a branch oi Lophoht-ha showing
two calices on opposite sides. In the upper part of the figure the Lophohelia is
seen in blastogenic fusion with an Ainphihelia with much smaller calices. Nat. size.

for the subsequent growth of the colon}-. The remarkable

MADREPORARIAN CORALS 45

feature of the case is that, owing to the similarity in minute
structure of tlie coenosteum of the two genera, all trace of
the line of fusion is lost.

In both these genera anastomoses of the branches,
formed in the same manner by the grafting of one colony on
another or of one branch with another, frequently occur,
giving rise to great tangled masses of coral branches, with
various kinds of worm-tubes and shells deeply imbedded in
them (Fig. 5, p. 28).

To write an accurate description of such a mass would
require a great deal of time and patience, as it might consist
of three or four species, each showing a great range of varia-
tion in the size of the calices and the characters of the septa
and columella, all of which would have to be carefully
studied before an approximate estimation of the number of
individual corals that have taken part in the composition
of the masses could be made.

The only account of the living polyps of these two genera
that we possess is that of de Lacaze-Duthiers. In both
genera the living tissues are very transparent, but show a
pale yellow colour, which is more pronounced round the
mouth and on the oral disc. The tentacles correspond in
number with the septa, and vary in size according to the
order of the septa above which they are situated, the tentacles
above the primary septa being larger than those above the
secondary septa, and those, above the secondary septa larger
than those above the tertiary septa. They have a pale
yellow colour and are speckled with white spots representing
nematocysts or groups of nematocysts, and at the extremity,
which is pointed, these spots are so numerous and closely
grouped together that the tentacle seems to have a bright
white tip. Minor differences between the genera observed
by de Lacaze-Duthiers are, that in Lophohelia the tentacles
are relatively shorter and thicker than in Amphihelia, and
that the size of the tentacles in the former is more irregular
as regards the order of the septa than it is in the latter.
Fowler has also pointed out that in Lophohelia there are no
directive mesenteries, but that in the Amphihelia they are
present.

CORALS

OCULIXA. — The genus Oculina belonging to this family
is found in a few fathoms of water in the warmer tropical
seas. Like the other genera that have been described, the
corallum is sparsely branched, and sometimes shows anasto-
moses and fusions of the
branches.

The coenosteum is very
hard and solid. The calices
are relatively more numer-
ous and very shallow, and
are usually arranged in
steep spiral rows on the
branches. The rims of the
calices project a little from
the surface, giving it a
warty or verrucose appear-
ance. The number of septa
varies, but is usually about
twenty-four, and standing
opposite the free edges of
the principal orders of the
septa there are pali. The
columella is variable, but
frequently consists of a few
short pillars very similar
in appearance to the pali.

Family 3. Astraeidae

The familv of the As-
Fig. i4.-Ocuiina. A small piece of a tracidac or Star-corals is,

branch of a large colony. Nat. size. _ _

in respect of variety of
structure and number of generic forms, the largest and most
difficult of all the families of the Madreporaria.

The family pla\'ed an important part in building up the
coral reefs of the Jurassic, Cretaceous, and early Tertiary
times, but in later Tertiary and in recent times, although
still very abundant in some localities, they take a second
place in reef-building powers to the more vigorous and

MADREPORARIAN CORALS 47

rapidly growing genera of the younger families — the Madre-
poridae and Poritidae — of the Perforate corals.

Most of the Astraeidae are colonial corals, and give rise
by fission or gemmation to large heavy rocks of limestone,
usually spherical or lobed in form, and rarely, among recent
genera, dendritic in growth, and, if dendritic, never dividing
up into pointed terminal branches.

The calices are usually set close together, and in many
genera are actually in contact with one another, so that there
is little or no coenosteum between them. The septa are
numerous, and may be entire and smooth as in the " Astrsees
inermes " of Milne-Edwards and Haime, or dentate, spined,
or ragged as in the " Astrsecs amies " of the same authors.
But the septa nev^er meet and fuse together as they approach
the centre of the calyx as in some of the Eupsammiidae (see
p. 75), nor are they connected together by synapticula as
in the Fungiidae.

One of the most important features of the family is that
as the cah'x increases in length by upward growth at the
surface, the lower part of the cavity of the calyx becomes
shut off from the upper by calcareous structures, for which
w^e may use the general term " Endotheca." The poh'ps
and other tissues of the coral are entirely confined to the
surface and to the cavities of the calices down to the level
of the endotheca. It is the presence of endotheca which is
the only character to distinguish some genera of Astraeidae
from genera of Oculinidae and of Turbinoliidae, which in
other respects are very similar to them.

There is unfortunately some confusion in the use of
the technical terms that are employed for the different
kinds of endotheca, and it is difficult to give any terms
a very precise definition owing to the great variety of
form that the endotheca assumes, but the diagrams in
Fig. 15 will show the three principal varieties that are
found.

When the endotheca is in the form of transverse plates,
the plates are called Tabulae ; when it is in the form of
irregular laminae, the laminae are called Dissepiments ;
when it is more or less of granular consistency, filling up the

CORALS

spaces and sometimes fusing into solid bars and plates, the
substance is called Stereoplasm.

Galaxea. — The genus Galaxea, widespread on East
Indian tropical reefs, is a genus which can be easily identified
(Fig. i6). The general form is very variable, as in all the
genera of the Astraeidae, but the colony is frequently dome-
shaped or hemispherical, sometimes throwing out thick lobes
or branches, but never being completely dendritic.

The calices stand up from the free surface of the coeno-
steum as vertical cylindrical columns 5-10 mm. in height.
Each calyx is about 5 mm. in diameter, and separated from

its neighbours by a

Fig.

distance of about the
same measurement.

There are twenty-
four conspicuous
septa, twelve large
and twelve small,
alternating with one
another, and in some
calices there may be
seen, in addition,
twenty - four minute
septa between the

15.— Diagrams to illustrate the three mOrC COnspicUOUS
principal kinds of endotheca. A, tabulae; B, QT->pc TVip sfnta are
dissepiments ; C, stereoplasm. ' ^

exsert, that is to say
thev project upwards, above the lip of the calyx wall. There
is no true columella, but the larger septa are connected at
the base of the cup by dissepimental bars or trabeculae.
There are no pali. The surface of the septa is rough, but
is not armed with spines.

The common coenosteum lying between the bases of the
calices, which in this case is called the " Peritheca," is
marked bv a number of small blister-like swellings, and is
therefore technically called " Vesiculate."

In certain parts of the colony where growth is active,
such as the free edges or the ends of the lobes, a number of
small calices can be seen. These small calices have been

MADREPORARIAN CORALS 49

formed by the young polyps which have arisen as buds
from the peritheca. This is a very important point to
grasp if the very difficult and perplexing problems of the
classification of the Star-corals are to be understood. For
in every modern system of classification great stress is

Fig. 16. — Galaxea caespitosa, Malay Archipelago. Nat. size.

laid on the method of asexual reproduction found in the
colonies.

In Galaxea and many others this method of reproduction
is by budding or gemmation, and by that particular kind
of gemmation which is known as perithecal or intercalicinal
gemmation. The particular method of gemmation is not

50 CORALS

always constant, and, in some forms of Galaxea even, some
of the buds may arise from the outer wall of the calyx, a form
of gemmation that is called " Epicalicinal " or " Epithecal."

\Mien the Galaxea colony is alive, the soft flesh covers
the whole surface of the colony as with a mantle. It is not
locked into the corallum, as it is in the Perforate corals, by
a system of canals perforating the subjacent hard parts.
When the colony is killed, therefore, parts of the tissues as
they become hardened are often detached, or may be
detached with a little manipulation with needles, showing
that this flesh is entirely superficial.

The polyps show a crow'n of twenty-four simple tentacles
surrounding a centrally placed mouth, and there are twenty-
four mesenteries, of which two pairs are directive mesenteries,
in the fully developed condition.

The colour of the living polyps probably varies in
different localities, but in a specimen observed by the author
on the reefs of Celebes they were of a bright emerald green
colour, the expanded colony, as seen through the clear water
in the sunshine, being one of the most brilliant of the many
beautiful corals of the locality.

Favia. — The second type which may be taken to illus-
trate the structure of the Astraeid corals is a genus which
is, perhaps, most correctly called Favia (Fig. 17). But in
this case, as in many others of the same family, the student
will find great difficulty in coming to a definite conclusion
as to the correct generic name of a specimen owing to the
differences of opinion expressed by those whose detailed
study of Madreporarian structure has given them the right
to be regarded as authorities on the subject. Apart from
questions of the law of priority in nomenclature, there is
the difficulty in this group arising from the fact that there
is so much variation in the species, and there are so many
closely related genera that many perplexing examples occur
of intermediate or overlapping species and genera. The
consequence is that the old genera have been split into
several new genera and the new genera reunited under the
old generic name in a way that has made it very difficult
to maintain an accepted or acceptable nomenclature.

MADREPORARIAN CORALS

Oken's genus Favia was established in 1815 for a section
of the older genus Astrea of Lamarck, and it includes species
of corals that have been described under the generic names
Orbicella, Heliastraea, Plesiastraea, etc., etc.

The corals of this genus are usually hemispherical or
almost spherical in shape, without lobes or branches but

Fig. 17. — Favia. A small specimen. Xat. size.

sometimes encrusting in habit. The surface of the coral
consists of a large number of close-set calices about 10 mm.
in diameter which project but slightly above the general
level of the scanty peritheca between them. The calices
are usually circular in outline, but in many specimens where
they seem to be more crowded together than in others they
become angular and distorted, but never regularly hexagonal.
The septa vary greatly in number, but in a typical calyx

CORALS

there are about twelve large septa alternating with twelve
smaller septa. The larger septa are usually slightly exsert,
and are continued over the lip of the theca into twelve
costae, which are extended on to the peritheca to meet the
costae of neighbouring calices.

In most examples there is a trabecular columella to
which the larger septa are joined, but this structure is
rudimentary in others.

If a large colony be carefully examined some calices
will be found more elongated than the rest and show a
constriction which indicates a division of the calices into
two equal or unequal portions. This may be taken as a
sign that the usual method of increase in the number of
polyps is by the process of splitting into two or by
fission.

The process of fission is brought about in these corals
by the increase in one diameter of the calyx accompanied
by an increase in the number of septa, and this is followed
by a constriction of the calyx wall in a plane at right
angles to the diameter which has increased in length
and the constriction is continued until the single calyx is
divided into two calices. The fission of the coral polyp is
on the same plan as that of the calyx, an increase in the
number of the mesenteries being followed by a vertical
plane of constriction of the body wall of the oral disc and of
the crown of tentacles ; and finally, the division of the
polyp vertically into two polyps.

This method of asexual reproduction of the individuals
of a colony of Favia is undoubtedly the most common, but
it is not the only one, because at the base or, in the encrust-
ing forms, at the growing outside edge of some specimens
small calices may be found arising from the coenosteum
between the other calices. Increase in numbers of in-
dividuals, therefore, may occur not only by fission but also
by gemmation in this genus.

In the anatomy of the polyps of Favia there is one point
of special interest to which attention should be drawn.
In the polyp of Galaxea, as alread\' mentioned, there are
two pairs of directive mesenteries as in most of the sea-

MADREPORARIAN CORALS 53

anemones and Madreporarian coral polyps, but in the
Astraeid coral polyps that divide by fission the directive
mesenteries are usually absent. Duerden, who first called
attention to this fact, considered that the absence of directive
mesenteries in the polyps of an Astraeid colony could be
taken as a sign that the method of reproduction was by
fission, and vice versa that the presence of the directive
mesenteries was a sign that the method of reproduction was
essentially one of gemmation. There are some exceptions,
apparently, to this interesting and important generalisation,
for in the genera Cladocora, Stephanocoenia, and Solena-
straea, which are apparently fissiparous, the directive
mesenteries occur, and in two species of Favia investigated
by Matthai the polyps that arise by gemmation do not
possess directive mesenteries.

GoxiASTRAEA. — In the genus Goniastraea (Fig. 18),
another widely distributed coral on the tropical reefs, the
calices are so crowded together that the thecal walls are
actually in contact, the common coenosteum being ap-
parently absent. As a result of this crowding the calices
have lost their round contour and become angular, but
they do not form a hexagonal pattern, some being triangu-
lar, some roughly quadrangular, and others pentagonal or
irregular.

Among the more irregular forms a few calices may
usually be found with a constriction in the middle which
shows that the usual method of reproduction is by fission.

In the characters of the septa and in some other respects
the genus Goniastraea is very similar to Favia.

We have seen that in Favia and Goniastraea some of
the calices become elongated and then constrict to form
two calices. In other genera the elongation takes place,
but the constriction is delayed so that the calices assume
the form of long straight or sinuous grooves, provided on
each side with rows of septa and separated by ridges from
similar grooves representing the neighbouring calices. The
extreme forms of this modification are seen in the group
of Astraeids commonly known as the Brain corals, from the
fact that these sinuous calices give the rounded surface of

CORALS

the coral an appearance similar to the convoluted surface
of the human brain.

Between the Brain corals and the Favia type of coral,
however, there are many intermediate forms which in a
series show an increasing number of elongated sinuous
calices among the round or angular ones.

DiCHOCOENiA. — An example of such an intermediate
stage is shown in the figure of a specimen of the genus
Dichocoenia (Fig. 19). In this genus some of the calices
seem to be circular in outhne, and, as they are in some

Fig. 19. — Dichocoenia pulchcrrima. A small specimen. Xat. size.

species separated by a scanty vesicular coenosteum, have
an appearance somewhat like that of Favia, though amongst
them there are many elongated straight or sinuous cahces
which show no trace of constriction. But these elongated
calices are relatively short as compared with the long
labyrinthine calices of a true Brain coral.

The septa of Dichocoenia are well developed, slightly
exsert, and, as in Favia, are continued over the lip of the
calyx wall as costae which meet the costae of neighbouring
calices on the peritheca.

The most familiar of the Brain corals are those included

MADREPORARIAN CORALS 55

in the genera Meandrina, Coeloria, and the closely related
genus Leptoria.

Meandrina. — In Meandrina the calices are principally
represented by long sinuous valleys, but in places more
circumscribed calices may be found. Between the valleys
there are ridges representing the fused walls of the calices,
for in these genera there is no peritheca as there is in Dicho-
coenia. There are numerous close-set septa and a median
spongy columella. The general appearance of the surface
of one of these Brain corals, as they are seen in a museum,
with all the soft fleshy parts removed, is that of a labyrinth
or maze of valleys without any regularity or order in their
arrangement ; and, if a single valley is traced for any
distance and found to divide into two valleys or to run into
another valley, it is difiicult to believe that they are essenti-
ally the same thing as, or, to use the scientific phrase,
morphologically homologous with, the calcareous cups that
support the well-defined polyps of such a coral as Galaxea.

The series of intermediate forms which have been de-
scribed suggests that it must be so ; but the evidence would
not be complete without some knowledge of the characters
of the animals that construct them.

In a living Brain coral the valleys are covered by a
continuous lamina of soft fleshy substance rising a few
millimetres above the hard coral substance, and this lamina
is perforated at intervals of 2 or 3 mm. by a number of
slit-like holes, the polyp mouths. The lamina rises on each
side to the ridge which is provided on both sides with two
rows of short stumpy tentacles.

The colour of the living expanded polyps of the Brain
corals is often very vivid and brilliant. The oral lamina is
bright green with the mouths outlined in brown. The
tentacles are sienna-brown, becoming paler as they are ex-
tended in full expansion in search of food. When the polyps
are contracted, however, the green colour is lost owing to
the tentacles folding over the lamina, and the whole coral
seems to be covered by a darkish brown slime. There is a
great deal of variation in the shades and tones of colour in
these as in other corals ; and it is interesting that the notes

CORALS

the author made of the colour of a Brain coral in North
Celebes are almost identical with the descriptions of the
colours of Mcaiidrina lahvrinthica by Duerden in Jamaica.

But to return to the anatomy of the polyps. Each of
the mouths that are found in the lamina leads into a short
throat (stomodaeum) which is suspended in the general
cavity h\ an attendant set of mesenteries. There is free

I-'iG. :;o. — Meandriua. Nat. size

communication between any one mouth and the cavity,
between the individual mesenteries of a set and the cavity
of the sets of mesenteries on each side of it. If, therefore,
we try to maintain that each mouth with its stomodaeum
and its set of mesenteries corresponds with a polyp, an
individual polyp, of such a coral as Galaxea or Favia, we are
met with the difficulty of determining, in the absence of a
limiting body wall, where one polyp ends and the others

MADREPORARIAN CORALS 57

begin, and also what number of tentacles of the ridges
legitimately belong to one polyp and what to the next. It
is diihcult to think of an individual which has no well-defined
limits. But the difficulties are no less if we try to maintain
that a whole valley with its ridges corresponds with the
single polyp of a Galaxea. It is quite conceivable that an
individual may have two or indeed any number of mouths,
or two or a reasonable number of sets of organs. But if we
study the anatomy of Meandrina carefully we find that one
valley communicates with the others as freely as one set of
organs communicates with another in a single valley, and
therefore our new proposition leads to the conclusion that
the whole set of mouth and organs represents only one
individual polyp. Which, it might be said, is absurd.
There is no solution to this problem unless there is a perfectly
clear conception in the mind of the WTiter or reader of the
meaning of the word " individual." The only reasonable
solution of the difficulty is, as suggested in Chapter I., to
abandon the use of the term Individual as applied to Polyps
in organic continuity and to regard the coral as a whole
as the only true " Individual."

EuPHYLLiA. — Another group of Astraeid corals is repre-
sented in most large collections by the genera Eusmilia,
Euphyllia (Eig. 21), and Mussa. From a thick stem attached
to a rock or to another coral the colony divides irregularly
into two or three stout branches, which may again subdivide.
Each terminal branch ends in a relatively large calyx, in a
typical form 20-30 mm. in diameter. The calices may be
round or oval or triangular, or more irregular in outline,
and they may show the constrictions which are evidence of
division by fission. The method of colony formation is
technically known as " caespitose," as it has a slight
resemblance to the method of branching of some turf
plants.

The septa are numerous and very variable in number,
according to the size of the calyx. There seem to be three
or more orders of septa. The septa of the first order are
large and almost reach the centre of the calyx, those of the
second order alternating with those of the first are smaller.

58 CORALS

wiiilc those of the third and subsequent orders are very
small, and only to be found in the upper part of the
calyx.

The differences between the three genera are not of very
great importance, and it may be that when some one has the
courage to revise the system on which the genera of these
corals is based thev will be amalgamated. In Eusmilia,

Fig. 21. — Euphyllia, East Indies. | nat. size. The line called the " Edge-zone "
can be distinctly seen about I inch l)elow the rim of each calyx.

according to the system in vogue, there is a spongy columella
at the bottom of a deep fossa, in Mussa it is rudmientary,
and in Euphyllia it is absent. Mussa differs from the other
two in having widely separated spines on the theca and
dentate septa, and also in having the septa very much more
exsert. Apart from the difference as regards the columella,
a very variable character on which to base a generic dis-
tinction, Eusmilia and Euphylha are almost identical. It
has been the custom, however, to refer specimens from the

MADREPORARIAN CORALS 59

West Indies to the genus Eusmilia and specimens from the
East Indies and Pacific to the genus Euphvlha.

The characters of the polyps in the three genera seem to
be very much ahke. In a Hving specimen there is an oral
disc surrounding the mouth, and at the margin of the calyx
there is a large number of short finger-shaped tentacles.
Outside the margin of the calyx the soft living substance
extends downwards for a few millimetres like a finger-stall
covering the hard corallum. This outer skin is called the
Edge-zone by Enghsh authors (in German " Randplatte ").
Below the Edge-zone the corallum is exposed, and is usually
subject to the attacks of boring worms and other destructive
agents, or is partly protected by Polytrema or Polyzoa or
other encrusting forms of animal and vegetable life.

The " Edge-zone " has another point of interest, as its
lower limit can be fixed in the coral after the removal of
the soft parts by the texture of the surface. Above the
limit the surface is compact and marked b}^ more or less
well-pronounced costal ridges ; below the limit the surface
is chalky in texture, and there is no trace of costal
ridges.

i\ccording to Bourne, " the Mussa of Diego Garcia is of
a dull brown colour, with olive-green disc and tentacles."
According to Ehrenberg, the polyps are pale brown with
a golden-yellow disc. Duerden describes the colours of
another genus — Isophyllia, closely related to Mussa — found
on the reefs of Jamaica as follows : " The prevailing colours
are dark green, brown, and yellow, with minute, opaque
white, superficial granules distributed practically all over.
The yellow colour predominates along the thecal ridges and
the green along the valleys. Irregular, opaque white, cream,
or green patches are sometimes present on the disk, ending
in streaks towards the periphery, that is, in the region
covered by the overfolding column wall."

The Astraeidae that have so far been described have the
more characteristic massive, spherical, or lobed form of the
members of this family. Some statement must now be
made concerning the corals that clearly belong to the family
but have a different appearance. They may be arranged in

CORALS

three categories, (i) the fohaceous Astraeids, (2) the dendritic
Astraeids, and (3) the sohtary Astraeids.

Merulina. — This coral (Fig. 22), found in the Indo-
Pacific Oceans, is one of the commonest of the foliaceous
Astraeids. Its general form is that of a huge cabbage-like
vegetable, attached by a thick stem, and sending off, more
or less horizontally, a few large leaves or fronds.

When the upper surface of one of these fronds is examined

it has the appearance of
a raised map of a moun-
tainous country, a com-
plex of hills and valleys
with a general inclina-
tion from the base to
the periphery of the
frond (Fig. 22). Here
and there on the surface
of the fronds there are
irregular raised patches,
which would correspond
with high mountain
peaks. When the slopes
of the valleys are ex-
amined more carefully
with a magnifying glass,
they are found to be
traversed by a series of
parallel laminae, which
can be recognised as
the septa of an Astraeid
coral. In some places
there may be found little round pits or oval depressions,
where the septa have a tendency to radiate as from a
common centre, but there are no other indications of any-
thing corresponding with discrete calices.

We have, in fact, in Merulina as in the Brain corals, a
complete continuity of the calyx units that are so well
defined in the more primitive compound Astraeids.

The general form and surface markings of Merulina might

Fig. 22. — Merulina. The upper surface of
a part of a frond. Nat. size.

MADREPORARIAN CORALS 6i

possibly lead to a confusion with another coral belonging to
a different family, namely, Pachyseris (Fig. 29, p. 75).

It is therefore important to note that the surfaces of
the septa are armed with a profusion of spines, but that
these spines never meet across the interseptal spaces to form
bars (synapticula), binding the septa together as they do
in the family to which Pachyseris belongs.

EcHiNOPORA. — Another foliaceous x\straeid, not in-
frequently found on the Indian and Pacific coral reefs, is
Echinopora. The thin lobes or laminae of this coral exhibit
a very different arrangement of the calices, as they are far
more clearly defined and separated from each other by con-
siderable intervals of coenosteum. In the centre of each
calyx there is a broad and conspicuous spongy columella,
and from this radiate a number of thick septa, continuous
over the lip of the calices with very well-marked costae,
spreading over the coenosteum and joining up with the
costae of neighbouring calices to form continuous ridges.
As the generic name implies, Echinopora is also characterised
by the rich endowment it possesses of sharp spines. The
septa are edged with rows of strong sharp teeth, which are
particularly well developed in the neighbourhood of the
columella, and the whole surface of the coenosteum is armed
with numerous spines.

Cladocora. — Of the recent dendritic Astraeids, the
most familiar is Cladocora. One species (C. arhnscula) of
this genus is found in the Mediterranean Sea, but it is more
characteristic of the warmer waters of the Atlantic Ocean.

" Small bush-like colonies of this species occur in numbers
in the shallow waters of Kingston Harbour in Jamaica and
at other points around the coast, either free or attached to
loose pebbles or shells. Larger colonies are found in water
of from three to six feet, and thickly incrust the bottoms of
boats phing in the harbours " (Duerden).^ The branches
of this dendritic coral terminate in small columnar calices
4-5 mm. in diameter.

Each calyx has a variable number of exsert septa,
several pali, a well-developed columella, and simple granular

^ Mem. Xat. Acad. Sci. Washington, vol. viii., 1902, p. 558.

62 CORALS

or spiny costae. The most usual method of asexual repro-
duction is by lateral columnar gemmation, but a process,
called fissiparous gemmation by Duerden, also, but rarely,
occurs.

The expanded polyps are light brown in ccjlour, and are
provided with twenty-four to thirty-six slightly knobbed
tentacles arranged in three or four cycles. The margin of
the disc has sometimes a bright iridescent colour. As with
nearly all the gemmiparous Astraeids, the polj'ps of Clado-
cora are provided with two pairs of directive mesenteries.

The genera of Astraeidae that do not form colonies
{Astraeidae simplices) are among the rarities of museum
collections, and our knowledge of their anatomy is very
imperfect.

The essential difference between a simple Turbinoliid
coral and a simple Astraeid is that in the latter the base of
the cup is more or less blocked by endotheca.

But some of them differ from the ordinary Turbinoliids,
and resemble some of the Astraeids in having the septa
armed with numerous spines. Any differences which may
exist in the structure of the polyps have yet to be discovered,
and it may possibly be proved that the separation of the
two groups is unnatural. The solitary Astraeids do not
seem to be abundant anywhere in modern times ; a solitary
specimen here or a half-dozen specimens there is the onl\-
booty of the fortunate collector. In no locality, so far dis-
covered, are they found in great numbers. They are not
confined to any one region, but may be found in deep or
in shallow water in the warmer seas of the world.

t^AMILY 4. FUXGIIDAE

The characteristic feature of this familv is that the
septa are united by synapticula. The synapticula are bars
of solid coral substance that pass horizontally from one
septum to another and in doing so perforate the mesenteries.
In some respects the Fungiidae are intermediate between
the imperforate corals previously described and the perforate
corals, for, although the septa and the theca are usuallv

MADREPORARIAN CORALS 63

imperforate, there are some forms in which either septa or
theca or both are porous. It is quite clear that any attempt
to divide this family into two groups on the character of the
perforation or imperforation of the corallum would be un-
natural and unsound.

The genus Fungia (Fig. 2^) is a solitary coral and can
readily be distinguished from the solitary corals of other
families of Madreporaria, but nearly ah the other genera are
compound or colonial corals, the corallum being built up by
the activities of a large number of polyps, and many of these
seem to approach very closely in structure to corals belonging
to other families. It is in such cases that the determination
of the presence or absence of synapticula becomes a matter
of great importance.

According to the system adopted by Duncan and sub-
sequent authors, the group of corals which is here called
Fungiidae constitutes a separate section of the Madreporaria
called the Madreporaria fungida, and this section is divided
into a number of families. Of these families the one called
Fungiidae includes the genera Fungia, Halomitra, Herpeto-
litha, etc., the family Plesiofungiidae includes the important
genus Siderastraea, and the Lophoseridae includes the genera
Agaricia, Pach^-seris, Pavona, etc. The Plesiofungiidae are
in some respects a transition group between the Fungiidae
and the Astraeidae, and an extinct family, Plesioporitidae,
forms a transition group between the Fungiidae and the
Madreporidae.

Fungia. — The best known and most widely distributed
of the genera of the Fungiidae is the " Mushroom coral,"
Fungia. On many of the tropical coral reefs of the old
world it can be collected in cart-loads, and attracts attention
not only on account of its size — for it may be a foot in
diameter — but on account ot its curious resemblance to the
inverted disc of a mushroom. Moreover, it differs from the
other corals of the reef in being free, in the adult condition,
so that it can be lifted and examined without forcibly
detaching it from any basal support.

The history of our knowledge of Fungia presents^^me
features of special interest to which reference rm

64 CORALS

The early belief that the Fungia was simply a mushroom
which had, in some mysterious wa}', fallen into the sea and
been turned into stone was finally disposed of by Rumphius
in 1684, who proved conclusively that the structure of
Fungia is totally different from that of a Fungus.

But Rumphius did more than that, for he gave, for the
hrst time, an account of the coral polyp. He said that
when the coral is seen alive in the water it is covered with
an animal-like (" diergelyke ") mucus, that it is provided with
innumerable oval tentacles ("langwerpigeblaasjes"), and that
when it is taken out of the water this mucus and the tentacles
contract between the septa. Although he compared the
mucous substance of the Fungia with that of a jelly-fish
(" zeequalle "), he was not sufficiently in advance of his time
to declare boldly that it was an animal and thereby anticipate
the discovery by Peyssonel and Ellis, a century later, of the
animal nature of corals, but was contented with the some-
what vague conception that it is intermediate between a
stone and a zoophyte.

One of the most interesting facts that have been dis-
covered about Fungia is that the familiar large unattached
specimens are preceded in development by a stage in which
they are attached by a short stalk to a rock.

The first reasonably clear and illustrated account of this
stage was given by Stutchbury in 1830, but it was not until
quite recent times that a complete description of the way
in which the Fungia is formed from the attached stalk and
is subsequently detached from it has been given by Bourne.^
It is interesting, however, to find that the stalked form did
not escape the notice of Rumphius,- who says that " some-
times a little foot can be seen on the underside by which
it is attached, but not firmly, to the rocks."

In a large collection of specimens of Fungia there can
usually be found at least one which is almost completely
circular in outline, and it is convenient to use such a form
for a first study of the structure of the genus. Variations
of this type can be studied later.

1 G. C. Bourne, Trans. Roy. Dublin Soc. v., 1893.
- Rumphius, Amboinsch Kruidboek, vol. vi. Book xii. p. 247.

Fig. 23. — Fungia. The septa in some places in this specimen are rather water-worn,
exposing the synapticula more clearl}- than in perfect specimens. Nat. size.

MADREPORARIAN CORALS 65

The upper surface of a Fungia of this type is slightly
convex and frequently raised into a shallow mound towards
the centre. The under surface is slightly concave, so that
the coral rests on its margin when placed on a liat table.
The upper surface is provided with a very large number of
vertical radially disposed laminae — the septa — with sharp
dentate or sinuous edges. The under surface is marked by
a corresponding series of shallow radial ridges — the costae —
armed with rows of blunt tubercles. Between the ridges on
the under side there is solid coral substance representing
the theca of the cup corals. In the centre of the under
surface there may be an ill-defined circular area, better
recognised in small than in large specimens, somewhat raised
or depressed and free from costal ridges. This will be
referred to as the " scar."

In the centre of the upper surface there is a deep groove
or fossa from which the septa radiate to the margin of the
coral. This fossa may be taken as an indication that the
coral does not exhibit perfect radial symmetry but may be
divided into two laterally symmetrical halves along a
diameter, which may be called the directive diameter and
is parallel with the median line of the fossa.

The septa are so numerous and close set that there is
difficulty in counting them and reducing them to a system ;
but in a good specimen a large septum can be seen passing
from each end of the fossa to the periphery in the same
plane as the directive diameter. These are the directive
septa. And on each side of the plane there are five other
large septa which pass from the side of the fossa to the
margin.

These ten septa together with the two directive septa
constitute the primary twelve septa of the coral and were
the earliest septa to be formed in the development of the
coral. The other septa have been formed later and inter-
posed between the primaries in series, and thus we have
secondaries, tertiaries, and quaternaries, etc., each series of
septa being smaller than the preceding series and approaching
less closely to the fossa. The determination of the series
of septa in any specimen of good size requires the exercise

66 CORALS

of a great deal of care and patience, and many difficulties
have usually to be overcome owing to irregularities in growth.

It cannot be expected that any one would care to deter-
mine the orders of sequence of the septa unless he were
specially interested in the group, but it is of importance for
the student of corals to understand that the general prin-
ciples of septal sequence are manifest in Fungia with its
hundreds of septa, as in other Madreporarian corals with
septa that can be more easily recognised and counted.

The most important point to notice in the study of the
septa of this coral, however, is the presence of the svnapticula.
It is important because the synapticula form one of the
characteristic features of the family and because in Fungia
they are larger and more easily studied than in any other
genus. The synapticula are bars of coral substance that
pass from one septum to another at regular intervals, binding
the septa together and giving rigidity and strength to the
coral as a whole. As a rule the synapticula do not appear
near the upper regions of the septa but are more or less
hidden in the depths of the interseptal spaces. They can
usualty be seen, if the specimen is not too massive, by holding
the coral in front of a strong light, or, for more careful study,
by filing down the septa of a part of a spare specimen until
they are reached.

It may be an open question whether in Fungia there is
a true columella. The fossa is usually deep and at the
bottom of it there is a plexus of calcareous trabeculae which
may be regarded as a rudimentary columella.

The single large polyp that gives rise to this coral has a
slit-shaped mouth in the centre of the disc above the fossa,
and it is surrounded by an enormous number of long tentacles
slightly inflated at the extremity. It might seem at first
sight that the tentacles are indefinite in number and irregu-
larly scattered over the surface of the disc, but a careful
study of the hard and soft parts has shown that each tentacle
is situated on a slight elevation close to the innermost edge
of a septum and that consequently the tentacles have the
same orderly sequence as the septa and are arranged in
regular cycles. The soft fleshy body wall of the polyp covers

MADREPORARIAN CORALS 67

the whole of the under surface of the coral, in a healthy
specimen.

The mouth leads into a short stomodaeum or throat, and
between the throat and the body wall there are as many
mesenteries as there are septa. The pair of mesenteries
situated at the angles of the mouth, one mesentery on each
side of the directive septa, are the directive mesenteries.
The other mesenteries are situated between the lateral septa
and are either complete or incomplete, the primary and
secondary mesenteries extending the whole distance from
the margin to the throat, the others extending only a part
of the distance from the margin to the throat, according to
the series to which they belong. In the lower parts of the
disc the mesenteries are perforated by the synapticula.

It will be seen from the account given above that the
polyp of a Fungia is an ordinary Madreporarian polyp and
presents no feature of an extraordinary kind except its great
size and the perforation of the mesenteries by the synapticula.

The colour of the polyps is very variable, some specimens
being described as green and others as brown, but the inflated
tips of the tentacles are white.

No account of the structure of Fungia would be satis-
factory without reference to some of the principal variations
from the types that have been described.

On some reefs the symmetrically round disc shape is
rare, most of the specimens being elongated in the directive
diameter so as to become, oval. Other variations may be
found in which the fossa is not elongated but an almost
circular pit, or the upper surface very convex or the outline
quite irregular. In some specimens the thecal wall as seen
between the costae is perforated.^

Variations in colour have already been referred to, but
there seems to be also some difference between species or
perhaps simple variations in the length of the tentacles.
Rumphius refers to them as little blisters (" blaasjes "), and
Dana says the tentacles are small and rudimentary, but the
excellent photographs of the living polyp by Saville Kent,

1 specimens showing an imperforate thecal wall were formerly placed
in a separate genus Cycloseris.

68 CORALS

and the observations and drawings of other authors, prove
that in some cases, at least, the tentacles are of consider-
able length, like those of the common British sea-anemone
Tealia.

It has been said that Fimgia is free, and so it is in the
adult condition when it is large and conspicuous ; but in
the early stages of its development it is fixed by a base of
attachment to a rock or to another coral. In the young
fixed stage Fungia is very much like a Caryophyllia. It

Fig. 24. — Young stalked form of Fungia. R., a part of the rock to which it
is attached. S., the stalk showing the line when fracture ii about to take place.
Nat. size.

has an irregular base of attachment, an imperforate thecal
wall, and twelve primary septa. This stage is called the
Trophozooid. After a time the free edge of the Trophozooid
expands and, becoming wider and wider, gives rise to a second
stage with a form like the mouth of a trumpet. When the
expanded part of the coral, the Anthocyathus, at this stage
has reached a certain size — the septa having increased in
number as it has grown — it breaks off and becomes the
free Fungia (Fig. 24). The stalk or basal part, called the
Anthocaulus, remains behind and gives rise to another

MADREPORARIAN CORALS 69

Fungia in the same way or, by lateral budding, may give
rise to several young Fungias.

This very remarkable and unique method of reproduc-
tion is of very great interest because the detachment of the
Anthocyathus from the Trophozooid seems to be a method
of reproduction by fission quite unlike the fission seen in
other corals. It is not vertical, but horizontal or transverse
fission. It is different also from ordinary fission in the
respect that the products are unequal and unlike each other.
The lateral buds that are formed on the Anthocaulus after
the Anthocyathus has broken off seem to be formed by
gemmation in the ordinary way ; so that in Fungia we
have reproduction by gemmation as well as by this
extraordinary method of fission. It is probable that
gemmation also occurs in the free adult stages, because,
when the under sides of a number of large Fungias are
examined, a few young forms are occasionally found at-
tached to the thecal walls. This was observed by Ellis,
who wrote, " In many curious collections, such as those
of the Duchess Dowager of Portland and of Dr. Fothergill,
there are many young ones (of Madrepora fungites) ad-
hering to the old ones with large rising lamellae as in
the old ones." ^ The development of these young ones
has recenth' been described by Boschma, who has proved
that they are produced by gemmation and not from free
larvae. 2

But that is not the whole story, for in some species,
formerly placed in a separate genus Diaseris, the disc-
shaped free coral, when it has reached a certain size, divides
by vertical fission into four quadrants, and each survives to
restore in the course of time by unequal growth the three
missing quadrants of its body.

Fungia has been shown to be a solitary coral, but its
corallum has a very similar appearance to the coralla of a
series of genera which are really compound corals.

Halomitra. — The first of this series is the genus Halo-
mitra, originally described by Rumphius under the name

^ Ellis, Zoophytes, p. 153.
^.H. Boschma, Proc. koning'i. Akai. Wet. Amstevdam, xxvi., 1923.

70 CORALS

Mitva polonica, or Polish cap, on account of its cup or cap
shape.

Although many variations in its exact form are now-
known, the most characteristic specimens are deeply concave
on the under surface, the area round the central fossa being
raised on the top of the convex upper surface. The numerous
septa passing radially from the fossa to the circumference
of the coral are not all straight and continuous, as the\' are
in Fungia, but some of them appear to be deeply indented
in their course, forming pit-like depressions to which neigh-
bouring septa are inclined and from which new septa arise.

These pits represent the position of a series of small
secondary polyps arranged more or less irregularly in a ring
or series of rings round the central polyp of the fossa.

Herpetolitha 1 is the next genus in this series, and can
usually be distinguished from the other genera by its elon-
gated form, which is sometimes bent in a serpentine fashion
(Fig. 25). Running along the middle of the upper surface
is a long deep fossular groove in which the septa appear
to radiate not from one centre but from a number of distinct
centres, and the septa on each side of the groove are inter-
rupted in the same manner as they are in Halomitra by a
large number of irregularly scattered pits.

In a figure of a living Herpetolitha given many years
ago by Dana it is shown that in the flesh that covers the
median groove there is a series of mouths, each one sur-
rounded by a patch of bright green colour in marked contrast
to the brown colour of the tentacles and other parts of the
coral polyp, and similarly that in each of the lateral pits
there is a little mouth surrounded by a green patch and a
circle of browm tentacles. We have in Herpetolitha, there-
fore, an advance on the structure of Halomitra in that the
corallum is constructed by a number of larger polyps in the
median fossa and a greater number of smaller polyps
situated laterally.

Specimens of this genus sometimes reach a very con-
siderable size. There is a specimen in the Manchester
Museum 13 inches in length and 3^ inches in width, which

1 Frequently spelt Herpolitha by authors.

Fig. 25. — Herpetolitha, showing the elongated fossa and the cavities at the sides
which arc occupied by small polyps. | nat. size.

MADREPORx\RIAN CORALS 71

weighs a little over 2 lb., and no doubt larger specimens
than this have been found.

The development of Herpetolitha has not yet been fully
worked out, but the presence of a distinct scar on the under
side of small specimens leaves no doubt that in the early
stages it is provided with a stalk of attachment as in Fungia.

PoLYPHYLLiA. — The final stage in this series of genera
is found in Polyphyllia, in which the sharp distinction
between calices of the median groove and the lateral calices
tends to become lost, and the corallum seems to be composed

Fig. 26. — Siderastraea radians. West Indius. A small specimen. Xat. size.

of a number of very irregular and incomplete calices of
various sizes.

All these genera, except Fungia, are confined to shallow
water of the tropical Indo-Pacific regions.

The genera of the family which have been described
above are all free in the adult stage, those that are still
to be considered are permanently attached to some other
coral or rock.

SiDERASTRAEA. — The gcuus Siderastraca (Fig. 26) in-
cludes a number of corals which are very abundant on the
West Indian reefs and occur also in the Indian Ocean and

72 CORALS

elsewhere in tropical seas. In habit they resemble some
of the more typical Astraeid corals, being massive, dome-
shaped, lobate, or encrusting, and the surface is honeycombed
with small close-set calices without any intervening coeno-
steum. There can be no doubt that the old generic name,
Astraea or Star-coral, was hrst given to a member of this
genus, and it seems an unhappy fate for it to be removed to
another family than that to which it gave the family name.
A detailed examination of the structure of the coral,
however, proves quite conclusively that it is more closeh'
related to Fungiidae than to the Astraeidae, but it differs
from the Fungiidae sufficiently to justify the course, which
many authors prefer, of placing it, together with a large
number of extinct genera, in a separate family or sub-
family called the Plesio-fungiidae.

The calices are usually quite small {i.e. 4-6 mm. in
diameter), and each calyx is separated from its neighbours
by a common thecal wall which is rounded above and ridged
by the outer edges of the septa. The septa are numerous
(36-48) and arranged in several series of magnitude, as in
Fungia, but it is a characteristic feature that thev are,
relatively to the size of the calyx, very thick, so that the
interseptal spaces are very narrow. The free edges and
the sides of the septa are beset with many coarse granular
tubercles, and in the lower parts of the septa some of the
tubercles of adjacent septa meet to form true synapticula
(Fig. 27).

It is perhaps of some importance to note that in Sider-
astraea neither the septa nor the thecal walls are ever
perforated by holes, so that it is strictly an imperforate
coral. The calyx is considerably depressed in the middle,
and from the bottom of the central pit there rises a short
papillose or smooth but perfectly distinct columella.

The method of asexual reproduction is very difficult to
understand b}' the study of the dried corallum. Small
young calices can be seen interposed in the angles between
the older ones and appear to arise from the common thecal
wall. In some cases it might be supposed that the young
calyx has arisen from an older one by a process of fission,

MADREPORARIAN CORALS

but the researches of Duerden have shown that the process
is only a special form of gemmation which he calls " fissi-
parous gemmation."

The appearance of a living colony of a West Indian
Siderastraea has also been fully described by Duerden. ^
According to this author the small expanded polyps (5-6 mm.
in diameter) are outlined by a narrow polygonal groove of
a hghter colour than the rest of the polyp wall. This
groove corresponds with the upper limit of the common
calicinal wall between the polyps. The expanded polyps

'■-^^■* '^

Fig. 27. — Siderastraea siderea. A small portion of the surface of a specimen
from the West Indies, showing the calices, septa, and synapticula. x 6 diams.

rarely assume a cylindrical form with a ifattened terminal
disc, like most coral polyps, but exhibit merely a dome-
like elevation of the walls over the calyx (2 or 3 mm. high).
In contraction they are not covered over by a fold of the
body wall, but, as in Fungia, the tissues and the tentacles
sink down as far as possible into the spaces between the
septa. The tentacles are wide apart and occupy a broad
band round the oral disc. When fully expanded they
consist of a broad basal part which, in most members of the

^ J. E. Duerden, " The Coral Siderastraea," Carnegie Publications oj
Washington, 1904.

74 CORALS

inner cycles, becomes bifurcated, each brancli terminating
in a knob armed with batteries of nematocysts ; the other
tentacles are simply digitate. The colour of the polyps
varies according to the position of the colony on the reefs.
If they are not exposed to the sun they may be colourless,
but elsewhere they vary from light to dark brown. The
oral disc may show radial streaks of velvety green and the
angles of the mouth and the knobs of the tentacles are white.

The following genera belong to the section of the family
sometimes called the Lophoseridae.

Agaricia. — This coral forms colonies which are usually
foliaceous in growth, the calices arranged in irregular con-
centric rows on the upper or, more rarely, on both sides of
the leaves (Fig. 28). The rows of calices are separated by
prominent thecal ridges. The calices are small, 3-4 mm.
in diameter. The septa are numerous, as in other Fungiidae,
but do not extend from the margin as close to the centre
of the calyx as they do in Siderastraea, and consequently
leave a deeper and wider oral pit. The sides and margins
of the septa are profusely tuberculate, and in the depths of
the interseptal spaces the tubercles meet to form synapti-
cula. Asexual reproduction is by fission.

Agaricia seems to be a widespread but not very common
coral on both East and West Indian coral reefs. In Jamaica,
according to Duerden, the colonies occur in shady places
at a depth of from 3 to 4 feet downwards, and are of a con-
spicuous bright reddish-brown colour. The tentacles are
rudimentary, from ten to eighteen in number, and widely
separated. In the state of contraction this coral resembles
other members of the family in that the polyp walls are
not folded over the oral disc. In the state of expansion,
emerald green circles can be seen surrounding the mouth
on the oral disc.

As in many other corals in which asexual reproduction
is by fission, there are no directive mesenteries in the polyps.

Pavona. — The genus Pavona, which belongs to the same
group as Agaricia, does not occur in the West Indies but
is fairly common on some of the Indian Ocean and Pacific
reefs. It differs from Agaricia in having much less prominent

MADREPORARIAN CORALS 75

ridges, so that the surface is relatively smooth and striated
instead of being rough and ridged.

Pachyseris. — The last of these genera that need be
mentioned here is Pachyseris, which shows the most extreme
form of modification of the original system of distinct
calices (Fig. 29).

The coral is in the form of large rather thin cordate or
more irregular fronds attached by a short thick stem. The
under surface is a thin imperforate plate. The upper surface
consists of a series of concentric parallel ridges and valleys,
the valleys being traversed by an immense number of rela-

FiG. 29. — Pachyseris. A part of a large frond showing the cahces completely
merged into parallel ridges and grooves, x 2 diams.

tively thick and parallel septa. There is no indication
whatever of any distribution of these septa into discrete
calical areas. Pachyseris is a widely distributed but not
very common coral found in shallow water in the tropical
Indian and Pacific Oceans.

Family 5. Eupsammiidae

This family can readily be distinguished from the pre-
ceding families by the complete perforation of the walls
of the calices and, in most genera, of the septa as well. It
was formerly placed in the old division of Madreporaria
known as the Perforata, but in the general structure of both

76 CORALS

the coralluin and the polyps it is more nearly related to the
Imperforata.

In all the genera there are more than twelve septa, as
in most of the Imperforata, and a special character of the
fnmilv is that some of the septa fuse along their inner margins
to form a number of triangular interseptal spaces. In
most of the genera the septa and thecal walls are armed
with spines or small tubercles, but only in rare cases do they
join to form synapticula. The family includes both simple
and colonial forms.

Balanophyllia. — The little coral called by Gosse ^ " the
scarlet and gold star coral " [Balanophyllia regia) is a
representative of the solitary Eupsammiidae that is found
in British seas. It was found by that author attached to
the rock-pools at low-tide near Ilfracombe, associated with
the Devonshire cup coral [Caryophyllia smithii, Fig. 2, p.
26). It has since been found in other localities off the coasts
of Devonshire and Cornwall, but it is still far from being
one of the common objects of the seashore.

The dried corallum (6-8 mm. in height and diameter)
can readily be distinguished from that of Caryophyllia by
the two Eupsammiid characters — the perforation of the
walls and septa and the confluence of some of the septa
to form triangular interseptal spaces with their bases on
the thecal wall. The polyp is like a little sea-anemone
with a mouth situated on a cone rising from the centre of
the oral disc, and the margin of the disc is provided with
a single cvcle of about fifty long tentacles. Gosse described
the tentacles as " conical, obtusely pointed, without terminal
knobs," and there is little doubt that this is a good descrip-
tion of what he saw in the rock-pools at low tide. But de
Lacaze-Duthiers, who studied this species, from the coast
of France, alive in a small aquarium, says that when fully
expanded the tentacles are long and finger-like, and temiinate
in little knobs as in Caryoph3dlia. As in the latter coral
also, the sides of the tentacles are armed with batteries of
nematocysts which have the appearance of little warts.

The colours of the Devonshire specimens were described

' P. H. Gosse, British Sea Anemones and Corals, iS6o, p. 343.

MADREPORARIAN CORALS

Fig. 30. —
marginal bud.
Xat. size.

Endopachys grayi with a
Persian Gulf, 55 fathoms.

by Gosse as vivid scarlet in the adults, orange in the young

individuals, opaque ; the tentacles gamboge yellow, the

hue residing only in the

warts.

Endopachys. — The

genus Endopachys (Fig.

30) is still a rarity in

museums, and has not

been found in any locality

in large numbers. It is of

some special interest, how-
ever, because in size and

in form it closely resembles

the Turbinoliid coral

Flabellum, and, like

Flabellum, it is attached

to a stone or shell when

it is young, but becomes

free by fracture of the base in the later stages of its growth.

A critical examination of a specimen, however, shows that

it is thoroughly perforate
and that the septa have an
Eupsammiid arrangement
(Fig. 31). One or two
specimens only have been
found in such distant
localities as the Persian
(lulf, Hawaii, the Malay
Archipelago, and Manilla,
but the genus is repre-
sented by several species,
and is very abundant in
some of the Eocene de-
posits of the United States
of America.

Endopachys and Fla-
bellum present us with an excellent example of the

principle known as " convergence in nature." There can

be no doubt that they are not closely related, and

Fig. 31. — Diagram to illustrate the
septal arrangement of Endopachys. 1,1,
primary septa ; II, 11, secondary septa.

78 CORALS

we are justified in placing them in separate families,
but in order to become adapted to the same or similar
mode of life they have adopted the same external form and
a similar change in habit at the same time of life.

Both genera are usually found on a gravelly or sandy
bottom, in contrast to most corals, which are found on a hard
bottom. When they are very small they can be supported
on a small shell or stone, but when they are larger and
heavier than the stone there is a tendency for them to be
overbalanced and smothered in the gravel. The only way
to overcome this danger is to become detached from the
stone and support themselves as best they can as free
corals. We have unfortunately no record of observation
made on the hving coral, and it is not possible to hazard
a guess as to how this is done, but there can be little doubt
that the peculiar compressed cone shape and the variable
wing-like side processes in both genera are special adapta-
tions for this purpose.

Another point of interest about Endopachys is that it is
probably one of the corals on the verge of extinction. It
may have been very abundant in Eocene and later times,
and thus have become spread over a wide area in suitable
localities, but is now very rare, and shows the common
attribute of many rare things, a wide but discontinuous
geographical distribution.

Heteropsammia. — Another example of convergence,
but convergence of a different kind, is seen in the Eupsammiid
coral Heteropsammia (Fig. ^2). This coral is either solitary
or forms small colonies of two or three polyps by fission,
but it is very frequently free and associated in its freedom
with a small sipunculid worm like the Turbinoliid coral
Heterocyathus.

Both these corals are found on sandy bottoms, sometimes
in the Indian Ocean, together or in close proximity, and
they have found out quite independently the same dodge
for maintaining an upright position in the shifting sand.

Dendrophyllia. — I), ramea is a large branching coral
with a general form not unlike that of Lophohelia. And just
as the perforate solitary Balanophyllia is sometimes found

MADREPORARIAN CORALS

associated with the imperforate Caryophylha, so the com-
pound Dendrophyllia is found associated with Lophoheha.

Dendrophylha has a very wide distribution. The most
famihar species, D. ramea, is found in moderately deep
water in the Mediterranean Sea and in the Atlantic Ocean,
and other species occur in shallow water on the reefs of the
tropical Indian and Pacific Oceans. D. ramea sometimes
attains to an enormous size. De Lacaze-Duthiers records
the capture, by the fishermen of La Calle in Algeria, of a
block of this coral a cubic metre in size. It also shows a
complex amalgamation of branches similar to that described
and figured for Lophohelia proUfera (see Fig. 5, p. 28).

A critical examination
of the method of growth
of Dendrophyllia shows
that it is essentially
different from that of
Lophohelia. The great
branches of Dendrophyllia
are in reality enormous
calices with very thick
walls, on which the smaller
branches and calices have
arisen by lateral or thecal
gemmation. The calices
vary a great deal in size,

as in all these corals, but in a typical medium-sized specimen
in the Manchester Museum they are about 10-15 mm. in
diameter. Each calyx shows a deep and wide cavity, at
the bottom of which a more or less well-developed columella
may be seen. The septa are thin, barely exsert, not very
wide, and those of the young cycles bend towards and fuse
with the older septa as in other Eupsammiids.

The only account we possess of the polyps of a European
species of Dendrophyllia is that of D. cornigera, from the Golfe
du Lion, by de Lacaze-Duthiers, who says that the colour is
of a beautiful yellow-gold, the mouth being surrounded bv
a band of orange-red colour. The tentacles are very long
and of equal size and are dotted with little yellow spots.

Fig. 3^. — Heteropsammia. Indian Ocean,
30 fathoms. Upper surface on the right,
showing the calyx. Under surface on the
left, showing the aperture formed by the
sipunculid worm. Nat. size.

CORALS

In his description of the species Dcndroplivllin Willeyi,
on the reefs of the Cocos Islands, Dr. Wood-Jones says that
" when the colony consists of one or two polyps it is coloured
bright chrome yellow, w'hen older it is bright vermilion,
but at all times it has an iridescence resembling solutions
of eosin."

AsTROiDES. — Another Eupsammiid coral that has become
familiar to us is the Astroides calicidaris of the Mediterranean
Sea (Fig. ^^). This is the coral to which Boccone gave the
poetic name " la pierre etoilee." It usually forms small

encrusting colonies composed
of a number of calices about
7-8 mm. in diameter and 4 mm.
in height separated from one
another by a sparse coeno-
steum . The cavity of the calyx
is wide and deep, and rising
from the centre there is a well-
developed conical trabecular
columella. The septa of a
full - grown calyx are forty-
eight in number and arranged
in four cycles. There is less
regular and complete conflu-
ence of the third and fourth cycles of septa in Astroides
than is usual in the genera of this familv, but some con-
fluence does occur in nearly all the calices.

The polyps have a bright orange colour, and when fulh-
expanded stand up from the calices as tall columns termin-
ating in an oral disc surrounded by a crown of forty-eight
simple digitate tentacles.

This coral is of special interest to students of coral
morphology, as it was the subject of the important re-
searches of de Lacaze-Duthiers and von Koch which laid
the foundations of our knowledge of the embryology and the
development of the skeletal structures in the Madrepora.ria.

I'"iG. 33. — Astroides calicidaris. Medi-
terranean Sea. J nat. size.

CHAPTER IV

MADREPORARIAN CORALS (cOJttiuilcd)

" Die Corallenthiere sind nicht bloss fiir Naturbeschreibung und
Naturgeschichte im engeren Sinne merkwiirdig, sie gehoren zu den
zahlreichsten, auffallendsten, unbekanntesten und am einfluss-
reichsten Formen des organischen Lebens " — H. Ehrenberg, Abh.
Akad. Wiss., Berlin, 1834.

Family 6. Serl\toporidae

This family contains only three recent genera — Seriatopora,
Pocillopora, and Stylophora. They are found, commonly
but not abundantly, on most of the coral reefs of the world
except those of the West Indies. The family is of consider-
able interest from many points of view, and it is also
well defined and easily recognised. There has been a great
deal of difficulty in placing it in its proper position among
the families of the Madreporarian corals, as in some respects
it seems to have affinities with the old group of imperforate
corals, in other respects with perforate corals, and again in
the presence of very definite tabulae it agrees with some of
the extinct corals.

As the most striking feature of the anatomy of the two
genera is the definite restriction of the number of mesenteries
and of septa, in the full-grown zooid, to twelve, a feature
in which the family differs from all those that have been
previously described, and agrees with the Madreporidae
and Poritidae, the affinities are probably closer with the
perforate corals than with the imperforate.

Seriatopora and Pocillopora have the following char-
acters in common. They are colonial corals, forming pro-
fusely ramified shrubby or bushy growths reaching a size

81 G

CORALS

of a foot or two in diameter. The surface of the branches
is rough owing to the presence of a number of minute spines
or tubercles on the surface, and the calices are very small,
their appearance being represented by holes or pits usually
flush with the surface. There is of course some variation
in the size of the calices, but it may be found that in a large
collection of specimens the average diameter of the calices
at the margin is less than i mm.

These characters can be easily determined, but there are
some very important ones which require careful observation

and manipulation of the light
to be clearly demonstrated.

In many dried specimens
there seem to be no septa at
all even when the calices are
examined with a magnifying
glass. This may be due either
to the presence of the dried
remains of the polyp tissues,
which obscures the septa, or to
the calyx examined being old
and water-worn with the septa
partly destroyed. To examine
the septa, smaller terminal
branches should be thoroughly
cleaned by boiling in 5 per
cent, potash for some time and
then dried and examined in a good light, on a black ground,
with a pow'erful lens or low'-power microscope. It is only by
such means that it can be definitely ascertained that there
are nearly always twelve small septa, of which six may be
complete and six incomplete. Moreover, of the six complete
septa two are larger than the others and form a pronounced
ridge on the floor of the cup. These two septa are the
directive septa and they always lie in a plain parallel with
the axis of the branch.

The next two points to determine require the examina-
tion of a transverse section of a thick branch or the exposed
surface of a freshly made fracture. It may then be seen

Fig. 34. — Seriatopora. A few
terminal branches of a large colony.
Nat. size.

MADREPORARIAN CORALS 83

that each calyx is shut off b}' a thin tabula from a little
chamber below it, and this again by another thin tabula
from another chamber of the same diameter, or, to put
the same thing in another way, the corallum is perforated
by a number of radial tubes which are divided by thin
plates of coral substance into a series of closed chambers, of
which the outermost one is freely open to the surface and
forms the calvx. The Seriatoporidae are in fact Tabulate
corals.

Further, the same sections or fractures will show
that apart from these chambers the corallum is quite
solid and there are no communications between one set
of chambers and another. They are in fact imperforate
corals.

Our knowledge of the characters of the polyps is based on
the study of only a few specimens, but there seems to be
no doubt that as a rule the polyps are provided with twelve
short tentacles and twelve mesenteries, of which two pairs
are directive mesenteries. The tentacles of a species of
Seriatopora described by Fowler are capitate in form and
show the very remarkable and, in Madreporaria, unique
character of being introverted during retraction.

The polyps are connected with one another by a thin and
entirely superficial layer of coenosarc supported by the spines
of the coenosteum, and in this runs a delicate network of
nutritive canals. This elaborate system of canals, running
entirely superficially to the coenosteum, is similar to the
system of canals which connect the polyps in some of the
perforate corals, such as Madrepora and Dendrophyllia, but
in the case of the latter is continued downwards into the
perforations which traverse the coenosteum.

In the description of corals, pathological conditions are
not usually mentioned, and considerations of time and space
often render such a course imperative. But in this family
there is one kind of pathological change which is of excep-
tional interest. Like other corals, Pocillopora and Seriato-
pora may be attacked by certain barnacles, worms, and
mxolluscs in such a way as to modify in some way the normal
method of growth, but they are also liable to what may be

CORALS

prisoned for life (Fig. 35)

called a friendh' association with a little crab (Hapalocar-
cinus) .

^^'llen this crab is very small it settles down in the fork
between two young branches and, by some kind of continuous
irritation or stimulation, causes each branch to divide into
a number of lateral but anastomosing branch lets which,
spreading out on each side of the fork like a fan, eventually
converge above and form a cage in which the crab is im-

In some specimens a large num-
ber of these crab cages may be
seen, and so far as can be judged
by appearances they do not seem
to interfere with the general well-
being of the colony as a whole.
It may seem to be a bold asser-
tion to make, that imprisonment
for life is beneficial to any li\'ing
creature, but as the adult female
Hapalocarcinus is never found
anywhere except in one of these
cages it may be presumed that,
if she has a mind, she prefers it.
At any rate it is certain that
confined to this prison she can
obtain sufficient food for her
nourishment and can successfully
reproduce her kind.

The special point of interest
for the student of corals to consider is why these crab cages
are so frequently found in these two genera, Pocillopora
and Seriatopora, and not in others. The only recorded
instance of a crab cage of this kind on a coral of another
genus is in a specimen of Millepora from the West Indies,
now in the Public Museum at Liverpool, but they are not
known to occur on any species of Madrepora, Oculina, or
other corals with a similar method of branching. Is there
some special scent or flavour in the Seriatoporidae which
attracts the crabs to these corals ? This is a question to
which no satisfactory answer can be given at present.

Fig. 35. — An example of Seria-
topora, ill which some of the
branches have coalesced to form
a gall for the crab Hapalocarcinus.
Nat. size.

MADREPORARIAX CORALS 85

A few words must now be added on the difference be-
tween the two genera.

Seriatopora. — vSeriatopora can usually be distinguished
at once from Pocillopora by its slender and sharpl}^ pointed
terminal branches (Fig. 34) . The calices are arranged in longi-
tudinal rows on all sides of the branches and in some species
show a margin raised above the level of the coenosteum. The
two directive septa form a prominent ridge on the floor of
the cup, and this ridge is always parallel with the axis of the
branch. It may be a matter of dispute whether the middle
part of this ridge should be called the columella, but the
most reasonable point of view seems to be that there is no
columella. The other septa are often very rudimentary
and difficult to see. In some specimens there are only four
and in others eight, or if we count the two directive septa,
six or twelve in all.

The colour of living Seriatopora on the reefs is usually
pink, but yellow varieties have been found. In some cases
the polyps appear as brown spots on the branches.

Pocillopora. — In Pocillopora the method of branching
is coarser and more irregular than in Seriatopora, and the
terminal branches are thick and blunt at the apex, never
being drawn out into fine points. The surface of the branches
is very rough and in many species raised into a series of
little mounds or verrucae. The calices are very numerous,
and as compared with Seriatopora v'ery close together, so
that in many places they are actually in contact with one
another. The study of the septa of these minute calices is
beset with even greater difficulties than in Seriatopora,
because in many specimens their cavities are filled up with
a chalky deposit (stereoplasm), which completely hides the
structures buried in it and cannot be removed by the
ordinary cleaning reagents. However, when a terminal
branch of a good specimen is examined in a strong light with
a lens, a ridge formed by the directive septa and parallel
with the axis of the branch can usually be made out. A
more detailed examination of this ridge with a higher power,
however, shows that in the middle of it there is usually a
definite but small papilliform columella. In addition to the

CORALS

two directive septa there are four other hirge septa alter-
nating with six smaller ones. The colour of living colonies of
Pocillopora is usually green, sometimes " a most brilliant dark
green " (Gardiner). Other colonies are colourless or pink.

Stylophora. — The genus Stylophora (Fig. 36) is not an
uncommon coral on the reefs of the Indian and Pacific Oceans,
and calls for a few words of comment, because, in some
respects, it has a superficial resemblance to varieties of the
Hydrozoan genus Stylaster (p. 153).

As the name suggests, the most characteristic feature it
exhibits is the prominent pillar-like columella
(Fig. 37), which stands up in the centre of the
calyx, and as this feature is combined with
that of narrow and usually rather thick septa
the calyx has some resemblance to a pore
cycle of one of the Stylasterina. A critical
examination of a calyx shows, however,
that the spaces between the septa are not
pierced by dactylopores and that the six
thick primary septa are supplemented by
six thinner rudimentary ones.

Stylophora is undoubtedly a Madre-
porarian coral, but the authorities are not
agreed as to its exact systematic position
and generally place it with Madracis in a
separate family — the Stylophoridae ; but it
agrees so closely in many important char-
acters with Seriatopora that there seems to be no sufficient
reason for excluding it from the family Seriatoporidae.

The form of the corallum is usually arborescent, the
branches ending in thick blunt points, but sometimes it is
palmate or encrusting. The substance is hard and compact
except in the ax-is of the larger branches, where it becomes
porous, and the ends of the growing points, where it is per-
forated by calicular pores.

The small calices are separated by a considerable amount
of coenenchym, which is adorned with a great number of
small blunt tubercles giving it a granular appearance. In
some specimens these tubercles fuse to form ridges. The

Fig. 36.— Stylo-
phora. The ter-
minal branch of a
colony from the
Indian Ocean, x 2
diams.

MADREPORARIAN CORALS

calices are about i mm. in diameter and project slightly
and obliquely from the surface so that the disc of the polyps
when expanded is directed upwards towards the apex of the
branch on which they are situated. There are six thick
but rather narrow primary septa, and in some calices six
thinner secondary septa can be seen. The most prominent
feature of the calyx is the
strong pillar-like columella.

The cavity of the calyx is
shallow and shut off below
by a thin calcareous plate.
Below this plate the corallum
is pierced by a long cylindrical
pore divided into a number
of chambers by transverse
tabulae (Fig. ^^y). According
to some authors the endotheca
is in the form of irregular
dissepiments, and possibly it
varies in different species or
in different conditions, but in
the specimen from which Fig.
;^y was drawn the pores were
distinctly tabulate.

The polyps of Stylophora
possess twelve capitate ten-
tacles, six larger and six
smaller ; and there are almost
invariably twelve mesenteries,

of which two pairs are directives. The polyps are connected
with one another by a thin coenosarc, which lies entirely
above the coenosteum, and in its lower layer there is a
network of canals running between the tubercles as in
Seriatopora.

Family 7. Madreporidae

The corals belonging to this family constitute the most
dominating feature of modern coral reefs, and probably
contribute, by the activity of their polyps, a larger propor-

FiG. 37. — Stylophora. Upper
figure showing the surface of the
coral. Lower figure showing the
calices in vertical section, x circa 25
dianis.

88 CORALS

tion of the calcareous substance of which the reefs are com-
posed than any other group of corals. They are, however,
of comparatively recent origin, as the}^ do not seem to have
attained to any degree of importance as reef-builders until
the later Tertiary times, when they overtook and replaced
to a great extent the Astraeidae and other groups of imper-
forate corals in the struggle for existence on the reefs. The
cause of this change of dominance may be due partlv to
the rapidity of growth and partly to the extraordinary
plasticity in form of the Madrepores as compared with other
corals.

The construction of a perforated corallum requiring the
secretion of a relatively small amount of calcium carbonate
for a given surface of support for the polyps and the pro-
vision of an elaborate system of coenosarcal canals, usualh'
crowded with active zooxanthellae, are characters which un-
doubtedly assist phj-siologically in rapid growth.

The complex of conditions which renders some coral reefs
of the tropical seas more favourable for the growth of
Madrepores and others less so is so intricate that it will
prove to be a very difficult tangle to unravel. The mean
temperature of the water, the violence of the breakers on
the shore, the abundance and character of the food supply of
microscopic organisms, and the chemical constitution of the
sea-water are factors which, in varying combinations, deter-
mine whether a particular kind of coral shall predominate
on a reef. On one reef may be found an abundance of
Madrepores, on another Heliopores and Astraeids, on another
little more than a carpet of Lithothamnion or some other
form of calcareous Alga ; but taking the reefs of the world
as a whole, there can be little doubt that the three genera,
Madrepora, Porites, and Montipora, do maintain the premier
position in abundance and in luxuriance of growth on the
coral reefs of the present day.

It is in this family also that we find, in a more exaggerated
form, perhaps, than in any other, the difticulty of dividing
up the genera into specific groups.

The careful study of a single large colony or of a collection
of specimens from the same locality reveals so much variet}'

MADREPORARIAN CORALS 89

in general form, in the size of the cahces, and in other char-
acters which are available for the determination of species,
that the task of the conscientious systematist seems to be
a hopeless one. No attempt can be made in these pages to
help him.

But there is one consideration of this problem which is
worth bearing in mind, and may be of more general interest.
If we consider a large collection of specimens of a Madrepora
from a given reef, we may regard the differences we observe
between them to be due either to characters inherited by
them from their parents or to the moulding and fashioning
effects of external forces that have played upon them from
the time when the ciliated larvae from which they have
sprung first settled down upon a rock.

If it were possible for us to experiment by breeding
Madrepores, as we breed mice or canaries, we could determine
whether these differences are inherited or not. But at
present the difficulties in the way of making pure cultures
of these corals seem to be insuperable.

In the absence of such direct experimental evidence,
which can alone decide the matter, it is open to us to hold
the opinion that the variations are due to local environ-
mental conditions, and on this assumption we may hold
that in such a genus there has been no subdivision into a
large number of distinct specific groups, but only one large
and very variable species is represented.

This view has not been proved to be correct or incorrect,
but if it is correct, then we have a species which shows
extraordinary powers of adapting itself in various ways to
the complex of local conditions, and it may be that this
adaptability or plasticity, as it is sometimes called, is an
important character in gaining for the species its predomi-
nance on the reefs.

The word madrepore ^ was first used by Imperato in 1599,
and there can be little doubt that the coral which he called
Madrepore was the Mediterranean coral now called Dendro-

1 The word madrepore has been frequently translated " Mother stone "
{Porus )natronalis), but should be translated " JMother of stone." Cf. Ital.
Madreperla = Mother of pearl.

90 CORALS

phyllia raitica. Marsigli and other writers of the early part
of the seventeenth century extended the apphcation of the
word to other white stony corals, and thus it came to be
given by Brown, in 1756, to a coral which can be definitely
recognised as a specimen of a coral having the characters
of the modern genus Madrepora. Brown's specimen came
from Jamaica, and he called it " Madrepora ramosa major
muricata et stellata aperturis cavernarum minoribus
depressa." Most unfortunately Linnaeus, in his Svstema
Naturae (loth ed.), published in 1758, changed the name
to Millepora muricata, but corrected the mistake in the
twelfth edition of the same work and called it Madrepora
uiuricata.

The generic name Madrepora was accepted and used in
the important treatises on corals by Lamarck, Milne-
Edwards and Haime, and in more modern times by Brook
and Bernard, the authors of the magnificent British Museum
Monographs on Madreporarian corals, and by many other
naturalists. It has been declared, however, that in conse-
quence of the blunder made by Linnaeus in 1758, the name
Madrepora should be abandoned and the genus given the
name Acropora, originally proposed by Oken in 1815. It
would be, in my opinion, a most grievous mistake if this
suggestion were universally adopted. The meaning of the
word Madrepora has become so definitely fixed by all the
great men of science who have studied and described the
anatomy of the hard and soft parts, and the species and
varieties of form found in the genus, that a change of name
will only lead to confusion in our literature. No more
mischievous and senseless example could be chosen to
demonstrate the absurdity of strict adherence to the so-
called Law of Priority than the proposed change of the name
Madrepora to Acropora.

Madrepora is probably the most widely distributed and
most abundant of all the reef-building corals of the world.
On many of the reefs of the Indo-Pacilic regions specimens of
the genus seem to form an almost continuous carpet of coral,
extending for miles along the coast-line, and in many places
the water at low tide just beyond the edge of the reefs is

MADREPORARIAN CORALS 91

filled with forests of the branches of specimens which are
rooted on the rocks of the sea-bottom.^

The specimens the naturalist finds exposed at low spring
tide do not as a rule attain to the same gigantic proportions
as the massive Porites, but the branching specimens in
deeper water outside the reef must be often many feet in
height, with main stems nearly a foot in diameter. Massive
colonies twenty to thirty feet in length are also found in
some localities.-

The genus is found both in the West Indies and in the
Indo-Pacific Ocean, the limits of its geographical distribution
being almost identical with that of the coral reefs of the
world. The forms assumed by the colonies are so varied
and so much influenced by the local conditions and surround-
ings that it is quite impossible to express in a few words all
the possible varieties of shape that a colony of Madrepora
may assume. There are, however, three types of construc-
tion which may be recognised in a large collection of these
corals, known respectively as Forma paUnata, Fonna pro-
lifera, and Forma cervicornis.

In Forma palmata the colony arises from a short, thick
stem attached to its support by a spreading or encrusting
base, and divides rapidly into a number of branches which
ramify and anastomose to form a fan-shaped or leaf-like
frond, erect, oblique, or at right angles to the stem from
which it arises.

In Forma prolifera the branches arising from a short
stem divide and ramify to form an irregular bush-like
growth, with usually less anastomosing of the branches than
in Forma palmata.

In Forma cervicornis there is usually a long, thick, erect
main stem, from which large, irregular, lateral branches are
given off, which subdivide and but rarely anastomose. This
form has the popular name Stag's-horn coral.

There are many intermediate forms between these three
types and others that are massive, lobate, encrusting or
lamelliform, and seem to be quite distinct.

^ See photographs in Saville-Kent's Great Barrier Reef of Australia.
^ Reference may be made to the large specimens in the British Museum.

CORALS

As the general form of the colony of Madrepora is so
variable, it affords no characters by which the genus can be
safely distinguished from others. A close examination of
one of the terminal branches is necessary to find characters

to be relied upon for this
purpose, and fortunately
these characters are so
definite that it is nearly
always quite an easy
matter to determine for
certain whether a given
coral is or is not a member
of the genus Madrepora.

Each terminal branch
bears at its extremity a
single large apical cah'x,
and below this a number
of oblique calices of
smaller size, arranged like
a series of brackets on all
sides of the branch. The
smallest of these brackets
are next to the apical
calyx, the largest ones
farthest away from it (Fig.
j8). In some varieties
the apical calyx is thick-
walled and dome-shaped,
so that the terminal
branches are blunt or
knob - like. The lateral
calices have in these
varieties more definitely
the appearance of being arranged in a radial manner round
a very thick-walled axial calyx. Such varieties are some-
times regarded as belonging to the sub-generic groups Isopora
and Tylopora. More rarely the axial calices are more or
less laterally compressed and the lateral calices arranged
principally in two series (sub-genus Distichoc^'athus).

Fig. 38. — ^Madrepora. .-\. tcrniinal branch
of a large colony of a Stag's-horn variety.
;■: 2 diams.

MADREPORARIAN CORALS 93

If, now, the terminal branch of the commoner type of
Madrepora be broken off and the surface of the fracture be
examined, it wiU be found that in the axis of the branch
there is a cavity traversed by radial septa which are con-
tinuous with the septa of the apical calyx.

It follows from this observation that the terminal branch
represents the elongated calyx of a polyp which has given
rise, by centrifugal gemmation, to a number of lateral polyps.
The growth and fusion of the walls of the lateral polyps
completely enshroud the calyx of the apical polyp which has
given birth to them, and there is no common substance or
coenosteum between them.

The number of septa in the lateral calices is usually six,
and of these the two directive septa situated in planes which
are radial to the axis of the branch are decidedly larger than
the others and frequently meet in the centre of the calyx
(Fig. 6, p. 32, DS). There is no columella. The apical
calices have usually more than six septa, and in some cases
the lateral calices have also more than six septa, but the
number of septa seems to have reached its maximum when
twelve have been formed, and calices with more than twelve
septa are very rarely found. The character of the endotheca
is very variable, but it is noteworthy that in some cases it
takes the fomi of more or less regularly disposed tabulae.

The polyps of an expanded Madrepora appear to be of
two distinct kinds. The apical polyps, projecting some
3 mm. beyond the apex, of the branch, have only six long
tentacles, and the lateral polyps, which project very little
beyond the lip of the calyx, have twelve tentacles, six long
and six short. But this does not seem to represent a true
dimorphism such as we find in the polyps of many of the
Hydrozoa and Alcyonaria, because at the rapidly growing
margins of the colony many intermediate forms between
the two kinds may be found, and it seems probable that a
polyp of the twelve-tentacled kind may change into a polyp
of the six-tentacled kind when it assumes the function of an
apical polyp and starts the development of a new branch.

The tentacles seem to vary a good deal in character.
Sometimes they are simply digitiform, sometimes they

94 CORALS

terminate in a swollen apex and are capitate. Sometimes
they are marked with white spots representing batteries of
nematocysts, sometimes these spots are not noticeable. In
retraction the tentacles may be introverted, but there is
not sufficient evidence to prove that this is always the
case.

The number of mesenteries is nearly always twelve in a
full-grown polyp, and every polyp has two pairs of directive
mesenteries (Fig. 6, III, III, and IV, IV, p. ;^2).

In some polyps additional mesenteries are formed in a
manner which seems to be peculiar to Madrepora, Porites,
and possibly some of their allies. Instead of being added in
unilateral pairs right and left of the directive mesenteries,
as they are in the Astraeidae, they are added in bilateral
pairs within the space between the two directives of a single
pair of directives (Figs. 9 and 10, p. 35).

The colours of living Madrepores are so varied on different
reefs and on different places on the same reef that it is
difficult to make a general statement on the subject which
can be of any value for the collector.

According to Duerden the colours of the Jamaican
Madreporas vary but little. Colonies as a w^hole are lighter
or darker shades of brown, becoming green, yellow, or orange.
According to Saville-Kent, the different varieties of Madre-
pora on the Great Barrier Reef exhibit almost every possible
colour variety from pale yellow through shades of green,
pink, and brown to lilac and blue. On the coral reefs of a
small island off the coast of Celebes, the Madrepores on one
side of the island, which was more exposed to the surf,
seemed to be uniformly brown, but in the calmer waters of
the other side of the island there was much greater variety,
the lilacs, bright greens, and yellows predominating. One
of the most striking colour features of these corals is the
brightness of the colours of the points of the branches.
When seen from a boat through the clear sea-water on a
bright, sunny day, these emerald green, pale yellow, lilac, or
sometimes white terminal branchlets produce a most fascinat-
ing and startling effect even in a background that is itself
a feast of brilliant colour schemes. When the tide falls,

MADREPORARIAN CORALS 95

however, and the corals are exposed for a time to the sun,
the briUiancy to a great extent disappears, and a uniform
duhness of brown and yellow seems to prevail.

PoRiTES. — The genus Porites is another very important
reef-building coral widely distributed in the tropical seas of
the Old and New World. In some seas, blocks of Porites
reach to an enormous size,^ and appear to be the principal
factors in the construction of the reefs, but in others the
Porites rocks occupy a subordinate position to the colonies
of Madrepora, and relatively small blocks of it are scattered
about in more or less isolated positions.

The forms assumed by the large colonies are almost as
varied in Porites as they are in Madrepora ; but in Porites
massive, spherical, lobate, and encrusting forms are more
characteristic. Ramified forms are found, but the branches
are generally thick and terminate in blunt knobs. The
ramification is seldom profuse.

The surface of the corallum is seen to consist of a very
large number of small calices with common pentagonal
thecal walls (Fig. 39). There is no coenosteum between the
calices. The septa are twelve in number and the directive
septa are not usually distinguished from the others by their
greater size. All the septa are so profusely perforated that
each one has the appearance of a lattice work of trabeculae
rather than that of a perforated lamina. On the free border
of the septa there is a row of blunt spines, and on their
inner side there is a cycle of pali. In the centre of the calyx
a single spine represents a columella. At the base of the
calyx the septa are often seen to be connected by syn-
apticula. The substance of the corallum below the surface
has usually the appearance of a most intricate maze of
trabeculae, but frequently the cavities become filled with
stereoplasm and, less frequently, the trabeculae show a
tabular arrangement.

The living polyps of Porites project but slightly from
the calices. The tentacles are usually twelve in number,
digitiform or acute in specimens in Jamaica (Duerden), or

^ For example, the great mass of Porites, 30 to 40 feet in diameter,
described and photographed by Saville-Kent.

96 CORALS

distinctly capitate in Australian Barrier Reef specimens
(Saville-Kent).

The arrangement of the mesenteries in Porites is very
similar to that previously described in Madrepora, and the
increase in the number of mesenteries also takes place by
the addition of bilateral pairs in the space between the
mesenteries of one pair of directives.

The colour of the Porites is very variable and often
very brilhant. Duerden ^ writes that "Porites astraeoides
(of Jamaica) is one of the most gaily coloured of all the
West Indian corals, and occurring in large masses often
becomes an important constituent in determining the general
coloration of the reefs. As a rule the colonies are a bright
blue, pale yellow, or yellowish-green. Various colours occur
side by side, and sometimes one portion of a colony will be
blue and another yellowish-green."

Saville-Kent says of the colours of Porites on the Great
Barrier Reef, " A light ochre, dark and golden or mustard
yellow, and brown are the prevailing colours among the
arborescent types. The surface of the corallum in the
massive species, however, is often a delicate pink, a light or
bright lilac, or (more rarely) pale yellow."

The genus Goniopora is closely related to Porites and
also builds up great masses of spherical, lobate, encrusting
coral. It appears to be more restricted in its recent geo-
graphical distribution than Porites, being confined to the
tropical Indo-Pacific regions. The principal characters by
which it can be distinguished from Porites is the presence
of a secondary series of twelve septa, so that there are
twenty-four septa in each calyx instead of only twelve.

The polyps are said to be very extensile and to possess
usually twentv-four long digitate tentacles arranged in a
single ring.

We have at present no knowledge of the number and
arrangement of the mesenteries or other details of anatomical
structure.

MoNTiPORA. — The genus Montipora is another important
reef-building coral, widely distributed in the tropical seas of

^ J. F. Duerden, Mem. Nat. Acad. Sci. Washington, vol. viii., 1902, p. 550.

MADREPORARIAN CORALS 97

the Old World, but absent in the Atlantic Ocean and West
Indian waters. Many specimens are of very great size, and
almost every possible form of growth such as the branching,
encrusting, massive, foliate, etc., may be represented. One
particular form of this coral was called by Rumphius
Elephant Ear and others Sea-rose or Sea-cauliflower. These
varieties are described by Pallas under the name Madrepora
joliosa.

There is no difftculty in determining at once, by the
examination of a dried specimen with a hand lens, that all
parts of the colony are profusely perforated.

The calices are small, rarely exceeding i mm. in diameter,
and do not project above the general surface of the corallum.
The genus can be distinguished from Porites, with which it
is most likely to be confounded, by the presence of a con-
siderable amount of coenosteum between the calices, per-
forated by numerous and relatively large pores.

The details of the calicular structure are more difficult
to ascertain, not only on account of their small size, but
because the septa are reduced by perforation to rows
of minute spines or trabeculae of great variability. An
examination of a large number of cahces, however, leads to
the conclusion that six primary septa are always represented
and usually six secondary septa as well. In some specimens,
but not in all, the two directive septa of the primary series
are larger than the others and meet in the centre of the calyx.

According to Saville-Kent the colours of Montipora on
the Barrier Reef are almost as brilliant and as varied as the
colours of Madrepora.

Anacropora, a genus confined to Indo-Pacific seas, is in
some respects intermediate between Madrepora and Monti-
pora. It has a characteristic method of growth, thin branches
diverging at wide angles which tend to form tangled masses
of low growth.

The walls of the calices protrude from the surface, and
there are definite septa and costae as in Madrepora, and the
calices are separated by coenosteum as in Montipora.

TuRBiXARiA. — The genus Turbinaria is generally classified
with the Madreporidae. It differs, however, from the other

CORALS

membcis of this family in some important particulars, and
it is possible that when we have a more extended knowledge
of its anatomy it may have to be considered as the type
genus of a separate family.

The name is derived from the shape assumed by the
most common variety or species of the genus, which is that
of a large shallow bowl attached by a thick stem to the
rock. The genus is widely distributed in shallow water in
the Indian and Pacific Oceans, but does not occur in the
West Indian waters.

It seems to be a characteristic feature of the genus that

in the early stages of its growth
it has a shape like a mushroom
with a flat or slightly concave
disc and a ring of calices round
the margin (Fig. 40).^ By mar-
ginal growth, these calices become
situated on the upper side of the
disc, and are succeeded by others
that are formed on the growing
edge. This process is continued
until the bowl shape is attained

(Fig- 41)-

The other varieties of form
assumed by the adult corallum
seem to be due to irregularities
in the growth of the margin, and
thus great sheets of Turbinaria are formed with fringed
or foliate edges, plates, or dishes which seem to have lost
the original stalk and form encrusting laminae over the rock
or over other laminae of the same coral. Colonies of this
genus which ramify in the manner of the Madrepore and
other corals, are not common, but do occasionalh' occur.
The corals of this genus also reach great dimensions. A
specimen in the British Museum of irregular shape with a
boundary of 16 ft. 8 in. is 1500 lbs. in weight. -

The upper surface of the corallum is provided with a

^ Pace, /. I.itnt. Soc. .x.wiii. p. ^6i.
2 F. J. BelC J.n. Micr. Soc. 1S95, p. 148.

Fig. 40. — Turbinaria. A young
stage in the dc\-elopnu-nt of a
colonv. Xat. size.

° «

o -^

03 <D

O <l>

^ -^

> -a

o ^

03 -^

MADREPORARIAN CORALS 99

large number of calices, which usiiany project a httle from
the general surface, and between them there is a variable
amount of profusely perforated coenosteum which is not
marked with ccstal ridges.

The surface of one of these large Turbinarias affords an
interesting study in variation. The student finds on the
same frond calices that vary in size from 0-5 mm. to i-o mm. ;
he finds that some calices project from the surface with
thick cup lips and others are almost flush with the surface,
and that in some parts of the corallum the calices are
crowded together and in others are separated by consider-
able areas of coenosteum.

A similar excessive variation is also seen in the details
of structure of the calices. The number of septa rarely
exceeds twenty-two, but any number from seventeen to
twenty-two may be crowded in a full-grown calyx. The
septa are usually of approximately equal size, so that it is
impossible to recognise the directive septa or to distinguish
the primaries from the secondaries. The most remarkable
feature of the septal system, however, is that the number
of septa does not seem to bear any relation to the number
twelve, and it is this pecuKarity which renders the position
of the genus in the family Madreporidae a doubtful one.
A columella is usually present, but it is also very variable.
There are no pali.

The pairs of mesenteries of Turbinaria correspond in
number with the septa. There are two pairs of directive
mesenteries arranged in a plane almost parallel with a radius
of the colony. The number of other pairs of mesenteries
varies and is not the same on the two sides of the directive
plane.

According to Saville-Kent " the tentacles are numerous
and simply subulate," and the colour of some of the varieties
is rose-pink or yellow.

It has been supposed that in an early stage of the develop-
ment of a Turbinaria colony there is an important difference
between this genus and Madrepora. It was suggested that
whereas in Madrepora the primary polyp and the calyx it
forms becomes the axial polyp on the sides of which the

100

CORALS

young buds are formed, in Turbinaria the primary polyp
is suppressed and becomes engulfed in the corallum at a
stage such as that shown in Fig. 40. Pace has shown,
however, that the primary calyx does persist, but instead
of standing up straight from the base it bends to one side
and therefore appears in that stage as one of the marginal
calices.

Notwithstanding this peculiar character, and others
which have been already mentioned, the general characters
of the profusely perforated corallum and the structure of
the calices do not justify the removal of the genus from the
family Madreporidae in the present state
of our knowledge, but our knowledge is
still very imperfect, and a detailed study
of the structure of the polyps and particu-
larly of the method of gemmation might
lead to results of importance which would
definitely settle the position of the genus
in our system.

Fig. 42. — PyrophyU

Ua inflata. P"sian PyROPHYLLIA.1— A ^g^US of UUkuOWn

Gulf, 150 latnoms. o

X 8 diams. From affinities. A remarkable little solitarv

fZ'gT' ^^""""'' coral not more than 5 mm. in length b>'

I mm. in diameter was found in a sample

of the sea-bottom obtained by Mr. Townsend in the Persian

Gulf at a depth of 156 fathoms (Fig. 42).

Its most characteristic feature is that it exhibits almost
perfect octo-radial symmetry. There are eight large septa
(the protosepta) and eight small ones (the metasepta),
never more nor less (Fig. 43). In the centre of the calyx
there is an undulating laminate columella. Externally,
the thecal wall is marked by from fifteen to twenty annular
ridges, which may be considered to indicate a series of
intermittent stages of growth, and there are sixteen costal
spines and crests on each annulus corresponding with the

1 S. J. Hickson, Pyoc. Zool. Soc, 191 1. P- 1037.

MADREPORARIAN CORALS loi

septa. The shape of the coral is that of a sHghtly bent
cone with an inflation at the apex. The apex of the cone
is, of course, the base of the coral, and is the part which
is formed first in development.

This inflated end of the Pyrophyllia is of some special
interest, because it is obviously not adapted for attach-
ment to a support — and indeed never shows any signs of
attachment. This lea^s to the conclusion that the living
Pyrophyllia is a free coral, but if it is free where does
it live ? It is inconceivable that it lives upright among
the loose rubble of shells with which it was found. It must
have come therefore with the currents from some other
localit}^ or have fallen from the
surface waters. ^^ f ^Ts.

Unfortunately we have no /^^ \ Av

information concerning the / v ^\ ^'^

habitat or anatomy of the T"*""^^ I -. .^^ — h c

polyp that forms this coral, ^' V" ^ \ I
and every one of the many \/ , \ ^X^

hundreds of specimens that ^^—4—-'^^^'^

were obtained were more or

, u 1 ¥iQ. 43. — Diagram of the septa

less water - worn or broken. oi Pyrophyllia inflata. c, columella;

Until the hving polvp is dis- :^.s., primary septa ; m.s., secondary

1111 • septa. From Manchester Memoirs. ^

covered we shall have no satis- 54, 1910.

factory answer to the many

questions that arise concerning Pyroph3'llia, but it is possible

that the dilated base enclosed a bubble of gas which kept it

suspended in the water, and that the habit of this coral is

pelagic.

It is very diificult at present to determine the zoological
position of this interesting genus.

The only recent coral that appears to be related to
it is Guynia annnlata ^ from 92 fathoms of water on the
Adventure Bank, in the Mediterranean Sea, which Duncan
considered to be related to a family of corals belonging to
the extinct Order Rugosa. There are, however, some im-
portant differences between Guynia and Pyrophyllia which

1 P. M. Duncan, " The Structure and Affinities of Guynia auuiilata,''''
Phil. Trans. Roy. Soc, 1872, p. 29.

102 CORALS

render the relationship very obscure. Guynia has the same
annular ridges of growth, and it has usually the same number
of large and small septa, but it is attached by its side to
shells and has no inflated base.

The only other coral with which it seems to have any
true relation is the extinct genus Conosmilia from the
Tertiary deposits of Australia.

CHAPTER V

ALCYONARIAN CORALS

" Qui navigavere in Indos Alexandri milites frondem marinarum
arborum tradidere in aqua viridem fuisse, exemptam sole protinus
in salem arescentem, iuncos quoque lapideos perquam similes veris
per littora." — Pliny, N'at. Hist. xiii. cap. 51.

The large group of marine organisms known as the Alcyo-
naria has received its ordinal name from a common spongy
zoophyte called Alcyonium which is found in shallow water
and sometimes above low-water mark on the British and
other European coasts.

Lumps of dead Alcyonium, with their four or five lobate
processes, which have been washed ashore, have a very rough
resemblance to a human hand with swollen and distorted
fingers, and on this account the British species was given
by Ellis the name Alcyonium manits marina, and is known
in popular works on natural history as " Dead Men's
fingers."

But we are not concerned in this book with Alcyonium,
for although it does secrete calcareous spicules to support
its structure it is relatively soft or spongy in texture and
could not be brought within the scope of any recognised
definition of the word coral.

However, Alcyonium is closely related to many other
marine zoophytes which do form a hard continuous skeletal
structure which have been and still are called " corals " ;
in fact, the well-known precious coral of commerce, the
first of all others in history to receive the name coral, is a
member of the group. As the Alcyonaria form a very
well-defined Order of the Animal Kingdom, notwithstanding

103

104

CORALS

the great variety they exhibit in the form and texture of
the skeletal structures they produce, it is necessary to
relate in a few words some of the anatomical characters
which distinguish them.

As with many other corals, the Alcyonaria are colonial
in habit ; a large number of animal organisms of the form
known as Polyps, in organic connexion with one another
by a system of nutritive canals, constitute the structure
which is known as the Alcyonarian. In most of the Alc^'O-
naria all the polyps of a colony have a similar anatomical
structure, showing when fully expanded eight pinnate

Fig. 44. — Diagram to illustrate the structure of a dimorphic Alcyonarian.
Aut., autozoid ; C, endodermal canals; il//., mesenteric filaments; St., siphono-
zooids ; St., stomodaeum.

tentacles (Fig. 47, A.) and a general octoradiate symmetry
of their organs, but in some genera, which are usuallv more
spongy in texture than the others, there are in addition to
the normal polyps or autozooids a large number of polvps
which are arrested in development and never produce anv
tentacles. The latter are called the siphonozooids, and
their primary function appears to be to create and maintain
by means of ciliary action a flow of water through the canal
system (Fig. 44).

Another character of the Alcyonaria, with verv few
exceptions, is the power of forming calcareous spicules.
These spicules, varying greatly in size, shape, and distribu-

ALCYONARIAN CORALS

105

tion in the colony, afford one of the principal characters for
the recognition of genera and species (Fig. 45).

In many cases the spicules cease to grow when they have
reached a certain size and remain free from one another in
the soft tissues, so that when the colonies die and the soft
tissues are dissipated the spicules are distributed. But in
others {e.g. Corallium and Tubipora) the spicules grow until
the}' come into contact with one another and become tightly
packed together. In this way a skeletal structure persists
after death which represents the general form of the colony.

The genus Heliopora
stands by itself as the
only recent Alcyonarian
that forms a continuous
calcareous skeleton with-
out spicule formation after
the manner of the Madre-
poraria.

In another group of
Alcyonaria which may be
called the Gorgonians, the
substance Keratin, closely
allied to horn, enters into
the composition of the
skeletal structures. In
Gorgonia itself, an axis is

formed of pure keratin,. and this supports a thin crust or
bark consisting of the polyps, with their connecting tissues
and the calcareous spicules. On the death of the colony
the bark is dissolved and washed away by the sea, the
horny axis alone remaining intact.

In some Gorgonians the horny axis is impregnated with
calcium carbonate, and in others the axis consists of alternate
horny nodes and calcareous internodes.

There are a few Gorgonians which consist of a long
unbranched stem attached by a disc-shaped expansion at
the base to a foreign substance, but usualty the main stem
divides into secondary branches, and these ramify again
and again before they terminate in numerous delicate free

9 V-** oXK"^?^*

^r^ T

Fig. 43. — Spicules of Alcyonaria. A,
Melitodes : B, Isis ; C, Gorgonia ; D,
Echinomuricea.

io6 CORALS

twigs. In some forms the branching takes place in all
directions, forming bushy or tree-like structures, but more
commonly the branching is in one plane only, so that the
structure is fan-shaped or flabelliform.

The presence of the horny substance in the axis of the
Gorgonians is of advantage to them in man}/ sea localities
where the tides and currents are particularly strong, in that
it gives them the power to bend without breaking, the
calcareous skeleton of the purely calcareous Alcyonaria
being quite inflexible. In the tropical seas it is a wonderful
sight to see through a few feet of the clear water the great
tufts of brightly coloured Gorgonians attached to the piles
of a pier, or in favourable situations on the reef waving
backwards and forwards with the rise and fall of the water.
An intelligent observer seeing them for the first time would
probably be inclined to classify them with the other corals
of the neighbourhood, but would notice that they differ
from them in their flexibility.

The Gorgonians, however, are not the only coral-like organ-
isms that are flexible, and the famous work by Lamouroux
published in 1816, entitled Poly piers coralligenes flexihles,
included Algae, Polyzoa, Hydrozoa, as well as some of the
Anthozoan corals. Nevertheless the popular expression
" flexible corals " has become more restricted, and is still
sometimes used to signify only the Alcyonarian corals with a
horny flexible axis.

In the course of the descriptions that are given of
different kinds of Alcyonarian corals reference will be made
to their colours. These colours are, as a rule, due to a pig-
ment in the calcareous spicules which is permanent, that is
to sav, it does not fade or disappear when the coral is dried.
The permanence of these colours is really remarkable, as is
exemplified by the colour of the red coral beads in the
ancient British shield found in Lincolnshire (see p. 241),
which is probably as bright now as it was several hundreds
of vears before the Christian era, when the coral was dredged
up from the sea. The Alcyonarian polyps when fully ex-
panded in the seas are usually either transparently white
or of a faint pale pink colour, and when they are retracted

ALCYONARIAN CORALS 107

the corals have very much the same general colour in the
sea as they have when dried and stored in a museum.

There are, however, some exceptions to these general
rules (see Primnoa, p. 129, Tubipora, p. 112).

In the Madreporaria, on the other hand, the colours are
almost invariably due to a pigment diffused through the soft
tissues which is soluble in alcohol and fades away soon after
the death of the corals. Dried and preserved Madreporarian
corals, therefore, never show the nature of the brilliant
colours they may exhibit when they are alive.

It is interesting in this connexion to notice the difference
there is between the exhibits in the cases of a museum of
the Alcyonarian and Madreporarian corals. On the one
hand, we have an endless variety of bright colours and on
the other a monotonous dull stony white.

CoRALLiUM.^ — The first coral mentioned in literature;
and the most famous throughout the ages for its beauty and
for the occult powers it was supposed to possess, is the red
or precious coral of the Mediterranean Sea. In another
chapter will be given a short account of the history of the
trade in this substance and of the myths concerning its
origin and properties. Here we are only concerned with the
study of the red coral from the zoological point of view.

The hard red coral substance that is sold in the shops
is the axis or central supporting core of a dimorphic colony
of Alcyonarian polyps. When the coral is alive, this axis is
covered by a soft bark or crust, through which penetrates an
elaborate system of canals, which bring the two kinds of
polyps, the Autozooids and Siphonozooids, into communica-
tion with one another (Fig. 46).

When a colony of Corallium that has been just removed
from the sea is placed in a glass vessel and allowed to remain
there for a little while, the white and almost transparent
autozooids gradually expand and project from the surface
of the bark, producing an effect which the earlier naturalists
mistook for the flowers of a plant (Fig. 47). Each autozooid
bears a crown of eight pinnate tentacles, formerly regarded

1 See the beautifully illustrated memoir by H. de Lacaze-Duthiers,
Histoire naturelle du Cor ail, Paris, 1864.

io8

CORALS

as the petals of the flower, and through the transparent
cyhndrical body wall may be seen thread-like structures,
which on further microscopical examination prove to be the
throat (stomodaeum), the eight mesenteries, and the eight
mesenteric filaments of a typical Alcyonarian polvp.

In the months of May and June the autozooids contain a
number of spherical or oval bodies, and occasionally one of
them will squeeze through the mouth and swim away.

Fig. 46. — A diagram to show the
structure of a branch of Corallium as seen
in transverse section. In the centre is the
axis (Ax.) and covering this is the coenen-
chym, a soft fleshy substance containing
the endoderm canals and spicules and bear-
ing the autozooids (A.) and the siphono-
zooids (S.). :■. 4 diains.

Fig. 47. — Corallium nobilc. Medi-
terranean Sea. A., an expanded
autozooid. S., a siphonozooid. From
a drawing by H. de Lacaze-Duthiers.
.■ about 8 diams.

These are the larvae, for CoralHum presents us with one of
the rare examples of the occurrence of viviparity in the
group of the Alcyonaria. Corallium nolile of the Mediter-
ranean is also rather exceptional among corals in being
hermaphrodite. Some branches of a single specimen may
be male and others female, or a single branch may support
both male and female polyps.

When all the autozooids are fully expanded, the out-
stretched tentacles form an almost complete gauzy veil over
the surface of the branch, so that no minute organism that

ALCYONARIAN CORALS

109

swims within a polyp's length of the coral can possibly
escape the batteries of nematocysts with which the tentacles
are armed.

Between the autozooids a number of small yellowish-
white spots can be seen, each of which is provided with a
little mouth when the coral is alive and expanded. Until
recently these spots were thought to be young polyps which
develop into autozooids, but it was shown by Moseley that
they are a different kind of polyp, and perform a different
function from the polyps which expand (Figs. 46 and

47, S.).

They are called the siphonozooids. They have no
tentacles and the mesenteries are very much reduced, but

Fig. 48. — Diagram of a transverse
section through an Alcyonarian polyp.
St., stomodaeum ; Dm., dorsal mesen-
teries ; I'm., ventral mesenteries.

Fig. 49. — The same, taken at a
lower level than the stomodaeum.
g., the gonads situated on the lateral
ventral mesenteries.

the stomodaeum is provided with a broad groove armed with
very powerful cilia, by means of which the currents of water
in the canal system are maintained.

The bark or coenenchym of Corallium is of a dark- red
colour, due to the presence of a large number of red spicules
of calcium carbonate about -07 mm. in length (Fig. 50).
The spicules are formed by certain specialised cells in the
ectoderm covering the bark. These cells become detached
from the rest of the ectoderm and sink dow^n into the sub-
stance of the bark, where the spicules continue to grow,
until they become jammed together to form a solid mass of
coral. In this way the axis is formed and grows. The
increase in diameter of the axis of the stem and branches
does not seem to take place by the addition of newly formed
layers of jammed spicules, but continuously, so that in a

no CORALS

section of the coral growth rings are either absent or only
faintly indicated.

It is this continuit}' of the growth, together with the
completeness with which the spicules are jammed together
so as to leave no space between them, which gives to the
red coral its hardness, purity, and lustre when polished.
There are many other Alcyonaria in which the spicules
become pressed together in this way, but no others in w'hich
the amalgamation is so complete that their individual out-
lines and all intervening crevices and spaces between them
are entirely lost. It is difficult to give a general description
of the shape of the spicules in a few words, as they vary
enormously according to their age and
position. In the younger stages they
are usually oval or spindle-shaped, with
swollen, spiny extremities, and bearing
two circlets of four large spiny tubercles
on the body ; but as they increase in
size they seem to develop in a great
variety of ways. The spicules of some
other species of Corallium can be dis-
tinguished from those of the Medi-
FiG. 50.— Spicules of Cora/- terraucau Corallium iiohile bv their

liumnobile. >; 200 diams. ^■ ,< ^ >. 1 ~ i-

peculiar opera-glass shape, a modi-
fication of the type produced by an uneven development of
the two circles of tubercles ; but the spicules of all the
species are so variable that they never afford a very reliable
character for the systematic arrangement of the genus into
species.

The red coral of the Mediterranean Sea constitutes the
species Corallium nobile (Pallas) or C. rubrum, Lam. Of these
two names the former has undoubtedly the right of priority.

The same species extends into the Atlantic Ocean, and a
fishery of red coral on a smaller scale has been established
in the Cape Verde Islands and Madeira.

Other species of the same genus have been found off the
coasts of Japan, Timor, Djilolo, and Mauritius, and a few^
specimens in deep water off the west coast of Ireland, in the
Bav of Biscav, and other localities.

ALCYONARIAN CORALS iii

Until comparatively recent times there was a considerable
trade in red coral imported into Japan from Italy, because
the Daimyo of Tosa had prohibited the collection and sale
of the coral that was occasionally captured by the fishermen
in the Bay of Tosa ; but after the Meiji reform of 1868 a very
active industry sprang up, coral was found in other localities
than Tosa, where it was first discovered, and gradually the
exports of coral caught up and passed the imports. In 1901,
coral to the value of £50,000 was exported, and most of this
was sent to Italy, where the fishery was showing signs of
exhaustion.

The colour of these corals varies from white, ^ through
various shades of pink to red, and in some of the Japanese
varieties there is a yellowish tinge. The colour seems to be
very variable in all the shallow-water species. The deep-
sea forms from the Atlantic Ocean are usually white, but
the specimens of a species of Corallium obtained by the
Siboga Expedition, at a depth of 1089 metres, off Djilolo,
was of a full red colour. The variety called black coral, not
to be confounded with the "black " coral which is described on
pp. 244-250, is supposed to be due to some post-mortem change
in the organic constituent of the coral ; but a black specimen
obtained in the great depth of 1525 fathoms in the Atlantic
Ocean by the Challenger Expedition owed its colour to a
deposit of peroxide of manganese.

The attempt to group the specimens of this genus into
satisfactory specific groups is beset with difficulties. Both
colour and form seem to be so variable that they cannot
be relied upon as specific characters, and such differences as
are observed in the shape of the spicules and the degree of
retraction of the autozooids are difficult to express in precise
terms. So far as can be judged at present, however, the
Mediterranean red coral seems to be a distinct species. It
differs from all the other forms that have been examined in
two interesting peculiarities, (i) that the autozooids bear the
eggs and sperms and not the siphonozooids, and (2) that it is

1 White coral, although not so valuable as the red and pink varieties, is
now largely used in jewellery. It is cut from the stems of white species of
the genus Corallium, and is principally imported from Japan.

112

CORALS

vivipannis. It is possible also that it clifters trom the other
species in being sometimes hermaphrodite.

These are points, however, which are still in need of
further careful investigation.

TuBiPORA. — An Alc\-onarian coral that has a very wide

geographical distribution in
shallow tropical sea-water is
the well-known Organ-pipe
coral [Tiibipora musica). The
popular name was first given
to it by Tournefort in 1719,
and has reference to its con-
struction by a number of
cylindrical tubes arranged
almost parallel with one
another, and bound together
by a series of transverse
plates or platforms, so that,
viewed in section, there is
some resemblance to the
arrangement of the pipes of
a great organ (Fig. 51).

It is found alive, attached
to shells, corals, or stones, on
the reefs of many of the
shores of the Red Sea, Indian
Ocean, the tropical Pacific
Ocean, and the West Indies ;
and the dead corals are cast
up on to the beaches of some
of these shores in countless
numbers. When seen alive in a calm rock-pool, the familiar
form of the coral is hidden by a mantle of emerald-green
tentacles, but as the tide falls and the polyps contract, the
green colour fades away, exposing the ends of the red tubes
of which the skeleton structures are composed.

The Organ-pipe coral arises from a flat membranous
plate, which spreads over the surface of the substance to
which it is attached. From this plate of attachment or

i^— ^

Fig. 51. — Tiibipora niitsica. Apiece
of a large colony, showing the tubes
and the horizontal platforms from which
young tubes spring, P. One of the
tubes, T., has been dissected to show the
tabulae. Nat. size.

ALCYONARIAN CORALS 113

" stolon," as it is called, a number of tubes arise, which are
bound together by a horizontal platform at a distance of a
few millimetres from the base. Every tube passes through
the platform, and at a distance of another few millimetres
passes with its fellows through a second platform, and so on,
through several platforms, until the surface is reached.

If two or three of these primary tubes springing from the
base are traced through their whole length, it is found that
they are not quite parallel, but spread out fan-wise in all
directions, and from each of the platforms secondary tubes
arise which fill up the spaces between the primary tubes,
and thus in each series the number of tubes increases. By
this manner of growth great dome-shaped masses of coral
are formed which may reach the size of a man's head, but
the time comes when the weight of the mass is too great for
the support given by the few primary tubes that have
sprung from the stolon, and then it is broken off by wave
action, is rolled by the breakers, and eventually cast up on
the beach.

On making an anatomical examination of a preserved
specimen, it is found that the soft lining tissues of the polyps
do not extend below the level of the second platform from
the surface. The inner parts of the mass, therefore, are
nothing but a skeletal structure for the support of the living
surface ; but the shelter they afford attracts many interest-
ing examples of the aquatic fauna and flora, such as worms,
mollusca, crabs, and other Crustacea, encrusting sponges,
polyzoa and algae, so that it becomes a miniature museum
of strange creatures. Some of these organisms assist in the
destruction of the inner tubes, and thereby hasten the time
when the coral meets its fate by becoming detached from
its base.

The polyps are all of one kind, and have the typical
Alcyonarian structure. The mouth, at the distal extremity,
is surrounded by eight pinnate tentacles, and the short
throat or stomodaeum into which the mouth opens is con-
nected with the body wall by eight mesenteries.

\Mien the polyp is fully extended the body wall is con-
tinuous with the extremity of one of the red tubes. In

114 CORALS

contraction the tentacles are first folded inwards over the
mouth, and then the whole crown of tentacles, mouth, and
stomodaeum are drawn downwards into the tube, and this
is followed by the infolding of the body wall from above until
the limit of the red tube is reached. When the contraction
is complete the mouth of the tube is stoppered by the con-
tracted polyp, and thus the exit of the water from the body
cavity is prevented and the coral is able to retain its vitality,
even if the coral, by the fall of the tide, is left for a few hours
exposed to the tropical sun. The tubes are built up by the
growth and fusion of a large number of spicules of calcium
carbonate in the substance of the body wall. In the upper
part of the contractile part of the body wall the spicules
are small and scattered, in the lower part they are much
larger, and in the region of the junction of hard and soft
parts they have become so large that they are articulated
together to form a firm skeletal wall.

The firm coral substance or " corallum " of Tubipora is
constructed, therefore, in the same way as it is in Corallium,
by the fusion or, to be more correct, the jamming together
of Alcyonarian spicules. But whereas in Corallium the
substance thus formed is quite compact, in Tubipora a
number of spaces or pores are always left in the substance,
by which the living tissues can maintain a connexion
between the endoderm lining the inside of the tube and the
ectoderm covering the outside. The Organ-pipe coral is
therefore a perforate coral, and, like all perforate corals, its
substance is brittle, and is rapidly broken up and disin-
tegrated when exposed for any length of time to the action
of the surf. It is also a tabulate coral, but the tabulae
are very variable in form and frequently so different in
character from the tabulae of Millepora, Heliopora, and
many other corals that the name " tabula " does not seem
to be strictly applicable.

In some tubes there may be found a flat plate of coral
substance, dividing the cavity of the tube transversely on
the level of a platform. Such a plate is obviously a tabula
of the ordinary type. In other places the tabula is cup-
shaped, and more frequently it is drawn out into a fine point

ALCYONARIAN CORALS 115

in the direction of the platform next below it, and then it
may be called a funnel-shaped or " infundibuliform " tabula.

In many tubes, however, it is found that an infundibuli-
form tabula, instead of ending blindh^ expands again to
form an inverted funnel, the mouth of which is on a level
with the next platform. Thus we find within the tube an
inner tube, which contracts to a capillary size in the middle,
a structure which is obviously of the same nature, but
utterly unlike what is usually called a tabula in works on
corals. The interpretation of these different forms of
tabulae in Tubipora has been given elsewhere ; ^ but it is
important to note that the character of the tabulae varies
enormously, not only in the tubes of a single specimen, but
also in the different regions of a single tube, and it is there-
fore quite useless as a character for specific distinctions.

The genus Tubipora is one of the many genera of corals
in which the question of species is one of extraordinary
difficulty.

The lumps of this coral that are to be seen in museums in
this country differ from one another in shape, in the size of
the tubes, in the distance separating the platforms, and to
some extent in the shade of red colour of the coral substance.
All these characters, however, are so variable, so dependent
upon the characters of the environment in which the corals
grow, that any system of species founded upon them would
fail on account of an indefinite number of intermediate
varieties. On the shore of the Island of Celebes the author
took the opportunity' to collect and examine many hundreds
of specimens that had been washed up by the sea and many
scores of specimens alive on the coral reefs, and came to the
conclusion that almost every variety that is known could
be found on that one shore, and that there is complete
continuity between one extreme variety and another. This
does not entirely dispose of the question of specific grouping,
as other characters may yet be discovered which do not
exhibit the same degree of individual variability, but it

^ S. J. Hickson, Quart. Joitrn. Micr. Sci . xxiii., 1883. These curious
infundibuliform tabulae appear to ha\-e been first noticed by Ellis and
Solander, Zoophytes, Plate 27, 1786.

ii6 CORALS

leaves it in the position that at present only one species, of
almost world-wide distribution in shallow tropical waters,
can be recognised, and that species is Tuhipora miisica
Linnaeus, formerly called Tuhipora purpurea by Pallas and
Tournef.

The Organ-pipe coral was used in \'ery earh' times in
Egypt to make into little beads for ornament, but seems to
have fallen into disuse in all but the earliest dynasties.
Rumphius has some interesting notes on the magical pro-
perties attributed to it by the Malays of his time. It was
called the Batu swangi or Magicians' Stone, and was hung
on the trees to prevent thieves from stealing the fruit, for
anv thief who stole fruit from a tree that it protected became
affected with a rash of red pimples. It was also used in the
form of a powder as a medicine to cure strangury.

Telesto Rubra. — A brief note mav be added here on a
rare little coral of which only a few fragments have been
found in 20-40 fathoms of water off the islands of the Indian
Ocean. The colony consists of a single upright tube, re-
presenting the body wall of a long axial polyp, which bears
a few lateral branches of the same nature. The main stem
and the long tubes which spring from it bear a number of
prominent verrucae representing an equal number of lateral
or secondary polyps.

In the method of colony formation this species agrees
with the other species of the genus Telesto, but it differs
from all the others in the fact that the spicules coalesce as
they do in the genus Tubipora to form a compact but
profusely perforated calcareous tube of a pink or pale red
colour.

Small dried specimens of Telesto rubra might possibly
be mistaken for isolated tubes of Tubipora, although they
differ from that genus in the absence of anything correspond-
ing with the horizontal platforms and in the way in which
the young polyps are situated on the body wall of the old one.
Moreover, in T. rubra there are eight shallow longitudinal
ridges on the outside of the tubes, whereas in Tubipora the
tubes are always perfectly smooth.

The largest specimens that have been found are only

ALCYONARIAN CORALS 117

70 mm. in height, and the tubes have a diameter of
2-3 mm.

The only known locahties are Maldive Islands, 23-35
fathoms ; Trincomalee, Rutland Island, 35 fathoms ; and
Andaman Islands in 45 fathoms.

Paragorgia. — In the deep waters of the Norwegian
fjords there is found a large red branching Alcyonarian,
which might be mistaken at first sight for a coarse over-
grown precious coral ; but an examination of one of the
broken branches shows that it differs from Corallium in
having no hard and imperforate axis, the substance of the
branch right down to the centre being perforated by
numerous canals.

This is the Paragorgia arhorea or " Sea-cork tree " of
the older writers, and it probably received its specific name
because in magnitude it is better compared with a tree than
with any other kind of vegetable growth.

It is impossible to say to what size it may attain in
these great depths of water, far beyond the range of our
vision, as it is so brittle that with the best methods at our
disposal great difficulty has been found in bringing safely
to the surface complete specimens. But from rough calcula-
tions based on a circumference of five or six inches of some
of the large stems or branches that have been obtained it
is probably no exaggeration to say that the height from the
ground of some specimens must be over six feet.

In general anatomy the Paragorgia has many features
in common with Corallium, but it is much more vascular, and
the spicules never become so firmly interlocked and fused
together as to form a hard stony skeletal structure.

The substance of a dried specimen is light and porous,
and unless it is carefully handled is liable to break up into
fragments.

The species has a remarkable distribution. It is common
in the Norwegian fjords and extends North to the seas off
Nova Zembla and Franz Josef Land. It has not been
found in the British area nor off the Faroes and Iceland,
but turns up again in cold deep waters off the western side
of the North Atlantic. The most interesting feature of its

ii8 CORALS

distribution, however, is that the same species occurs in
deep water in the fjords of British ("ohunbia and a closely
allied species off the coast of Japan.

So far as our knowledge of its distribution goes, there-
fore, it seems to be a species confined to the cold deep
waters of the Northern Hemispheres with two remarkable
breaks in its continuity, one in the North Atlantic and the
other the American continent. It affords, therefore, an
interesting problem for students of geographical distribution.

Heliopora. — It was formerly supposed that Heliopora
was a Zoantharian coral until Moseley, during the voyage of
the Challenger Expedition, examined the polyps of some
specimens at Samboangan and proved that they have all
the essential characters of the Alcyonaria. But although
it is an Alcyonarian it occupies a unique and isolated
position in that Order on account of its massive corallum
of crystalline calcium carbonate, by the absence of the
characteristic Alcyonarian spicules, and by other structural
peculiarities.

There is one character which distinguishes the corallum of
Heliopora from all others, and that is the blue colour which
gives it its specific name. There is no other coral belonging
to any group that possesses this colour, and in every specimen
of Heliopora that has been examined the colour either per-
meates the whole corallum or can be seen just below the
surface in a fractured branch. On this account it has
received the popular name of " The Blue coral."

The form of the colony is very variable. It may be
branched like a stag's horn Madrepore, laminate, or almost
massive, but the ends of the branches are usually blunt and
lobed. It sometimes reaches a size of three or four feet in
diameter by two feet or more in height.

The surface of the corallum is rough and is perforated
by two kinds of pores, which may be called the large pores
and the small pores respectively, the small pores being very
much more numerous than the large ones. On looking
down into a large pore with a magnifying glass, a variable
number of shallow ridges may be seen projecting into the
lumen, which have a certain resemblance to the septa of

ALCYONARIAN CORALS

119

the Madreporarian corals, and are usually called the pseudo-
septa (Fig. 52).

On making a section of a branch the pores can be seen
to pass down into a series of parallel tubes with imperforate
walls, which are divided into chambers by numerous tabulae

(Fig. 53)-

The corallum of Heliopora is therefore imperforate,

tabulate, and dimorphic.

The structure of the soft parts of Heliopora is very
peculiar. It might have
been expected from the
characters of the corallum
that the polyps would
prove to be dimorphic,
and that we should find
in the large pores auto-
zooids and in the small
pores siphonozooids. But
this is not the case. In
the large pores there are
autozooids having the
general characters of
typical Alcyonarian
polyps, but in the smaller
pores there are only
tubular diverticula of the
canal system crowded
with zooxanthellae and
showing no trace of polyp

structures. It has been suggested that these tubular
cavities represent the body cavities of siphonozooids which
have been lost by degeneration ; but there is no evidence
to support that view.

When the Hehopora is seen alive on the reef, tlie polyps
are usually tightly x"etracted into the larger pores, but pro-
jecting from the grey surface a number of small thread-like
worms display their active contortionate movements. These
worms, belonging to the Polychaet genus Leucodora, are
very frequently associated with Heliopora, and the thin

l'"iG. 52. — Heliopora coerulea. A part of
the corallum highly magnified showing the
large pores with their false septa and the
small pores. Penetrating the surface are
seen five smooth cylindrical tubes of the
worm Leucodora.

120 CORALS

calcareous tubes which thev secrete may perforate the
corallum in all directions (see Figs. 51 and 52), and are so
numerous that they might be mistaken for a character of
the coral. Specimens of Heliopora from the Maldive Archi-
pelago are said to be free from this worm associate.

There is no record at present of the colour and appear-
ance of the expanded polyps of Heliopora, and observations
that have been made at low tide in the day time suggest
that they are never expanded in such conditions. It is
probable that like many other polyps they only expand at
night.

Heliopora is a curiously isolated genus in the system of
the Alcyonaria. It is the only recent genus of the Order
Coenothecalia to which it belongs. It has no near relations
among the Alcyonaria of the present day, but if we judge
from the character of its skeletal structures, it may be closely
related to a number of corals {e.g. Heliolites, Polytremacis,
etc.) which, in the early history of the world, flourished on
the reefs, but have long since become extinct.

Heliopora itself can be traced back through the Eocene
to the Cretaceous period, but Heliolites and many allied
genera died out before the close of the Palaeozoic period,
and Polytremacis and others survived only to early Tertiary
times. Heliopora is therefore the only survivor of a long
line of ancestors with a pedigree extending back to the
earliest times of which we have any record of corals, and so
far as we can judge from its abundance on some reefs and
the massive size it attains shows no signs of following its
ancestors to extinction.

The survival of Heliopora is a matter of special interest,
because most of the common corals of modern reefs, such as
Tubipora, Millepora, Madrepora, and Porites, are of com-
paratively recent origin.

Isis. — The coral that was called by the older writers the
King Coral is the first of the few examples we shall consider
in this chapter of the Polypiers coralligenes flexihles of
Lamouroux. In general structure it presents similar features
to those of Corallium. There is a hard axis covered by a
thick coenenchym bearing the polyps, but in Isis the polyps

Fig. 53. — Hdiopora coeritlea. A vertical section of a part of the corallum showing
the large pores P with their tabulae and numerous smaller pores between them.
At W the corallum is pierced by a worm tube, x 10 diams.

ALCYONARIAN CORALS

121

are all of one kind, similar to the autozooids of Corallium,
and the axis consists of alternate horny nodes and calcareous
internodes (Fig. 54).

This constitution of the axis renders the coral and its
branches capable of bending in any direction without break-
ing, and is in striking contrast to the
axis of Corallium, which is perfectly
rigid and can only resist the force of
the sea tides by virtue of its solidity
and strength.

There is a passage in the book on
Zoophytes by Ellis ^ which is worth
quoting here as it expresses remarkably
well the meaning of this structure of
the axis of Isis. " These joints are an
admirable contrivance of Nature to
secure the little branches of these
animals from being torn to pieces.
Without this they could not arrive to
the height of which some of them are
found, viz., of two or three feet, for
by bending freely to and fro with these
soft joints they easily resist the violent
motions of the sea."

The colony of an Isis is usually
branched in one plane forming a fan-
shaped coral, but specimens are some-
times found in which the ramification
is less regular and an aggregated mass
of irregular branches is the result. The
terminal branches are thick and end
bluntly.

The calcareous internodes of the main stem may be as
much as 10 mm. in length and 10 mm. in diameter and deli-
catelv fluted with grooves in which the nutritive canals
of the coenenchym lie. The horny nodes, which shrink and
become brittle when dry, are about 3-4 mm. in thickness.

Among the manv genera which are included in the family

^ The Xatitval History of Zoophvtes, by John Ellis, 1786, p. 103.

Fig. 54. — Isis hippuns.
The axis of one of the
terminal branches of a
large colony showing the
horny nodes and cal-
careous internodes. Xat.
size.

122

CORALS

Isidae, to which Isis belongs, there are various modes of
ramification, and it is important to note, therefore, that
Isis is one of those in which the branches always arise from
the calcareous internodes. The species with which we are
most familiar is called Isis hippuris. It is found in many
shallow-water localities in the W. Indies and in the Pacific

and Indian Oceans. It
was well known to
Rumphius,^ who says
that it was valued by
the natives of x\mboyna
and the neighbouring
islands as an antidote
against dysentery,
cholera, and other dis-
eases. Pallas states on
the authority of Im-
perato that Isis hippuris
occurs in the Mediter-
ranean Sea, but there
appears to be no recent
record of its occurrence
either north or south of
tropical waters,-

IsiDELLA. — Belong-
ing to the same family
as Isis, a much more
delicate coral called
Isidella is found in the
Mediterranean Sea, in
deep water in the fjords of Norway, and in the Bay of
Biscay.

In this form the ramification is more diffuse and usually
dichotomous, and the branches arise from the horn}' nodes
and not from the calcareous internodes as they do in Isis.
The internodes are long, slender, and smooth ; the nodes are

Fig.

-Isidella ncapiilitana. Xat. size.

1 The Accarbaar puti of the Malays (see p. 247).

- For a further account of this species see J. J. Simpson, Jotini. Liiiii.
Society, x.x.xvii., 1906.

ALCYONARIAN CORALS

12^

very short. The coenenchym covering the branches is very
thin (Fig. 55).

There is a passage in Phn^^'s Natural History, viii. cap.
52, which has given rise to some controversy. It may be
translated, " Juba states that
about the islands of the Troglo-
dytes there is a shrub found out
at sea called the ' Hair of Isis.' "
It is very unlikely that such a
name would have been given to
the coral now called Isis hippuris ;
but it may have been given to the
beautiful and delicate Isidella from
the Mediterranean Sea in the first
instance, and the same name given
at a later period to Isis liippiiris
on account of its similarly jointed
axis.

Melitodes. — In many regions
of the tropical seas there may be
found some very brightly coloured
flexible corals which might, at first
sight, be attributed to the family
Isidae, as they also exhibit a " con-
trivance " of alternate nodes and
internodes in the axis. Many of
these belong to the genus Melitodes.
A critical examination of the axis
shows that it is quite differently
constructed from the axis of Isis,
for, instead of being solid, both
nodes and internodes are perforated
by canals, and for this reason the

genus and its allies are placed in a separate family — the
Melitodidae. The largest and probably the commonest of
these is the species Melitodes ochracea, known to the older
writers as the Red King Coral.

The colour is very variable, as it is in all the species of
the genus, and may be either uniformly dark red or dark

Fig. 56. — Wnghtdla robitsta
from Singapore. The genus
Wrightella is closely related to
;\Ielitodes. Nat. size. After
Shann, Proc. Zool. Soc, 1912,
PI. LXII.

124 CORALS

red and chrome yellow, the two colours being variously
disposed.

When dried the coral is very brittle, so that it is difficult
to obtain a perfect specimen for a museum, but it is known
that the species may attain to a height of 3 feet and liave
a main stem half an inch or more in diameter.

On the reefs and in shallow water of the Indian Ocean
a dwarf species, Melitodes variabilis, is found which exhibits
very remarkable variation in the colour schemes. For
example, on one reef in an atoll of the Maldive Archipelago
the nodes were all red, but the internodes were grey or red
or pale yellow or salmon coloured. From other localities
in the same archipelago specimens were found with yellow
nodes and red internodes, with grey nodes and grey inter-
nodes, with red nodes and orange internodes, and many other
variations.

The Alcyonarian flexible corals with an unjointed axis
present such a great variety of form and minute structure
that they are now divided up by the systematists into a verv
large number of genera and species. To attempt to describe
the characters by which even the genera are distinguished
from one another so as to give the reader a guide to the
determination of the generic names would be a task that
would take far more space than can be allotted to this
group of corals. A few well-known genera have been
selected, therefore, w^hich will illustrate some of the more
important characters of the families they represent.

The word Gorgonia as applied to flexible corals of some
kinds is of very ancient origin and may have been derived
from the Gorgones, the mythical ladies whose hair was
said to be entwined with serpents ; but it is quite impossible
to determine whether the classical writers applied the name
to any one kind of flexible coral or to any kind of marine
product having a black horny axis. The same sort of
errors and myths gathered round the Gorgonians as round
the red coral, and it is evident that the}'- were regarded as of
the same nature as Corallium.

Pliny ^ says " Gorgonia nihil aliud est quam curalium ;

1 xxxv'ii. 10. 164.

ALCYONARIAN CORALS 125

nominis causa, quod in duritiam lapidis mutatur emollitum
in mari ; banc fascinationibus resistere adiirmant."

Such a definition of a coral which asserts that it is soft
in the water and turns hard on exposure to the air, and that
it has the power of resisting fascinations, may not be satis-
factory to the modern zoologist, but it, at least, lends support
to the view that the Romans regarded the Gorgonians as
something of the same nature as corals.

At the present day the generic name Gorgonia is very
much more restricted than it was even at the beginning of
the last century, and a host of new generic names have been
invented for many of the Gorgonians of the old writers.
These genera are divided into six families, of which four —
the Gorgoniidae, Gorgonellidae, Plexauridae, and Prim-
noidae — are usually represented in museums by typical
specimens.

There are three principal characters distinguishing the
Gorgoniidae from the other five families. The axis is horny
without any admixture of calcareous matter, the coenen-
chym is thin, and the polyps are retractile.

The axis is variously but usually profusely and delicately
ramified, and in dried and retracted specimens the position
of the zooids is represented by more or less prominent
mounds or verrucae on the coenenchym.

Gorgonia. — One of the most familiar of the Gorgoniidae
is the Gorgonia flahellmn'^ of the shallow waters of the
West Indies and other localities of the tropical Atlantic,
which forms delicate fan-shaped structures by the profuse
anastomosing of slender branches arranged in one plane.

Other genera of Gorgoniidae, such as Leptogorgia and
Pterogorgia, form immense tufts or shrubs ending in long
delicate branches which bend in all directions with the
movements of the water, like grass in the wind, and with
their brilliant purple, yellow, and red colours contribute to
the brilliancy of the pools of the coral reefs in which they
are often found. These beautiful and variously coloured
corals form an effective display in a museum case.

In some respects, however, the most interesting member

^ Rhipidogorgia.

126 CORALS

of the family is Gorgonia verrucosa, the only representative
of its kind in the British area, and being common in the
Mediterranean Sea was probably one of the first of the Order
to be given the name Gorgonia. Unfortunately systematic
controversy has raged round this common species, and it
has been shifted about from one genus to another and
from one family to another according to the weight attached
to particular characters by different writers.

The view that will be accepted in this book is that its
proper generic name is Gorgonia and that its proper family
is the Gorgoniidae, but it should be stated that some
authorities consider that it should be called Eunicella and
given a place in the family Plexauridae.^

The controversy in this case really turns on the question
whether the coenenchym should be described as thick or
thin. It is, as a matter of fact, thicker than it usually is
in the Gorgoniidae and thinner than it usually is in the
Plexauridae, and the species in this respect as in others is
intermediate in character between the families, but it may
be held that being in such a doubtful position it should be
classed with the Gorgoniidae on historical grounds.

Gorgonia verrucosa, sometimes called the Sea-fan (Fig.
57), is found in shallow water in the Mediterranean Sea and
on the coasts of Brittany, Devonshire, and Cornwall. It
grows to a height of a foot or more and, rising from a short
stalk attached to some foreign substance, begins to divide
up into branches almost at once to form an irregular fan-
shaped colony. In large specimens the main stem and some
of the larger branches are bare, the black horny axis being
exposed. On most of the larger branches, however, the
coenenchym is thin and transparent. On the finer and
terminal branches only is it relatively thick. From the
surface of the coenenchym there project a large number of
little mounds or verrucae about 3 mm. in diameter, crowded
together on the terminal branches but more scattered on
the larger ones. These verrucae shelter the thin trans-
parent polyps in the retracted condition. They are usually
irregularly distributed, but in some specimens in the Medi-

^ See J. S. Thomson, Ann. and Mag. Xat. Hist, x., 1912, 4S2.

ALCYONARIAN CORALS

127

terranean Sea (regarded by von Koch as a distinct species,
G. cavolini) they are arranged in longitudinal rows.

When alive and expanded the colonies are red, yellow,
or white, but the colours fade when the colony is dried or
preserved in spirit. Museum specimens are always white.

Fig.

-Gorgonia verrucosa. Part of a colony from Plymouth.

Gorgonia flammea. Among the many varieties of
Gorgoniidae that are usually found in our collections there
is one that calls for a few words on account of its great size
and ver}' conspicuous colour. This is the Gorgonia {Lopho-
gorgia) flammea, which is found in shallow water in Algoa
Bay and other localities off the coast of South Africa. It can

128 CORALS

be recognised at once by the fact that the stems and
branches are considerably flattened and by its brihiant
scarlet colour. Specimens over four feet in height have
been found.

In the West Indies the most conspicuous members of
the family are Leptogorgia, Pterogorgia, and Xiphigorgia,
which form great tufts of long flexible branches frequently
adorned with brilliant purple, red, and yellow colour. In
Leptogorgia and Pterogorgia the polyps are arranged
laterally on the branches, and between them in dried
specimens there is a shallow longitudinal groove. In
Pterogorgia the polyps when retracted are protected by
well-marked verrucae ; in Leptogorgia the verrucae are very
small and not raised above the level of the coenenchym.
In Xiphigorgia the position of the polyps is indicated in
dried specimens by three or four prominent ridges without
verruciform swellings.

The genus Phyllogorgia, also found in the West Indies,
is characterised by the leaf-like expansion of the branches of
its flabelliform colony.

The family Gorgonellidae includes a large number of
genera many of which have a close resemblance to the
Gorgoniidae. The coenenchym is usually thin and the posi-
tion of the retracted polyps indicated by low mounds or
verrucae. The only constant difference between the two
families is that the horny axis is impregnated with calcareous
matter.

To determine therefore whether a given specimen is a
Gorgoniid or a Gorgonellid the first test is to place a piece
of the axis, thoroughly well cleaned of its coenenchym, in
nitric or hydrochloric acid. If it is a Gorgonellid it will
give off bubbles of carbon dioxide, and if it is a Gorgonud
it will not.

JuxcELLA. — One of the most interesting of the Gor-
gonellids is Juncella, in which the long brown cylindrical
axis is usuallv unbranched and sometimes has a length of
several feet and is as thick as a finger. When fresh the axis
is covered with a red or orange coloured coenenchym of

ALCYONARIAN CORALS 129

medium thickness and may be smooth or covered with
numerous irregularly arranged verrucae.

Juncella has received various popular names such as
Sea-rope, Sea-stalk, Sea-whip, and when stripped of its
coenenchym it is used by the natives of the tropical
countries in which it is found as a walking-stick and for
other purposes, but it does not seem to have been used
in the time of Rumphius by the Malays for medical pur-
poses, as were so many of the other flexible corals.

Another very interesting family of these corals is the
Primnoidae, in which the polyps are not retractile into the
coenenchym and are protected by an elaborate mail of
overlapping calcareous scales. The axis is unjointed and
horny, but as with the Gorgonellidae the horny substance
is impregnated with calcium carbonate.

Primxoa. — Most of the genera and species of this
family live in deep water and are not very familiar
objects in museums, but there is one species, Primnoa
reseda, which is occasionally found in British waters
and may be taken as an example of its kind for a short
description.

There is a quaint description of this species in Parkinson's
Theatre of Plants (1640), p. 1301, where it is called Reseda
marina, or the Base wilde Rocket of the Sea : " Clusius in
his sixte booke of Exotickes and sixt Chapter saith he had
this at Amsterdam, and for the rarenesse, there set it forth
to be of a hard woody substance, crusted over with the
saltnesse of the Sea, being not the whole plant, but much
of the lower parts, broken away, yet containing sundry
branches, covered upwards, with sundry rough cups or
vessels, hanging downewards, of a whitish ash colour, not
much unlike unto the seed vessels of Reseda when they are
ripe, but much lesse, and so brittle that they might be
rubbed to pouther between the fingers."

From this account it will be seen that the popular
English name for it, the Sea-mignonette, is one of long
standing.

The branching of the colony of this species is irregularly

130

CORALS

(lichotomous and the branches are arranged more or less in
one plane (Fig. 58).

A very fine specimen obtained by the GoLiseeker ^ at
a depth of 183 fathoms in the Faroe Channel was nearly

three feet in height with a
spread of fourteen inches.
But this specimen was ex-
ceptionally large.

The polyps are about
5 mm. in length, arranged
densely and quite irregularly
on a thin coenenchym,
slightly curved and, as
observed b\' Clusius, bent
downwards. The polyps are
protected by a number of
large overlapping calcareous
scales, and the disc and
retracted tentacles are
covered by eight smaller
opercular scales (Fig. 59).
There is no record of any of
these polyps having been
observed fully expanded, so
that we have no knowledge
of their appearance except
in the retracted and some-
what contracted condition
in which they are seen when
they are brought on deck
from the depths of the sea.

One of the most note-
worthy features of Primnoa
reseda is the brilliant salmon-pink colour it shows when fresh,
which perhaps justifies the enthusiastic comment that it is
" one of the most gorgeous animals within the British area."
The colour is, however, not permanent like the colours
referred to in other Alcyonaria, but dissolves in the pre-

^ See J. A. Thomson, Proc. Roy. Soc. Edm. xvii., 1906.

Fig. 58. — Primnoa reseda. A part of
a large specimen. On the left of the
photograph the bark has been scraped to
show the horny axis. Nat. size.

ALCYONARIAX CORALS

131

servatives or fades away if the coral is dried, and thus in
the collections it has the " whitish ash colour " that Clusius
describes.

Primnoa reseda is found in deep water in several localities
off the west coast of Scotland, the Shetland Islands, and the
Faroe Channel. It is also found in the Norwegian fjords and
in the Bay of Fundy on the North American coast. It does
not seem to occur in the Mediterranean Sea or in the Tropics.

There are man}^ genera and species
belonging to this family distinguished
from one another by the details of the
armature of the polyps and other char-
acters.^ The polyps are frequently ar-
ranged in regular whorls instead of
irregularly as they are in P. reseda, and
they frequently bend upwards, not down-
wards as they do in this species. Two
species in which the polyps are thus
arranged in whorls have been found in
deep water off the Irish coast. Specimens
of Caligorgia flabellum, a species with
whorls of small polyps which bend up-
wards, were obtained from 500 - 700
fathoms, and also a specimen of Siaclivodes
versluysii, about four feet in length and
unbranched, with whorls of large polyps
which bend downwards, in 500 fathoms."

Fig. 59. — Primnoa
reseda. A small part
of a branch showing
the polyps covered
with an armature of
scales. In this genus
the polyps hang down-
wards. • :: diams.

Members of the family Plexauridae, to
which reference must be made, differ
from the Gorgoniidae in having a thick coenenchym cover-
ing the axis, and the branches are consequently relatively
thick and coarse (Fig. 60).

The axis is sometimes purel}^ hornv, but occasionally
contains some calcareous granules, and at the swollen base
of attachment it is frequently so densely impregnated with
calcareous salts that it is as hard as limestone.

^ J. Versluys, Primnoidae of the Siboga Expedition, 1906.
- Jane Stephens, Fisheries, Ireland, Scientific Investigations, 1909, \'.

13^

CORALS

There is one more interesting feature about the Plex-
auridae which is very difficult to account for, and that is that
in dried specimens the coenench^-m is nearly always white.
The colonies rarely present any of those brilliant colours
which are seen in the Gorgoniidae and Gorgonellidae.

The old genus Plexaura has in recent years been split up
into a number of genera on the ground of differences in the
structure of spicules and in other characters which need not
concern us now, but the principal interest of this group of
genera is that the hard black axes are very largely used even
at the present day by the mariners of the Indian and Pacific

Fig. 6o. — Plexaura. A part of a specimen from Torres Straits. Note the
thickness of the bark as seen on some of the terminal branches where the horny
a.xis projects. About i nat. size.

Oceans to make into bracelets and other amulets as a pro-
tection against rheumatism and the dangers of the sea (see
p. 247). There can be little doubt that the Accarhaar itain
of the Malavs mentioned by Rumphius was a Plexaurid.

It is difficult to determine with any degree of certainty
what the stony rushes (junci) were that the soldiers of
Alexander observed in the Indian seas. They may have
been Gorgonians of various kinds or possibly Antipatharia,
but nothing fits the description better than some of the
species of the Plexauridae.

The last two families of these flexible corals do not

ALCYONARIAN CORALS 133

contain any genera that are very well known, and most
of them are to be considered among the rarities of museum
collections.

The Muriceidae is a very large and difficult family
showing great variety in form, colour, and habit. The
most noticeable character is that the surface of the coen-
enchym and of the polyps is usually armed with minute
spines, so that it is rough or harsh to the touch. This is
due to the fact that many of the spicules at the surface are
relatively large and provided with spines which project
through the ectoderm (Fig. 45 D, p. 105).

The Chrysogorgiidae are almost entirely confined to deep
water, and are very rare. In a large proportion of the
species the spicules are thin oval or hour-glass plates. This
character of the spicules has suggested to some authors
that the Chrysogorgiidae are the most primitive of all the
Gorgonacea, but it is possible that this and other characters
may be associated with the life in the slow uniform currents
of deep water, and a sign of special adaptation rather than
of primitive features.

Ceratoporella.^ — A very remarkable coral was obtained
by the naturalists of the American Blake Expedition in 100
fathoms of water off Cuba, the zoological position of which
was difficult to determine-.

The single unique specimen consists of a lump of very
hard limestone perforated by boring sponges in various
directions. Projecting from one side of this lump there is a
mushroom-shaped process capped by a thin brown lamina,
circular in outline and 42 mm. in diameter, composed of
short vertical tubes. There seems to be little doubt that
the whole lump of coral was formed by the successive growth
of the organisms that constructed the short brown tubes at
the surface (Figs. 61 and 62).

1 See Hickson on " Ceratopora," Proc. Roy. Soc, 191 1, vol. 84, p. 195.
The name Ceratopora, being preoccupied, was subsequently changed to
Ceratoporella.

134

CORALS

The tubes are not tabulate and show no signs of septa
or cohimella, and the coralhim is imperforate. They are
about 0-2 mm. in diameter and i mm. in length, ending
below in a conical pit in the solid calcareous substance.

Fig. 6i. — CcvatoporcUa nichohonii. Off Cuba, loo fathoms. Xat. size

The onlv evidence there is of the affinities of this coral is
afforded by the presence in the margin of the tubes of a
number of slender calcareous tuberculate spicules. These
spicules have a close resemblance to the spicules of some of
the Alcvonaria.

Fig. 62. — Surface view of Ceratoporella

10 diams.

It must not be considered as certain that Ceratoporella
is an Alcyonarian from this single piece of evidence, as
spicules of various kinds and sizes are also formed by cal-

ALCYONARIAN CORALS 135

careous sponges, but when it is combined with a system of
regular monomorphic tubes the balance of evidence turns
down the Alcyonarian side of the scale.

The examples of Alcyonaria described in the preceding
pages are not arranged in their zoological order, and the
following table is added to indicate to the student the system
of classification and the position of these examples in the
group.

(3rder I. — Stolonifera. Primary polyps springing in-
dependently from a membranous or ribbon-like axis.

Tubipora.
Telesto.

Order II. — Alcyonacea. Colonies without an axis,
spongy in texture.

Alcyonium.
Sarcophytum.

Order III. — Coenothecalia. Colonies without an axis,
stony in texture.

Heliopora.
Ceratoporella ?

Order IV. — Gorgonacea. Colonies with an axis.

Sub-order A. — Pseudaxonia. Axis perforated
by canals or solid and ston}'.
\\'rightella. Corallium.
Paragorgia. Melitodes.

Sub-order B. — Axifera. Axis solid, horny, or
horny and calcareous.
Gorgonia. Plexaura.
Isidella. Primnoa.
Isis. Pterogorgia.
Juncella. Rhipidogorgia.
Leptogorgia. Xiphigorgia.

CHAPTER \l

ANTIPATHARIAN CORALS

" La principale difference que Ton observe entre les Antipates et
les Gorgones, consiste dans la nature de I'ecorce ; ces dernieres
I'offrent plus ou moins cretacee, friable et presque terreuse par la
dessication, tandis que dans les premiers, elle est d'une consistance
presque semblable a une substance gommeuse dessechee." — ■
Lamouroux, Polypiers coralligeves flexibles, p. 368.

The group of the Antipatharia exhibits the same character
as that of the family Gorgoniidae of the Alcyonaria in form-
ing a hard, horny axial support which is not impregnated
with calcareous matter. The Antipatharia, like the flexible
Alcyonarian corals, also show a great variety in the form and
method of branching. Some have a long straight or spirally
twisted unbranched stem ; some branch in all directions like
a shrub, others in one plane to form a fan-shaped structure.
In some the branches anastomose to form a network, in
others they do not. It is not, therefore, possible to dis-
tinguish with certainty the axis of an Antipathes from the
axis of a Gorgoniid either by its chemical composition or by
its mode of growth.

The horny axis of the Antipatharian corals, however, can
usually be recognised when the finer terminal branches are
examined with a lens, because they are provided with a
number of sharp, thorn-like processes which give them a
rough or prickly surface (Fig. 64), and on this account they
were called by the older writers the Prickle corals (Stachel-
korallen). It is on the arrangement of these thorns on the
branches that the classification of the Antipatharia into
genera and species largely depends. The main stem and

136

ANTIPATHARIAN CORALS 137

the larger branches are frequently without thorns, and
present a hard, smooth, and often highly polished jet-black
surface. The axis of the Gorgoniidae and Plexauridae is
never provided with thorns, and although it may be grooved,
always feels smooth to the touch, and the same is true of
the genus Gerardia, which is described at the end of this
chapter.

In transverse sections of a stem or thick branch of an
Antipatharian coral there is usually found a central circular
cavitv around which the horny matter is arranged in a
number of concentric layers. It has, therefore, some re-
semblance to a section of a tree stem, the central cavity
corresponding with the pith and the concentric layers of
keratin with the annual rings of wood.

In the axis of the Gorgonacea there is usually no central
cavity, the texture is more fibrous than in the Antipatharia,
and the concentric lamellae, if present, much less well
defined.

In the large thick stems of the black coral some-
times used by the Japanese for making their elaborately
carved netsukes, the central cavity and the arrangement in
concentric layers may be entirely obscured, although this
coral is undoubtedly Antipatharian in origin, and conse-
quently no single character is left by which the exact
nature of black coral can be determined with certainty.

The soft living tissue which covers and secretes the horny
axis of the Antipatharia is absolutely different from that of
any of the Alcyonarian flexible corals. It forms only a thin
white or purple coloured transparent film, and is entirely
devoid of spicules or any other kind of calcareous structures.
This character of the soft tissues of the Antipatharia was
recognised by Rumphius, Pallas, and other writers of the
eighteenth and early part of the nineteenth centuries.^ They
called it slime or mucus in contrast to the coenenchym of
the Alcyonaria, which they called " bark."

The polyps are small, and, with a few exceptions, are

^ " Cortex autem, quo Antipathes vivit, non calcareus est ; sed
gelatinosum tegumentum in extremis ramis crassius, inque polypos efflor-
escens " (P. S. Pallas, Elenchus Zoophytoruni, 1766, p. 206).

138 CORALS

provided with only six short hnger-shapcd tentacles and
six complete mesenteries (Fig. 63).

Provided, therefore, that some of these soft tissues are
preserved, there is no difficulty whatever in distinguishing
an Antipathes from a Gorgonia, but unfortunately they
entirely disappear when the coral is dried, and all that
usually finds its way into the hands of the collector is the
bare horny axis. The axis of the stems and larger branches
of Antipatharia were undoubtedly one of the sources of the
black coral of ancient writers, which was used, as is related
in another chapter, for its power of " resisting fascinations " ;
but it must be said that, in all probability, the Greek word
Antipathes, which literally means an Antidote, was also

Fig. 63. — Antipallu's larix. A small part of a branch showing three polyps
each with six tentacles. x 20 diams.

apphed to other horny axes than those of the corals we
now call Antipatharia.

The classification of the Antipatharia into families and
genera has proved to be a matter of great difiiculty, because
the characters afforded by the axis alone are very unreliable,
and the characters afforded by the soft parts are but rarely
sufficiently well preserved to be trustworthy.^ It is, there-
fore, a task which requires not only a great knowledge of
the literature, but also skill and experience to determine
with any certainty to what genus or species a given
specimen belongs. This is a task which as a rule must be
left to the specialist.

1 For an excellent and thorough survey of the group the monograph
by A. J. van Pesch, The Antipatharia of the Siboga Expedition, Livr. Ixxiii.,
1914, should be consulted.

ANTIPATHARIAN CORALS 139

To illustrate the general character of the group, reference
may be made to two or three forms in which the task of
identification is a comparatively simple one.

Antipathcs (Parantipathes) lan'x is a species which has
been found in deep water in the Mediterranean Sea, off the
Faroe Islands, off the west coast of Ireland, in the Bay of
Biscay, and also in the Sulu Sea in the Malay Archipelago.

It has a very characteristic method of branching, which
has been compared with a twig of a larch tree but is more
expressively termed " bottle-brush form."

In many specimens there is a central main unbranched
stem attached to a stone from which spring five or six
longitudinal rows of numerous long delicate branches,
usually called the pinnules. The pinnules stand out at
right angles to the main stem, and as they are of approxi-

P"iG. 64. — Autipathi's lari.x. A part ot the horny axis of a branch showing the
characteristic rows of thorns. 20 diaras.

mately equal length they have the same kind of appearance
as the bristles on a bottle-brush.

The polyps are arranged in a single row on the upper
side of these pinnules, and it is not difficult to see in well-
preserved specimens from Naples (Fig. 63) that each polyp
possesses six tentacles, and that each tentacle bears a
number of dome-shaped tubercles which are armed with
stinging cells (nematocysts). There is, strictly speaking, no
coenenchym, as the row of polyps is continuous, and each
polyp communicates directly with its neighbours.

Unbranched specimens over one foot in height were
found in 412 fathoms of water by the Huxley Expedition in
the Bay of Biscay,^ and a fine specimen, over three feet in
height, with more than half a dozen strong branches bearing
the pinnules, has been described by Professor Thomson ^
from the Faroes.

^ S. J. Hickson, Journ. Mar. Biol. Assoc, viii., 1907.
^ J. A. Thomson, Proc. Roy. Soc. Edin. xvii. 5, 1908.

140 CORALS

Antipathes spiralis of the older authors is characterised
by the single unbranched stem, which is twisted in a spiral
fashion.

This is the Palmijuncus anguiniis of Rumphius, and
seems to have, like many other Antipatharia, a world-wide
distribution. It might be mistaken for the stripped axis of
one of the Juncellidae (see p. 128), but differs from it in the
presence of prickles on the surface and by the absence of any
calcareous matter in its composition.

Unbranched spiral specimens of Antipathes are now
relegated to two different genera, Cirripathes and Sticho-
pathes, which differ from one another in the arrangement of
the polyps In the former they are situated in several rows
on the stem, in the latter in a single row.

Rumphius states that specimens over five feet in length
were obtained in the Amboyna vSea, but specimens of
Stichopathes spiralis taken in deep water in the Bav of
Biscay and of Cirripathes spiralis taken off the west coast of
Ireland are not more than one foot in length.

In the third form of growth, which may be described
under the name Antipathes flahellmn (Fig. 65), there is a
short thick stem attached to a rock. This stem breaks up
immediately into a profusion of small branches arranged in
one plane, which divide and subdivide and anastomose to
form a fan-shaped structure. In old times these corals
were called " mourning fans " (Trauerfacher) to distinguish
them from the Gorgonacean sea-fans.

In the modern system of nomenclature the fan-shaped
Antipatharia are relegated to two or more genera (Aphani-
pathes, Tylopathes).

There are several other genera with a more irregular
method of branching, but they are difficult to distinguish
from one another without special study of the polyps and
the arrangement of the prickles on the terminal branches.
For the identification of these the recent memoirs on the
group should be consulted.

/^^^-^^

Fig. 65. — Aiitipathcs {Tylopatlics) JJabellum. f nat. size.

ANTIPATHARIAN CORALS 141

ZOANTHIDEAN CORALS

Gerardia savalia is the accepted name for a remarkable
Mediterranean black coral which was first mentioned by
Ferrante Imperato in 1599 under the name Savaglia.

From the fact that it has a black horny axis it was, until
recent times, classified with the Antipatharia, but the
researches of Carlgren ^ have shown that the polyps which
form the axis of Gerardia have a different structure from the
Antipatharian polyps, and resemble in essential characters
those of another group of Coelenterata called the Zoanthidea.
It is not necessary to give full details of the structure of these
polyps, but it may be said that they have a great many
more tentacles (twenty-four or more) and mesenteries than
the polyps of the Antipatharia, and that when retracted
they form a thicker bark or crust over the axis.

The colony is said to begin life by encrusting a stem of
a Gorgonia, but soon surpassing its support in growth it
forms a basal horny skeleton of its own and builds up very
large branching colonies.

Many authors refer to the great size which specimens of
this coral reach, and it is possible that Gerardia was the
principal source of the black coral that was used by the
Mediterranean races in early times.

A specimen, now in the British Museum, that was
dredged up from a depth of 20 fathoms of water off the
Grecian island of Negropont, is 6| feet in height and has
an expanse of 6 feet 8 inches. The main trunk from
which the branches arise is i foot 5 inches in circumference.^

The anatomy of Gerardia was first described by de Lacaze-
Duthiers,^ who gave some beautiful illustrations of the
anemone-like polyps when fully expanded. The colour of
the polyps is said to be normally a greenish-yellow, but at
the time when they are charged with reproductive bodies
this colour, as well as the usual transparency of the tissues,
may be obscured by the brick-red eggs or the white testes.

1 Carlgren, Ofvers K. vet. Akad., 1895, 5.

- F. J. Bell, Trans. Zool. Soc, London, 1891, p. 87.

^ De Lacaze-Duthiers, Ann. Sci. Nat. (5), ii., 1861, p. 169.

142 CORALS

The axis of Gerardia consists of a series of concentric
lamellae of black horny substance, but the lamellae appear
to be more firmly cemented together than is generally the
case in the Antipatharia. In the centre of the axis there is
usually found a core of a substance which is not formed by
the Gerardia. This may be the stem of a Gorgonian coral
or some other structure which the (ierardia has covered by
encrustation in the early stages of its growth.

The surface of the axis is smooth to the touch, as it
does not possess the prickles or spines which form such a
characteristic feature of the axis of the branches of the
Antipatharia. But when the surface is examined with a
magnifying glass it is found to be covered with a number
of little pitted mounds {mamelons omhiliqiies)}

So far as is known at present the genus Gerardia is
confined to the Mediterranean Sea. The large specimen in
the British Museum came from Grecian waters, but speci-
mens of great size are also obtained by the coral fishers on
the coast of Algeria and Tunis.

1 According to de Lacaze-Duthiers, I.e. p. 216.

CHAPTER \TI

HYDROZOAX CORALS

" When a Writer acquaints me only with his Thoughts and Con-
jectures, without enriching his Discourse with any real Experiment
or Observation, if he be mistaken in his Ratiocination, I am in
some Danger of erring with him, or at least am like to lose my
Time, without receiving any valuable Compensation for so great a
Loss ; but if a Writer endeavours by delivering new and real
Observations and Experiments to credit his Opinions, the Case is
much otherwise : for let his Opinions be ever so false I am not
obliged to believe the former, and am left at Liberty to benefit
mvself bv the latter ; and though he have erroneously superstructed
upon his Experiments, yet, the Foundation being solid, a more wary
Builder may be much farthered by it, in the Erection of a more
judicious and consistent fabrick." — Mr. Boyle, quoted by H. Baker,
I.e. p. 206.

The polyps of the Hydrozoa, although presenting an ex-
ternal appearance very similar to that of the polyps of the
other Coelenterata, are much simpler in structure.

There is normally a mouth surrounded by a crown of
tentacles varying in number in the different genera of the
group, but always filiform or digitiform in shape and without
lateral pinnules, but the mouth leads directly into the body
cavity and there is no stomodaeum and no mesenteries.

Most of the genera of Hydrozoa form colonies by gemma-
tion, which are attached to the rocks or sand by root-like
processes, and, by various methods of ramification, give rise
to plant-like structures of considerable size.

By the older naturalists they were included in that
strange medley of marine products called the Zoophytes.

Before passing on to the description of the Hydrozoa
that form calcareous structures there are two morphological

143

144 CORALS

features of the group to which a passing reference must be
made.

In many of the colonies it is found that the polyps
are not all alike but present two or more different kinds
adapted for different purposes. One of the commonest
forms of this dimorphism is seen in the two Orders of
Hydrozoan corals which will be described in this chapter.
It consists in the reduction of the tentacles of the one kind,
called the gasterozooids, so that they become httle more than
a mouth and digestive tube, and in the loss of the mouth and
digestive functions in the other kind, called the dactylo-
zooids, which become elongated, flexible, and active for
catching food by means of the numerous batteries of
nematocysts with which they are armed.

The second feature of importance concerns the origin
and position of the ovaries and testes. These organs are
always situated in the outer layer of the body wall, and
their products when ripe are always discharged directly
into the sea and never pass through the body cavity as they
do in the Orders of Coelenterata that have been described
in previous chapters. Sometimes these genital organs are
found on the body wall of ordinary Hydrozoan polyps, but
in many other cases they are only borne by specially modified
zooids called the medusae, which become detached from the
parent colony and swim away to distribute their sexual
products in the open sea.

The medusae are little jelly-fish having a very different
appearance from the sedentary polyps of the colony. They
have the form of minute umbrellas with usually a ring of
tentacles round the margin, and for a handle a short process
called the manubrium, at the end of which is situated the
mouth.

In some cases the medusa undergoes degeneration, losing
its principal characters, and never succeeds in becoming
detached from the parent colony. The story of this
degeneration is one of extreme interest to the zoologist, but
it has no bearing on the problems dealt with in this book.

There are two Orders of the Hydrozoa that may fairly
be called Corals. These are the Milleporina and the Styla-

HYDROZOAN CORALS 145

sterina. In many text-books of zoology they are still grouped
together to form the Order Hydrocorallinae, but although
they have in common the two characters of dimorphism and
a massive calcareous corallum, the structure of the polyps
and of the reproductive bodies suggest that the resemblances
between the two groups are due to convergence rather than
to genetic affinity.

The Order Milleporina is constituted for only one genus
— Millepora — which has a wide distribution in the warm
shallow waters of the East and West Indies. It was A.
Agassiz in 1859 who first proved that the correct position
of the genus is in the class Hydrozoa, but Moseley's brilliant
researches during the voyage of H.M.S. Challenger in 1876 ^
provided us with the first correct account of its general
structure.

The corallum assumes many varieties of form. Some-
times it consists of thick massive plates, sometimes it is
coarsely branched or becomes profusely ramified. These
differences in form seem to be associated with differences
in the conditions of the immediate environment and cannot
be used as characters for specific distinctions.

The special characters of the corallum can be easily
recognised with the help of a simple magnifying glass. The
surface is perforated by a very large number of pores, and
these pores are of two sizes, the larger or gasteropore
(about 0-25 mm. in diameter) and the smaller or dactylo-
pores (about 0-15 mm. in diameter) (Fig. 66).

When examined in sections these pores are seen to lead
into delicate tubes which pass radially towards the centre
of the branch, and each tube is divided into a number of
chambers by very thin transverse partitions called the
tabulae (Fig. 67, Tab.). Between the tubes the corallum is
seen to be perforated by a dense plexus of branching canals.
On account of its porous texture Millepora was named by
Rumphius Lithodendriim saccharacemn album, or the White
Sugar Coral.

The corallum is therefore perforate, tabulate, and pro-
vided with dimorphic pores.

^ H. N. Moseley, Challenger Reports, vol. ii., 1881.

146 CORALS

In many specimens, and particularly in the older parts
of the corallum, the pores are arranged in circles — called the
cyclo-systems — a single gasteropore in the centre of the
circle and a ring of five to seven dactylopores around it. x^t
the growing edges of the fronds or branches and all over the
surface of some specimens the pores seem to be much more
irregularly scattered. The arrangement of the pores in
cyclo-systems must not, therefore, be regarded as an in-

FiG. 66. — Millcpora. A part of a frond of a large colony, showing the spores
arranged in regular cyclo-systems. Xat. size.

variable character of the corallum of Millepora. Occasion-
ally there may be found in museum collections specimens
of the coralla of Millepora which look as if they were afflicted
with a disease or were otherwise abnormal (Fig. 68). They
exhibit all over the surface, or on some parts of it only, a
number of shallow, blister-like cups having a diameter about
twice that of the gasteropores. These cups are the Am-
pullae, and it is now known that they are the receptacles
of the medusae which bear the eggs or sperms.^ They are

1 S. J. Hickson, Proc. Roy. Soc, vol. l.xvi., 1899.

^ Med

Can 2

Fig. 67. — Diagram of a living Millepora, showing Amp., an Ampulla with a medusa
enclosed in it; Can. i, the living canals; Can. 2, the dying and degenerating
canals ; Cor., the Coralluni ; D., the Dactylozooids ; Ect., the external sheet of
Ectoderm; G., the Gasterozooids ; Med., the free swimming Medusae; Tab., the
Tabulae. Slightly modified from Moscley and the Cambridge Natural History.

HYDROZOAN CORALS 147

not always present ; in fact, specimens of the kinds shown in
Fig. 68 may be regarded as rarities in our collections, for,
unlike many other Hydrozoa, Millepora does not produce
its medusae continuously or over a long period of time,
but so far as we can judge only occasionally and then in
great profusion. But our knowledge of the periodicity of
medusa production in Millepora in any part of the world
is still lacking in precision.

Passing now to the structure of the living tissues which
form the corallum we find that there are two kinds of
polyps — the gasterozooids and the dactylozooids — inhabiting
the gasteropores and dactylopores respectively. The gas-
terozooids are short and stumpy polyps projecting only a
little way above the surface of the corallum when fully
extended (Fig. 67, G.). They have a terminal mouth and a
digestive cavity, in which occasionalh^ a small crustacean
may be found as food, and round the mouth are four knobs,
armed with nematocysts, which probably represent four
rudimentary tentacles.

The dactylozooids (Fig. 67, D.) when fully extended are
long, slender, hollow structures provided with a variable
number of short capitate tentacles arranged alternately or
more irregularly on the body wall. They have no mouths.
There can be no doubt that the function of the dactylozooids
is to catch and paralyse the small living organisms that
come within their reach and to pass them to the gasterozooids
to swallow and digest — an admirable example of efficient
division of labour. The zooids are connected together
beneath the surface by an elaborate system of branching and
anastomosing coenosarcal canals. These canals are pro-
vided with a double lining of cells. The outer layer of cells
— the ectoderm — is mainly concerned with the secretion of
the calcium carbonate that forms the corallum. The inner
layer of cells — the endoderm — may serve the purpose of
providing the ciliary action necessary for the maintenance
of the circulation of currents of water through the canals,
but on that point further investigation on living material is
needed. The most striking feature of the canal system is
the presence, in enormous numbers, of the symbiotic

148

CORALS

organisms called zooxanthellae, the function of which has
been discussed in a previous chapter (p. 20).

The coenosarcal canals are confined to the outermost
layer of the corallum. Down to the level of the first tabula
(Can. I in Fig. 67) they are alive and functional ; below that,
for a distance represented by two or three tabulae, they are
shrivelled and degenerating, and below that again they
disappear altogether.

Thus when a branch of a Millepora preserved in spirit,
say half an inch in diameter, is
treated with acid and the corallum
dissolved away, the whole system
of canals and polyps is represented
by a film not more than -^J^ of an
inch in thickness.

The colonies of Millepora are
richly supplied with nematocysts,
and as some of them are powerful
enough to pierce the human skin,
causing a painful form of nettle-
rash, the Millepora is regarded as
a stinging coral. The nematocysts
are of two kinds : a smaller kind
found in the tentacles of the zooids,
armed with four sharp spines at
the base of the filament, and a
larger kind without spines but with
a much longer filament which are
scattered over the surface of the
coenenchym between the zooids (Fig. 69).

The reproduction of Millepora is of extraordinary interest,
because it presents us with the only example that is known
of a stony coral that produces free-swimming medusae. The
medusae are produced in great numbers, they are of a very
simple structure, and when a colony is examined, are found
to be of the same sex, either male or female, and at approxi-
mately the same stage of development.

There are many points about this production of medusae
in Millepora on which we are still in ignorance. It is not

Fig. 69. — The nematocysts of
Millepora. A, The large kind
with the thread discharged.

B, The same before discharge.

C, The small kind with thread
discharged. D, The same before
discharge. x 700 diams.

I'lc. 68. — iMillepora. A part of a colony showing the surface profusely pitted
with ampullae. Nat. size.

HYDROZOAN CORALS 149

known, for instance, whether they are produced periodically
or spasmodically, or whether their production is due to
environmental conditions that affect all the Millepores of the
reef at the same time, and it is also not known at what size
or age they first begin to produce medusae.

All that can be said at present is that when the collections
of corals in museums are examined very few specimens are
found that exhibit the ampullae in which the medusae are
lodged, and this suggests that the phenomenon occurs at
long intervals of time and does not last long.

The medusa consists of an umbrella and a short stumpy
manubrium, which is, in some cases, provided with a mouth
in the female medusae but never in the male (Fig. 67, Med.).
The umbrella is extremely thin, and bears neither radial nor
ring canals. Close to its margin there are four or five knobs,
each one consisting of a battery of nematocysts, but apart
from this there are no tentacles. In the ripe female medusae
four or five relatively large yolk-laden eggs are borne by the
manubrium. In the ripe male medusae the testis is in
the form of a ring round the manubrium. The size of the
medusa in both sexes is about 0-4 mm.

It is very improbable that the medusae have a long free-
swimming life, and Mr. Duerden has observed that the
female medusae discharge their eggs within five or six hours
of their liberation.

Although Millepora occupies such an isolated position in
the animal kingdom, for it has really no near relation among
the corals, there is no evidence that it had made its appear-
ance on the reefs even as late as the Tertiary geological period.
It is true that a number of corals which have been given the
name Millepora by various authors are found in the Tertiary
and even older rocks, but a careful examination of these
fossils shows that not one of them possesses the very dis-
tinctive characters of the corallum of Millepora.

The only fossil coral that approaches Millepora in struc-
ture is the genus Axopora from the Eocene of France, but
this coral has monomorphic pores and each pore bears in its
centre a minute spine or columella.

Millepora is a common constituent of the coral reefs of

150 CORALS

the world, but it has been found also in depths of 20 to 40
fathoms off the Maldives.^

The Order Stvlasterina. — The second Order of
Hydrozoan corals is called the Stylasterina, and it is repre-
sented by two common and widely distributed genera —
Distichopora and Stylaster — and several others of rarer
occurrence.

As in Millepora, there is a massive corallum of calcium
carbonate which is perforated by a plexus of canals, and
there are two kinds of pores — the gasteropores and the
dactvlopores. In the common genera mentioned above, the
coralhuTi can easily be distinguished from that of Mille-
pora bv the presence of styles in the gasteropores, and by
the absence of tabulae. In some of the deep-sea genera,
however, there are no styles, and tabulae are occasionally
present in the gasteropores. The style is a little calcareous
column, usually covered with minute tubercles and spines,
which is situated in the centre of the pores like the columella
of a Madreporarian coral (Figs. 71 and 12).

The gasterozooids of the Stylasterina resemble those of
Millepora, except that the endoderm is reflected over the
style so as to provide more digestive surface, and each
gasterozooid has a mouth and four short tentacles. The
dactylozooids, on the other hand, differ very markedly from
those of Millepora in being very short, in having no tentacles,
and in possessing a scalariform endoderm which entirely
blocks up the cavity. The plexus of canals which forms
the coenenchym is not so close as it is in Millepora, and the
living tissues penetrate much deeper down into the substance
of the corallum. The nematocysts are very small and
simple in structure, and are confined to the tentacles of the
gasterozooids and the ectoderm of the dactylozooids. There
are no nematocysts at the surface of the coenenchym.

The Stylasterina do not produce free-swimming medusae,
but the eggs and sperms are formed in ampullae. In each
ampulla there may be one or more cups of folded endoderm
called the trophodiscs, each of which supports and nourishes

1 J. Stanley Gardiner, Fauna and Geography of the Maldive and
Laccadive Archipelagoes, vol. i. part 3, p. },2^.

HYDROZOAN CORALS 151

either a testis or a simple large yolk-laden egg, or it may
contain a larva and a withered trophodisc. The trophodisc
is sometimes provided, in the male, with a central column
of endoderm, called the Spadix, which resembles the
manubrium of a medusa, and by some authors the tropho-
disc is regarded as a degenerate medusa. This is, however,
a matter that requires further investigation.

P'lG. 70. — Distichopora. Surface view of a branch showing the ampullae.
■: 2 diams.

The ampullae can usually be seen at the surface of the
corallum and have the appearance of a cluster of blisters
each about 0-5 mm. in diameter (Fig. 70) ; and in all the
genera that have been examined, sexual reproduction appears
to be continuous, the gonophores in various stages of develop-
ment being found in nearly all the full-grown specimens.
The sexes are usually separate. Very seldom does a colony

152

CORALS

produce both male and female gonophores at the same time.
Only one case of hermaphroditism has been recorded in
Distichopora.^ The eggs are fertilised and undergo the
early stages of their development within the ampullae, and
when the female ampulla bursts, there emerges a free-
swimming planula larva. The Stylasterina are therefore
\'i\'iparous.

DiSTiCHOPORA. — The genus Disticho-
pora, formerly known as red or violet
sugar coral (Rumphius) or Millepora
violacea (Pallas), forms a flattened,
fiabellate, and sparsely branched coral-
lum rarely exceeding 4 or 5 inches in
height and is almost invariably brightly
coloured (violet, red, orange, or brown).
The pores are situated on the edges of
the branches in three rows, a middle
row of gasteropores flanked on each

t, -^. side by a row of dactylopores (Fig. 71).

^ '-?" In some places the rows of pores pass

on to the flat sides of the branches for
a short distance. The ampullae are
seen in clusters, sometimes on one only,
sometimes on both sides of the flat sur-
faces of the corallum (Fig. 70). When a
branch is examined in section, and for
this purpose a section made in the plane
of the pores is the best, each gasteropore
is seen to be provided with a long,
slender style. The pores have a long
curved course and penetrate almost to
the centre of the branch, but they are not, as a rule,
divided into partitions by tabulae.

Distichopora may be found in rock pools and in shallow
sea water in the tropical regions of the old world and in the
West Indies. A few specimens have also been found in
deeper water in the West Indies (100-270 fathoms) and in
the Indian Ocean (150 fathoms).

1 H. M. England, Trans. Linn. Soc. xii., 1909, p. 347.

Fig. 71. — Distichopora.
'Edge view of a branch
showing the arrange-
ment of the gasteropores
in a median line ; the
dactylopores on each
side of them. On the left
may be seen a cluster of
ampullae. :■: 2 diams.

HYDROZOAN CORALS 153

Stylaster. — The other genus of Stylasterina that is
very common is Stylaster. This coral forms profusely
branched flabellate colonies which sometimes attain to a
great size and when found in shallow water often possess
such a beautiful rose-pink colour that they are used for
ornamental purposes. The older branches of these Styl-
asters are very hard and are frequently mistaken for the
precious coral, but as they are perforated by the pores and
by the canal system they do not readily take a smooth polish
and are consequently of little value as jewels or charms.

This coral can be distinguished from the precious coral by
two characters. In the first place, the branches are far more
numerous and terminate in very delicate twigs which may
be only 2 mm. in diameter. In the second place, there
can be found densely clustered on the terminal branches, and
more sparsely on the larger ones, a number of cyclo-systems.

These pore-cycles in Stylaster are frequently raised on a
little prominence above the general surface of the corallum,
and when examined with a magnifying glass exhibit a
number of radially arranged ridges which have a striking
resemblance to the septa of a Madreporarian coral. When
the pore-cycles are prominent in this wa}^ they are usually
called " calices," although there is no true homology between
the calyx of a Stylaster and the calyx of a Madrepore (Fig. 72) .

In each of these calices there is a centrally placed pore —
the gasteropore — and close to the margin a circle of ten or
more dactylopores. In each of these pores there is a short
tuberculated st\de which has a very rough resemblance to
a shaving brush. The ampullae can be seen as rough ex-
crescences between the calices in almost every specimen
that is examined.

Stylaster is a genus with an extraordinarily wide geo-
graphical distribution. It is found in shallow water in most
of the tropical seas and in the deeper waters as far down as
900 fathoms. The deep-sea species are usually white, and
the calices are situated on one surface only of the flabellum.

Allopora. — Closely related to Stylaster is the sub-
genus Allopora, which is found in the deep fjords of Norway
and British Columbia, and in 50 fathoms off the Cape of

154 CORALS

Good Hope. As in Stylaster, both the gasteropores and
the dactylopores are provided with styles, but the caHces
are not so prominent, the ampullae are inconspicuous, and
the terminal branches relatively thick and blunt.

AUopora nohilis of the Cape is the largest and most

I'lG. 72. — Stylaster. A small part of a branch highly magiiitifd to show the
cyclo-systt'ins. Note the styles in the centrally placed gastcropore and in the
surrounding dactylopores. x 20 diams.

robust of all the Stylasterina. It seems to construct great
submarine forests in some localities which effectually pre-
vent successful dredging, as the great solid stems, over an
inch in diameter, are firmly fixed to rocks on the bottom.
Errina.^ — Of the remaining genera, Errina, with its

' S. J. Hickson, " The genus Errina," Proc. Zool. Soc, igi2, p. 876.

HYDROZOAN CORALS

155

two sub-generic forms Labiopora and Spinipora, appears to
be the most widely distributed. The pores are not arranged
in this genus in regular cyclo-systems, but are more or
less irregularly scattered over the surface of the branches.
The characteristic feature, however, is that some of the
dactylozooids, or all of them, are protected by blunt
processes of a cylindrical shape with a deep slit down one
side, called by Moseley the " nariform processes." A
better name for them, perhaps, is grooved spines (Fig. y ;'■,).

Each gasteropore is provided with
a short " shaving-brush " style, but,
as in Distichopora, the dactylopores
have no styles.

The genus is very ^^idely distributed
in water of from 100 to 500 fathoms
in depth, and recently some beautiful
coloured specimens have been found in
shallow water off the South Island of
New Zealand, off Cape Horn and the
coast of Chili, and in the Antarctic
Seas.

Sporadopora is a rare genus from
deep water, which has close affinities
with Distichopora, but it is of special
interest, because it has superficial
resemblance to a ramose colony of
Millepora, the colour being white, the
texture of the corallum being more spongy and brittle than
in most Stylasterina, and it has pores scattered irregularly
over the surface. Moreover, the resemblance is accentuated
by the fact that there are usually a few well-marked tabulae
in the gasteropores.

The structure of the polyps and the gonophores, however,
prove conclusively that Sporadopora is not, in any sense, a
connecting link with the Milleporina.

The remaining genera are of comparatively rare occur-
rence, and the only point of special interest about them is
the remarkable lamina or scale which protects the cyclo-
system in the genus Cryptohelia.

Fig. 73. — Errina (Labio-
pora) aspcra. Note the
characteristic grooved
spines protecting the
dactylopores. :■, 5 diams.

156 CORALS

The following table may be of assistance in identit\'ing
the genera of the Stylasterina :

A. Pores irregularly scattered —

(a) With styles in the gasteropores :

(i) Dactylozooids unprotected . Sporadopora.
(2) Dactylozooids protected b\'

grooved spines . . . Errina.

(b) Without styles Pliobotlinis.

B. Pores arranged in rows .... Distichopora.

C. Pores arranged in cyclo-systems —

{a) \\'ith styles in gasteropores and

dactylopores Sty last er.

(b) Without styles :

(i) Cyclo-systems protected by a

lamina .... Cryptohdia.

(2) Cyclo-systems unprotected . Conopora.

Allopora is now regarded as a sub-genus of Stvlaster,
characterised by having relatively thick, blunt, terminal
branches, and less prominent calices and ampullae.

Steganopora and Astylus have only been recorded once
from deep water. The former is closely related to Plio-
bothrus, the latter to Conopora.

Labiopora and Spinipora are sub-genera of Errina.

CHAPTER VIII

POLYZOAN CORALS

" Experiment is the Test of Truth, and that should always be made
before we wholly assent or dissent. But if Facts come well attested
by Persons of Judgment and Credit, however extraordinary they
may seem they deserve civil Treatment till they be examined fully."
— Henry Baker, I.e. p. 215.

The group of animals known by the names of Polyzoa or
Bryozoa affords several examples of skeleton formation that
leads to the construction of ramified, massive, or encrusting
calcareous and coral-like growths.

The polyps, or " zooids," as they are more usually called,
which construct these structures are so widely separated
from the polyps of the Madreporarian corals in structure
and development that, on morphological grounds, objections
may be raised to their consideration in any treatise with the
title of " Corals." But the fact remains that some of the
Polyzoa do form calcareous skeletons resembling corals so
closely that they will continue to be called corals by many
people who are interested in marine zoology but possess no
expert knowledge of the groups.

In many cases it is quite an easy matter to determine
whether a given specimen of coral has or has not been pro-
duced by a colony of Polyzoa, but there are others in which
a very careful examination with a strong magnifying glass
is necessary before the determination can be made with
certainty.

There are, however, still some corals, both recent and
fossil, of which there are only the hard skeletal parts to
serve as a guide ; these have been attributed to the Polyzoa,

157

is8

CORALS

but may have been formed by the zooids of some other group
of animals. It must be admitted, therefore, that, although
in most cases the structure of the dried Polyzoan coral is
sufficient to determine definitely that it is a Polyzoon, there
are some of them which exhibit no characters of the skeleton
that can be regarded as conclusive of their zoological
affinities.

The only definite proof that a given coral is a Polyzoon
must be obtained bv an observation of the structure of

the polyps which construct the
coral, and a few words must
therefore be written to explain
the essential features of the
anatom}' of this
animals.

\Mien
colony of

group

an
a

expanded living
Polyzoon is ex-
amined, the polyps are seen to
protrude and to display a crown
of long ciliated tentacles ar-
ranged to form a funnel, at the
base of which is a centrally
placed mouth (Fig. 74). By
such characters they might
be mistaken for Coelenterate
polyps, but further examina-
tion reveals a second opening
just above the crown of ten-
tacles, and a bent tube or
alimentary canal is seen through
the transparent body wall which connects these two openings
to the exterior. The presence of this complete alimentary
canal is quite sufficient to distinguish the Polyzoan polyps
from the polyps of any other group of animals that form
corals, but there are many other anatomical characters,
which it is not necessary to describe in this book, by which
the Polyzoa differ from other coral-forming organisms, and
exhibit what is usually regarded as a much higher t3'pe of
organisation.

Fig. 74. — Diagram to illustrate
the structure of a Polyzoan polyp.
p., the protrusible part of the polyp
with a crown of tentacles surround-
ing the mouth ; z., the thick outer
wall of the non-protrusible part of
the polyp or zooecium, which is
frequently calcareous ; a., the anus.
The bent alimentary canal is seen
leading from mouth to anus and
attached to the base of the zooecium
bv a band of muscles.

POLYZOAN CORALS 159

It is rarely possible to get the chance of seeing these
corals alive and expanded, but specimens which have been
preserved in spirit and examined in thin sections or in slices
cleared in oil usually show the essential characters quite
distinctly.

The body wall of the polyp may be divided into two
regions, one of which is always thin and usually transparent
and is capable of being protruded with the tentacles, and
the other, which is thick and opaque and is connected with
the other polyps of the colony. The latter region forms a
receptacle called the " zooecium " into which the expansible
part of the polyp can be withdrawn telescopically for pro-
tection, and it is this part which secretes the calcareous
substance in the Polyzoa described in this chapter. The
outer wall of each zooecium is perforated b}' a large aper-
ture through which the polyp protrudes in expansion, and
this is called the " orifice," and may also be perforated
by a variety of other smaller apertures according to the
genus and species under observation. In many forms the
orifice is not flush with the surface of the zooecium, but
mounted on the end of a short spout-like projection which
may be called the " collar."

There are no solitary calcareous Polyzoa, but every
species consists of a colony of many polyps whose zooecia,
firmly adherent to one another, build up the various kinds
of branching, net-like, or encrusting structures of the
Polyzoan corals.

Most of the calcareous Polyzoa form little tufts of very
delicate branches or thin spreading plates on shells or
stones, and the term " corallines " is more generally applied
to them than " corals," but it is just as impossible to give
a scientific definition of the former as it is of the latter. All
that can be said is that when the word " coralline " is used
it has reference to something smaller or more delicate in
structure than what are commonly called " corals."

The Poh'zoa are classified as follows :

Sub-class I. Entoprocta.

„ , , (Order I. Phvlactolaemata.

2. hctoprocta - r- ' ^ ^

^ .,2. Gvmnolaemata.

i6o CORALS

The Order Gymnolaemata is again divided into three
Sub-orders :

Sub-order i. Cyclostomata.

2. Cheilostomata.

3. Ctenostomata.

Of the various groups into which the Class is thus divided,
only two Sub-orders, the Cyclostomata and Cheilostomata,
provide examples of Polyzoa with calcareous walls. In the
others the walls of the zooecia are either horny, mucilaginous,
or free from any protective secretion.

Cyclostomata. — The coral structures formed by the
Cyclostomata usually consist of calcareous tubes with a
single circular orifice at the terminal extremity. These
tubes are usually closely bound together in bundles for the
greater part of their course, and in some genera the bundles
of tubes become so densely calcified that their tubular
nature cannot be determined by superficial examination,
although it is indicated b}/ the end which bears the orifice
projecting freely on the surface of the zooecium, and it can
be readily seen in transverse or longitudinal sections of the
main branches of the colonies.

Crisia. — One of the commonest and most widely dis-
tributed of the Cyclostomata is the genus Crisia (Fig. 75).
On our own coasts little bushy tufts of Crisia ehurnea are
often found attached to the zoophytes and seaweeds that
are cast up on the beach after a storm. They are not more
than one inch in height, and when seen by the naked eye
might be mistaken for the alga Corallina officinalis (see p.
207). An examination with a low-power magnifying glass
at once reveals their fragile tubular structure, and the large
round orifices of the zooecia enable the naturalist at once
to separate it from the coralline Algae.

In the species referred to, the branches are composed of
tubular zooecia arranged alternately right and left, and
almost entirely adnate, the orifices being only slightly raised
from the surface on short tubular projections.

An important feature of the genus is that at intervals in
the course of the branches the hard calcareous structures

POLYZOAN CORALS

i6i

are replaced by thin horny joints. It is extremely interest-
ing to find in this group the same " admirable contrivance of
Nature " of hard and soft joints for resisting the violent
motions of the sea that has already been mentioned as
occurring in some of the Alcyonaria (p. 121), and will also be
recorded in the Gymnolaemata (p. 172) and in the chapter
on Coral Algae (p. 207). It cannot for a moment be suggested
that the Polyzoa are genetically related to the Alcyonaria
or to the coral Algae, and therefore we must consider
that this admirable contrivance
has been attained independ-
ently in the course of evolution
and forms a fine example of
the principle of " convergence "
in Nature.

There is just one more
feature of interest in the OV
structure of the Crisia
colony to which reference may
be made in passing, as it is
characteristic of the Cyclosto-
matous Polyzoa.

On some of the branches
of the colony a swollen pear-
shaped body may be seen
which has the appearance of
a distorted or abnormal
zooecium (Fig. 75, OV). This

is an " ooecium " or " ovicell," and is formed for the
protection of the embryos. Ovicells also occur in the
Cheilostomatous Polyzoa, but they are not usually so con-
spicuous as they are in the Cyclostomata.

In the family Tubuliporidae the colonies usually form
little encrusting masses and spreading branches adherent
to foreign objects, but, if erect, as some of them are,
they do not exhibit the horny nodes seen in the genus
Crisia.

The delicate fragile branches and the small size of most
of the genera of the Cyclostomata give them an appearance

Fig. 75. — Crisia eburnea. A small
fragment of a colony. OV, an
ooecium. x 25 diams.

l62

CORALS

which would be described in the hmguage of popuhir natural
liistory as " coralline " rather than " coral."

HoRNERA. — In the genus Hornera (Fig. 76) the principal
branches arc much more solid, and, owing to the abundance
of the calcareous secretion, the greater part of the tubular
zooecia are said to be " immersed," that is to say, the out-
lines of the tubes are not visible at the surface. The result
of this is that the colony as a whole has a much more " coral-
like " appearance than the others. The colonies are erect,
profusely branched, and frequently
fan-shaped or flabelliform. When
examined with a lens the little spout-
like collars, from which the zooids
protrude, are seen to be arranged on
one side of the branches only, and
thus the fan-shaped colony may be
said to have a proper or anterior
surface and a reverse or posterior
surface. This arrangement of the
zooids on one surface only of a fan-
shaped corallum is not confined to
the Polyzoa but occurs in some of
the Stylasterina and Madreporaria
that live in deep water, and may be
due to the tendency of the zooids as
they are formed to turn towards the
source from which the food supplies
come to them. In shallow sea-water,
where the corals are subject to the
ebb and flow of the tides, the food comes to them first from
one side and then from the other, and the zooids are usually
arranged on all sides of the branches, but in deep water
there is frequently a prevailing current in one direction and
the zooids become grouped on one side so as to face it.

On the terminal branches of Hornera the outlines of the
zooecia are faintly indicated (Fig. 76), but the older branches
have a much smoother coral-like surface owing to the
zooecia becoming immersed by the increase of calcareous
deposit.

l"iG. 76. — Hornera liche-
noides. Terminal branch
of a specimen from off the
Shetland Islands. View of
the side on which the zooecia
open. X 7 diams.

POLYZOAN CORALS 163

There are no horny nodes in Hornera, and consequently
the coraUum is perfectly rigid.

The two species of this genus which occur in the British
area are seldom more than an inch in height and occur in
deep water (20-200 fathoms) attached to other corals and
foreign objects.

The particular interest of the genus is that it is one of
the many corals that were referred by Linnaeus and the
earlier writers to the genus Millepora, and was called by
him the Lichen millepore on account of its resemblance
to his Lichen fruticulosus seu foliaccus. The genus Mille-
pora is much more restricted now than it was in the time
of Linnaeus, when it served as a receptacle for any kind
of coral whose affinities could not be more accurately deter-
mined. No naturalist of modern times would refer Hornera
to the Milleporina, but there is a certain resemblance to
be seen between some forms of Hornera and the Stylasterine
genus Errina (see p. 154), and there can be little doubt,
judging from the excellent drawings which illustrate their
memoir, that the species described by Jullien and Calvet ^
as Hornera verrucosa is really a species of the genus Errina.

Heteropora. — The genus Heteropora has been the
subject of a good deal of controversy and has been mistaken
for a Millepora. It has now been definitely identified as a
Polyzoon, and its affinities are probably with the Cyclo-
stomata rather than with the Cheilostomata.

It consists of a broad attached base from which a number
of short dichotomously branched stems arise which end
bluntly. A large specimen may be 4 or 5 inches in diameter
and the branches 10-20 mm. in height by 5-6 mm. in dia-
meter. The substance is hard and calcareous, and the
surface is perforated by numerous small pores of various
sizes. These pores are clearly not of two categories, large
and small as in Millepora, but vary from a minimum
diameter of 05 mm. to a maximum of -3 mm.- When seen
in vertical section these pores are found to pass down into

1 Catnpagnes scientifiques du Prince de Monaco, fasc. xxiii., 1903.
- These measurements are taken from a specimen of H. pelliciilata
from New Zealand.

i64 CORALS

long tubes running more or less parallel with one another
into the depths of the branches.

Heteropora has been regarded as the last survivor of
a group of fossil Polyzoa called the Treposomata, which
occur abundantly in certain Palaeozooic rocks and had
some representatives in Jurassic times. It has also been
described as a Tabulate coral, but the fact seems to be that
in some specimens the tubes are divided into compartments
by thin calcareous tabulae and in others they are not. The
first of the recent specimens were found in the shallow
waters of New^ Zealand, and the genus has more recently been
discovered off the coast of South Africa and off the Pacific
coast of North America. An examination of specimens from
these three localities has show^n that in all general characters
they are very similar to one another, and perhaps represent
only one widely distributed species which should be called
Heteropora pelliculata} But although a few widely separated
tabulae were found by the author in specimens from New
Zealand, no trace of such structures were found in the
South African and Pacific coast specimens.

Cheilostomata. — In the Cheilostomata the colony
usually consists of a number of cubical oval or oblong
chambers (the zooecia) provided with a semicircular or
crescentic or sometimes circular orifice protected by a
chitinous lip or operculum, a second aperture situated just
behind the other in some cases, and numerous minute pores
arranged in various ways (see Fig. 78). The general effect
produced by this structure of the Cheilostomata when a
colony is examined with a lens, is to give the impression that
it is composed of a large number of closely fitting cells
(Fig. 80), and it is this cellular appearance under a low
power which mav be taken as the first rough guide to the
determination of a coral as a Cheilostomatous Polyzoon.

The only other coral with which it could possibly be
confused might be one of the large Foraminifera such as
Gypsina ; but from that it can at once be distinguished

^ Heteropora magyia, O'Donoghue, from Victoria, B.C., S-i8 fathoms,
may be a distinct species, but H. pelliculala also occurs in the same
locaHty {Contributions to Canadian Biology, N.S., vol. i., 1923, p. 156).

POLYZOAN CORALS

165

by the presence of the large orifice for the protrusion of the
Polyzoan polyp.

Retepora. — One of the commonest objects in a museum
collection of Polyzoa is the beautiful little coral frequently
called " Neptune's basket " (Manchette de Neptune, Tour-
nef) (Fig. ^^).

Its most characteristic form is that of a shallow bowl,
from one to two or three inches in diameter, attached by
a short round stalk to a shell or stone. The bowl is per-
forated throughout by numerous round holes or fenestra
about 075 mm. in diameter, situated at regular intervals
apart so that it has
the appearance of a net
or basket, and was in
consequence given the
name Retepora by Im-
perato in 1599. Later
observers, noticing
that the upper surface
of the coral exhibited
a large number of
minute pores, classified
it with many other
corals under the general
name Millepora, and
thus it became the Millepora cellulosa of Linnaeus.

The genus Retepora has a wide geographical distribu-
tion, being commonly found in the temperate seas, in the
Mediterranean, and in the Tropics. There are two British
species, both found in deep water : R. heaniana occurring
off the coast of Northumberland and Scotland, R. couchii
in the Channel Islands and off the coast of Cornwall.

The colour of the coral is usually white, but in some
localities (Torres Straits, Bass Straits, etc.) pink or salmon-
coloured specimens are not uncommonly found. The bowl
shape of the colony, which is by far the most characteristic
form, is in some specimens replaced by a more irregular
manner of growth leading up to forms that may be called
foliaceous ; but in these varieties the characteristic features

I'"iG. 77. — Retepora. Nat. size.

1 66

CORALS

of the coralliim and even the size of the perforations remain
remarkably constant. It is one of the easiest corals to
recognise and name.

Adeona. — Specimens of the exotic genus Adeona, found
in shallow water off the coast of Australia, Africa, and in
the South Seas, attain to the largest size of any of the
coral-forming Polyzoa. They consist of thick erect fronds
attached by a short flexible stalk to rocks, and they are
perforated by a number of round fenestra larger and more
scattered than in Retepora.

Some very large fronds of this genus, measuring two feet

in height and nearly
W*^^ ■ ♦ S ""^^ % '»~V» ;>*''''•■*■ cis much in diameter,
r**> ***l\f%'f''H^^ ♦ J;H^ ♦ l^a^'e ^e^" found, and,
I *k' # V«^^ 'i^^sW-'-r •^'irST^ as their substance is

hard, calcareous, and
of considerable thick-
ness, they possess a
thoroughh" coral-like
aspect.

At first sight
x\deona might be
considered to be a
large coarse species of
Retepora, but a de-
tailed examination of
the zooecia shows that
it is only remotely related to that genus. Among other
points of difference that may be observed is the presence
in Adeona of a second large aperture situated a little dis-
tance behind the orifice and frequently connected with it
by a shallow groove (Fig. 78). This second aperture is
smaller than the main aperture but distinctly larger than
the pores which decorate the sides of the zooecia.

Closely related to Adeona is the genus Adeonella, which
forms masses of variously branched or ramified coral
substance sometimes attaining considerable dimensions.
The stem in this genus is not flexible as in Adeona, but the
colony is usually attached to some flexible support.

Fig. 78. — Adeona. Surface view of a part
of a colony. : : 20 diams.

POLYZOAN CORALS 167

Lepralia. — In dredging in a few fathoms of water off
the British coast, the naturahst sometimes finds his net
held up or checked by large masses of a foliaceous coralline
substance which proves to be a Cheilostomatous Polyzoon
belonging to the genus Lepralia {L. foliacea). The first
record of this species seems to be that of Ellis, who wrote :
" This stony Millepora was found growing to an oyster
shell on the west coast of the Isle of Wight in April 1753,
and when it was received the Insects were visible in the cells
but dead." He called it the " Stony foliaceous coralline "
or Eschar a niifoi'iiiis.

Fig. 79. — Lt'pral ill foliacea. From Plymouth. J nat. size. Photo by H. Jiritten.

The specimen which was photographed for the illustra-
tion (Fig. yq) was taken off the Mewstone Rock near
Plymouth in 1923 in about 12 fathoms of water, and
occupied a space of about one cubic foot, but larger speci-
mens than this are not uncommonly found off the coast of
Cornwall.^

When a piece of one of the thin and very brittle laminae
or leaves of the coral is broken off and dried, the surface on
both sides is seen to be composed of typical Polyzoan zooecia

' Couch mentions that he had seen one hooked up by a lisherman off
the Eddystone which measured 7 feet 4 inches in circumference and i
foot in depth (Hincks, British Mari}ie Polyzoa, p. 304).

i68

CORALS

arranged in rows (Fig. 80), and the student of zoology will
recognise a close similarity between these zooecia and those
of the common sea-mat, Flustra. One of the most important
differences between Lepralia and Flustra is that, w^hcreas
in the former the walls of the zooecia are impregnated with
calcareous matter, in the latter they remain horny in
texture. From this difference it follows that in Lepralia
the fronds are rigid and brittle, whereas in Flustra they
are flexible and tough.

Cellepora. — The genus Cellepora includes some species
which form, in tropical waters, large spherical, oval, or

irregularly shaped masses
of coral substance (Fig.
81); but as the walls of
the zooecia are relatively
thin the texture of these
masses might be called
spongy, and they feel light
in the hand as compared
with other corals.

In these tropical species
the lumps of Cellepora
are frequently invaded
by other organisms which
seem to live and thrive
without material incon-
venience to their host.
In one ramified specimen from shallow water off the Aru
Islands the surface is perforated by little round holes,
situated at approximately equal distances apart, in which
were Uving sea anemones. In other specimens barnacles
and worm tubes are found.

When these lumps of Cellepora are cut across it is generally
found that there is a core or kernel of some foreign substance,
such as a stone, another coral, or a branching Gorgonian, upon
which the Polyzoon has built up layer upon layer of zooecia
until the original support is entirely submerged. The final
shape of the lump is due in large measure to the shape of the
foreign substance on which it started to form its colony.

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Fig

80. — Lepralia fuliacia.
of a part of a colony.

Surface view
16 diams.

POLYZOAN CORALS 169

Cellepora is not the only genus in which these lumps of
coral of irregular shape are formed by the overgrowth of
successive laminae of zooecia. Lumps of Polyzoa 3 or 4
inches in diameter formed by the zooecia of the genera
Microporella and Schizoporella are not infrequently found.

These can be distinguished roughly from the more
abundant Cellepora by the smaller size of the zooecia.

It is difficult to give, without going into detailed account

Fig. 81. — Cellepora. From oft .\ucklaiid, New Zealand. Xat. size.

of Polyzoan structure, the precise characters by which these
genera are distinguished from one another by the special
workers in this group, but as Cellepora is such a widespread
genus it may be of interest to state the characters which
serve as a guide to its recognition.

The zooecia of Cellepora are described as flagon-shaped
(urceolate) and erect, the end of the zooecium which bears
the orifice projecting from the surface, while the base is
more or less submerged. The size of the zooecia varies a

170

CORALS

good deal, but as a roiigli guide for comparison with other
species, it may be said tliat the average length of a zooecium
is about 0-3 mm.

The zooecia appear to be irregularly disposed with a
tendency to overlap and form layer upon layer of super-
imposed laminae. The walls of the superficial zooecia are
very thin and brittle, and there does not seem to be the same
tendency for the walls of the lower layers to become thicker,
so that the colony as a whole retains its light spongy texture.

Fig. 82. — Porella ccniprcssa. From west coast of Scotland. Xat. size.

The genus Cellepora includes a very large number of
species and several of them are represented in British waters.

One of these, C. pumicosa, is very commonly found
attached to the seaweed and zoophytes cast up on the beach
after a storm. It has the form of little white, or if fresh,
pink dome-shaped encrusting masses of zooecia a quarter of
an inch or less in diameter.

Porella. — This cosmopolitan genus of Polyzoa includes
a species of coral, P. compressa, which is not uncommonly
brought up in the dredge off the coast of Cornwall, off the
west coasts of Ireland and Scotland, and in some other
British localities. It seems to be confined to deep water

POLYZOAN CORALS

171

{i.e. 30-200 fathoms). The colony is three or four inches in
height and is profusely branched more or less in one plane,
the branches freely anastomosing. The terminal branches
are usually flattened or compressed and terminate in blunt
points, or where they are about to bifurcate, in broad heart-
shaped expansions (Fig. 82).

The main stem and the thicker branches are cylindrical,
and the calcareous substance of which they are composed
appears to be much harder and more compact than the
stems of other calcareous Polyzoa, but a close examination
of their structure in transverse section shows that they are
built up of concentric rings of zooecia with thickened walls.
At the surface the zooecia
are seen to be largely
submerged, but the orifice
of each one is raised on
a short conical projection
and this gives a rough
file -like texture to the
branches (Fig. 83). On
the flat terminal branches
the surface is smoother,
and as the walls are thin-
ner the complete outline
of the zooecia can be
more clearly seen.

Porella is a very large genus, and among the many species
a great variety of form of growth is observed. Some
species are erect and ramified like Porella compressa, others
are flat and encrusting, forming large circular patches on
rocks and stones such as the common British shallow-water
species P. concinna.

The genus Smittia is closely allied to Porella in the
structure of the zooecia and some species reach a considerable
size. S. landsborovii, for example, which occurs in British
seas, has a foliaceous variety which might be mistaken for a
small specimen of Lepraliajoliacea, but it can be distinguished
from the species by the presence of a small tooth-like pro-
jection on the lower lip of the orifice of the zooecium.

Fig. 83. — Poi't'll.i compressa. Surface
view. On the right a part of a branch
showing the zooecia ; 8 dianis. On the left
a single zooecium ;■; 20 chams.

172

CORALS

Cellaria. — The genus Cellaria (Fig. 84) must be briefly
referred to, partly because it includes a very common and
widespread species and partly because it affords us another
example of a jointed colony, calcareous internodes being
connected together by tubular horny nodes.

Cellaria fistulosa is one of the commonest of the British
corallines, extending from shallow to deep water in many
localities off our own coast, but has also been recorded in

the Indian Ocean, off New
Zealand, Australia, the Cape
of Good Hope, and other
distant places, so that it
may be regarded as a
cosmopolitan species.

It forms typical little
coralline tufts or shrubs
some two or three inches
in height, attached to
rocks or shells, consisting
of numerous cylindrical and
jointed branches dividing
dichotomouslyat the nodes.
The internodes are calcar-
eous and are formed by a
large number of zooecia
arranged usually in longi-
tudinal rows. They are,
of course, very variable in
size, but in a typical speci-
men, say from the Firth of
Clyde, the internodes may be found to have a length of
10 mm. and a diameter of 0-5 mm. The horny nodes are
very short, o-i mm. in length, but quite sufficient to give the
colony the necessary flexibility to yield without breaking to
the movement of tides and currents.

In the description that has been given in the preceding
pages of a few representative genera of calcareous Polvzoa,
some idea may be gained of the range of form and structure
of coralline skeleton found in this group. It ma\' also serve

Fig. 84. — Cellaria fistulosa. Firth of
Clyde. The specimen on the left drawn
to iiat. size.

POLYZOAN CORALS 173

to assist the collector to distinguish the Polyzoa from other
corals. But the scope of the present work does not permit
any attempt to be made to give such a detailed account of
the very large number of genera which are included in the
group as will enable him to identify his specimens and give
them the correct names they should bear in his collection.
Both the Orders of calcareous Polyzoa, but particularly the
Cheilostomata, present many difficulties for the systematist.
Like many other animals that lead a sedentary life and form
plant-like colonies by the rapid asexual reproduction of the
polyps, there is a very wide range of variation in the general
form and in some of the details of structure, so that there
is some difficulty in drawing the boundary lines between
closely related genera and species. It is necessary, there-
fore, for the naturalist to consult the special memoirs on the
group 1 if he wishes to get the correct names for his specimens.

From the frequent references that have been made to
the occurrence of calcareous Polyzoa off the British coasts it
may be inferred that this group of corals is well represented
in the waters of the temperate regions of the world. It is
not necessary for the naturalist to visit the coral reefs of
the Tropics if he wishes to find abundant material for their
study. He will be able to discover as rich a fauna of this
description in European waters as anywhere else.

The warmer tropical waters of the world might seem to
be less favourable for the growth of Polyzoa, because these
relatively small corals are apt to be lost sight of among the
bewildering complex of huge and fantastic zoophytes of
other Orders that are crowded together in every locality of
the sea-bottom that is suitable for the growth of corals.
But it has been shown that when the marine fauna of tropical
waters is carefully and criticall}' examined a great abundance
and a great variety of calcareous Polyzoa can be found. It
is probably not a fact that tropical water is unfavourable

1 T. Hincks, History of the British Marine Polyzoa, 1880 ; G. R. Vine,
Report on Recent Marine Polyzoa : Reports of British Association Meeting
at Aberdeen, 1885, vol. Iv. References to more recent memoirs and
treatises will be found in the works of JuUien and Calvet ; Campagnes
scientifiques du Prince de Monaco, fasc. xxiii., 1903, and S. F. Harmer,
Reports of Siboga Expedition, livr. Ixxv., 1915.

174 CORALS

to tlic life of tlu'se creatures, but that it is so favourable to
tlie growth of others of similar habits tliat they seem to be
lost in tlie crowd.

Two examples of large numbers of a calcareous Polyzoon
occurring in a tropical locality which have attracted the
attention of the author of this volume in recent years, may
be referred to in order to emphasise the point that such
localities are not necessarily unfavourable for the study of
the group.

Lagenipora. — In a sample obtained by Mr. Townsend
of a shelly sea-bottom from a depth of 156 fathoms at the
mouth of the Persian Gulf, large numbers of specimens of

a Chcilostomatous Polyzoon were
found which belong apparently to
the genus Lagenipora. They con-
sist of little dome-shaped colonies
about 5 mm. in diameter formed
b\- 50-100 flask -shaped zooecia
arranged radiallv from the centre
(Fig. 85).

There are two curious points
for consideration about the occur-
FiG. 85.— Lagenipora. From rence of Lagenipora in this spot,
the Persian Gulf, 156 fathoms, j^^ ^^le first place the geuus has

X lodiams. _ ^ o ^

hitherto been found only in the
glacial Arctic region and on the British coast. It seems
strange, therefore, that it should be discovered in a locality
where the surface waters are probably as hot as they are
anywhere in the world and at such a long distance from
their other habitats In the present state of our knowledge
it might be premature to say that this is a case of discon-
tinuous distribution, but it is, at least, an interesting example
of many that are found in the same group of a wide geo-
graphical distribution of a genus. In the second place, all
the specimens are free. There is no evidence to be found of
any basal plate of attachment or of any supporting substance,
and none of the great variety of shells with which it was
found were suitable in character to give them a permanent
upright position.

POLYZOAN CORALS 175

All the specimens show signs of being more or less water-
worn, and it is probable, therefore, that they do not live in
the spot where they were found but have been carried there
from some other locality by the sea currents. When this
locality is discovered and complete living specimens have
been examined, some of the problems that have arisen from
the discovery of these interesting corals will perhaps be
solved.

Haswellia. — The other example was found in a collec-
tion of Alcvonaria made by Professor Haddon from shallow

Fig. 86. — Haswellia. From Torres Straits. A part of a terminal branch.

X 10 diams.

water in the Torres Straits. Attached to the Alcyonaria the
author found large numbers of a delicate branching coralline
Polyzoon belonging to the genus Haswellia (Fig. 86). The
most characteristic feature of this genus is that the zooecia
are arranged in more or less regular whorls of five or six and
are cylindrical in shape, and in the older branches almost
completely submerged. The verticillate arrangement is indi-
cated by the rings of short collar-like tubes on which the
main aperture of the zooecia is mounted. In the specimens
from the Torres Straits the largest complete colonies are about
two inches in height and the branches are about ^V i'^-ch
(i mm.) in diameter.

CHAPTER IX

FORAMINIFERAN AND SOME OTHER CORALS

" J 'ai bien constate que toutes les loges sont occupees a la fois
par la substance glutineuse ; mais je n'ai point vu les expansions,
non plus que dans le Polytrema, que je conjecture appartenir a cette
meme familie (les Infusoires) d'apres la nature de la partie vivante."
— DujARDiN, Suites a Buffon : Infusoires, p. 259.

The Foraminifera are best known to naturalists as the
constructors of the minute flask-shaped, oval, or chambered
shells that are found, sometimes in immense numbers, on
certain sands of the sea-shore or in the mud of the abysmal
depths of the ocean, and it might seem to many that it
would be quite out of place to include any of them in a treatise
on Corals. And yet there are some calcareous structures
formed undoubtedly by these primitive protoplasmic
organisms which have been classified with other corals in
the past history of zoology, and to this day might very
readily be regarded as the production of some Coelenterate
or Polyzoan organisms unless carefully examined.

It is true that the vast majority of Foraminifera are
free and carry their calcareous skeletal structures with them
as they slowly creep along on the seaweed or drift at the
surface of the sea, and to such structures the word " shell "
of our common language is correctly applied. But when,
as in the cases to be described in this chapter, the calcareous
structure is permanently fixed to a foreign substance, which
may be a stone or a rock or a piece of seaweed, and grows
and branches into a tree-like form or constructs layer upon
layer of calcareous chambers to form a thick crust upon its
support, the word " shell " is not appropriate. The only

176

FORAMINIFERAN AND OTHER CORALS 177

common word in our language which really conveys the
correct idea of their general form and structure is the word
" coral."

Many of the multilocular shells of the Foraminifera have
a spiral form similar to the shell of the pearly Nautilus
and some of its fossil relatives, and it was this resemblance
in form which led D'Orbigny into the error of supposing
that the Foraminifera were microscopic Cephalopods. The
discovery of the protoplasmic consistency of the body and
of the delicate network of pseudopodia they emit was made
by Dujardin, who definitely and correctly placed them in
the division Rhizopoda of the great group of unicellular
animals called the Protozoa.

PoLYTREMA. — The most familiar and probably the most
abundant of all the Foraminiferan corals is Polytrema. It
has usually the form of a short branching coral-like structure
4-5 mm. in height attached by a flat and sometimes spreading
base to a foreign body. It has generally a pink or carmine-
red colour, but white varieties have been found in many
localities. It has a wide distribution in the warm and
tropical waters of the Old World and Pacific Ocean, but,
strange to say, is very rare in the West Indies and tropical
waters of the Eastern American coasts. It is extremely
abundant in the Mediterranean Sea, being found attached to
corals, zoophytes, to the leaves of Zostera, and to Algae of
various kinds. In some places broken, water-worn, but some-
times remarkably perfect specimens form an important con-
stituent of the sands cast up on the shore. Among the most
remarkable of these sands are the " sables rouges " near
Ajaccio off the coast of Corsica, which owe their red colour
to the vast numbers of whole or fragmentary specimens of
Polytrema. It was in these sands that Mr. Heron-Allen dis-
covered the rich material for his description, to which refer-
ence will presently be made, of the important stages in their
life-history before and after fixation to a foreign substance.

The first description of Polytrema is that given by
Pallas in 1766, who classified it with that heterogeneous
medley of corals called Millepora by the older writers. It
had previously been seen by Tournefort (1700), who made

178 CORALS

tlie grie\-()us blunck'i" of supposing it to be the young stage
of the true Red coral {CoraUiuni nohilc) ; but it \\-as the dis-
tinguished French naturahst Dujardin who, having observed
in 1841 a " substance glutineuse " in the chambers, placed
it tentatively among the Rhizopoda.

The genus has since been thoroughly investigated by
Mobius, Merkel, and other investigators, and its place in
the group of the Foraminifera has been firmly established.

It is not necessary to describe in detail the structure
and life-history of the organisms that form the shells and
corals of the Foraminifera, but it may be said that by no
extension of the meaning of the words can they be called
" polyps " or " zooids." They consist of a mass of the
granular semi-fluid living substance called Protoplasm
and show no differentiation into cells and no structural
organs. There are no tentacles, no mouth, and no defined
digestive canal or cavity. Embedded in the substance of
the protoplasm there is a nucleus or, in some stages of the
life-history, several nuclei.

The food of the Poh'trema is obtained by a network
of very delicate but anastomosing protoplasmic filaments
which project from the ends of the branches. These fila-
ments are called the Pseudopodia.

\Mien the dried calcareous structure of the Polytrema
(Fig. 87) is examined carefully with a lens, the surface of the
base and of the branches is seen to be perforated by a
number of minute holes. There are two kinds of holes, the
larger kind called the " pillar pores " and the far more
numerous smaller kind called the " foramina " (Fig. d>d>, A).
The sub.stance of the coral below the surface is built up by
the perforated calcareous walls of a number of chambers
which are arranged more or less concentrically at the base,
but are much more irregular in the stem and branches. More-
over, in the axis of the stem and branches there is a tendency
for the cavities of the chambers to fuse so as to form an
irregular but continuous lumen, the branches thus becoming
hollow or tubular.

This lumen ends at the extremity of each of the branches
in a large irregularly round aperture, and projecting from the

FORAMINIFERAN AND OTHER CORALS 179

lips of this aperture there may be seen in well-preserved
specimens a number of needle-like spicules. The presence
of these spicules carefully arranged in this position to act
as scaffolding poles for the support of the new chambers
as they are formed has given rise to some controversy.
They are not composed of the same chemical substance
(calcium carbonate) as the walls of the chambers and are
not solvible in weak acids, and it is generally supposed that
they are the siliceous spicules of some sponges which the
pseudopodia have collected from the surrounding medium
and placed in this
position.

The habit of col-
lecting the spicules of
sponges, grains of
sand, and other foreign
bodies, and incor-
porating them in the
skeletal structures is
found in many other
genera of Foramini-
fera, so that in this
respect Polytrema is
not peculiar; b'ut
there are many inter-
esting questions that
arise about this habit which require further careful investiga-
tion. It is, for example, very difficult to understand how the
Polytrema can find the required spicules in some localities,
how they can select spicules of the proper length and kind,
and how they are dissolved at a later period when the
calcareous secretions have surrounded them in the con-
struction of the chambers.

As a final word in this very brief account of the structure
of Polytrema it should be said that the calcareous skeleton
is extremely brittle. The stem and branches can be easily
crushed between the finger and thumb. This is in striking
contrast to the next two genera to be described in this
chapter, which are more solidly built.

Fig. 87. — Polytrema miniaccum. \ branch-
ing specimen attached to a piece of RamuUna.
The fragile ends of the branches are broken off,
showing the chambers. x 3 diams.

i8o

CORALS

There are still some gaps to be filled up in our knowledge
of the life-history of Polytrema, but it is known that before
the young Polytrema becomes fixed to its support it lives
a free life like the majority of the Foraminifera and possesses
a shell of three or four chambers which has a close re-
semblance to the shells of the genus Rotalia. This stage is
known as the " rotaliform young." At a subsequent stage,
when successive chambers have been formed around the
primary ones, it assumes a roughly globular form like a
raspberry, and if this stage continues and it becomes more
irregular it assumes a form like that of some species of

. « • - '

:;•::

Fig.

-Surface views of A, Polytrema ; B, Homotrema ; C, Sporadotrema.
X about :;o diams.

Gypsina. If the Gypsina-like form finds a suitable object
it becomes attached to it and constructs an irregular thin
plate of chambers, connecting it with its host, which sub-
sequently increases in thickness and submerges the primary
chambers. At a later stage the beginning of the stem is
seen arising as a dome in the centre of the upper surface.^

The account that has been given of the general form of
the full-grown Polytrema applies to specimens which have
been able to develop freely in comparatively quiet waters
or sheltered places. But the coral is so brittle that the
stem and branches are very liable to be broken off in their
natural habitat in the sea, or more particularly in the process
of collecting and the subsequent handling of the specimens.
It thus comes about that the most familiar form of Poly-
trema is not the branching form but that of little pink

^ For a full account of this development see Heron- Allen and Karland,
Zoology of the " Terra Nova " Expedition, xo\. vi. No. i, 1922, p. zzi.

FORAMINIFERAN AND OTHER CORALS i8i

encrusting discs on corals or shells, which may or may not
show the scars of the broken-off stems. Specimens of this
kind can frequently be found on the dead branches of other
corals or on shells from tropical waters of the Indian and
Pacific Oceans.

HoMOTREMA. — Until quite recently the genus Homo-
trema has been confused with Polytrema on account of its
size, colour, and habit, but a detailed study of its structure
proves that the two genera are quite distinct.

If corals and shells from the reefs of the West Indies
be examined they will frequently be found to bear little
red spots and discs very similar to the spots and discs of
Polytrema found on corals and shells from the Mediterranean
Sea and the East Indies, and some of them may support
short knobbed processes something like a
minute pollarded willow tree (Fig. 89).

Pallas seems to have noticed two of
the characters which distinguish Homo-
trema from Polytrema, for he says that
the specimens from American seas are of
a darker red colour than those from the
Mediterranean Sea, and that they have

. -^ Fig. 89. — Homotrema

the form of large irregular warts from rubnim. :< 2 diams.
the surface of which a few short branches
spring.^ But Pallas did not feel justified in separating the
two varieties, and included them both in his species Mille-
pora miniacea.

The characters that separate Homotrema from Poly-
trema may be summarised as follows : The form may be
that of a simple encrusting disc, but, when standing erect
from a spreading base, of the shape of a wart or knob with
sometimes a few very short projections at the free extremity.
The surface is mapped out into areas which are slightly

^ " Color hujus elegantissimi Corallioli ex mari Mediterraneo allati,
pallide roseus esse solet, interdum saturatior. Quod in coralliis Indicis
reperitur pulchre cinnabarinum colorem exhibet ; saturatissimum vero
specimina in Coralliis testisque exesis Maris Americani reperiunda.
Americana varietas plerumque verrucae magnae inequalis speciem habet,
quae superficie sparsos ramulos exserit." — Pallas, Elenchus Zoophytorum,
1766.

i82 CORALS

convex and perforated by minute foramina surrounded by
solid imperforate boundaries (Fig. 88, B). There are no
pillar pores. The colour is almost invariably of the dark
red tint which is technically known as salmon colour. No
white varieties have been found. In addition to these
characters, which can be observed without dissection, there
are other characters of the internal chambers which separate
the genus clearly and distinctly from Polytrema.

The most curious fact about the two genera is perhaps
that of their geographical distribution. A very large number
of dried corals and shells from various islands of the West
Indies and the Western American coasts have been examined,
and without exception the red foraminiferan discs attached
to them have invariably shown the Homotrema characters.'

In the Mediterranean Sea Polytrema is very abundant,
and Homotrema does not occur. In the tropical Indian and
Pacific Oceans both genera occur, and sometimes specimens
of the two are found on the same piece of coral, but on the
whole Polytrema is the more common. In the New Zealand
area Polytrema was found by the Tei'va Nova expedition to
be abundant, but no specimens of Homotrema were obtained.

No specimens of either genus have been found either in
the Arctic or Antarctic Seas.

vSporadotrema. — The third genus of this series of
Foraminifera is Sporadotrema, which more fully justifies its
place in a book on corals in being larger and more robust
than the other two.

The first specimens of this genus to be discovered were
found by Captain Warren in the Gulf of Manaar and were
described by Carter under the name Polytrema cylindricum ;
but the richest collection of specimens was made by Stanley
Gardiner, dredging in water 30-150 fathoms in depth in the
Indian Ocean. '^

Specimens have also been found in Torres Straits, off the
Phihppine Islands, and in the tropical Pacific Ocean. The

1 Since the above sentence was written one specimen of Polytrema
from I^arbadoes has been found.

- S. J. Hickson, Transactions of the Linnean Society of London, vol. 14,
1911.

FORAMINIFERAN AND OTHER CORALS 183

Fig. 90. — Sporadatrema cy-
Undricum from Providence
Island, Indian Ocean, 70
fathoms. :'. 2 diams.

genus is not known to occur in the Mediterranean Sea or in
the West Indies.

In the case of Polytrema and Homotrema the specimens
from various parts of the world are
so much ahke, both in form and
minute structure, that it is reason-
able to suppose there is only one
species of each genus ; but in the
case of Sporadotrema it is necessary
to divide the genus into two species,
5. cylindricum and 5. mesentericum.
The form of Sporadotrema cylin-
dricum is always erect, a thick solid
stem springing from a restricted base
and giving rise to a few thick
branches (Fig. 90). No flat disc-
shaped encrusting specimens have

yet been found. The surface of the stem and the proximal
parts of the branches are perforated by a number of

foramina of relatively large
but variable size and irregu-
larly scattered. There are no
areolae and no pores (Fig. 88,
C). In some specimens, the
chambers of whicli the corals
are composed (Fig. 91) are
indicated on the surface at the
ends of the branches by a
number of convex areas per-
forated by relatively large
foramina.

Another very striking char-

FiG. 91. — sporadotrema cvlindrtcum. . , . . , ,

Photograph of a section through a actcr ot the SpCClCS IS the COlour

specimen showing the chambers and variety. Some Specimens are

the thick outer wall perforated bv the -^ -^

foramina, x 5 diams. ' dark purplish red, others pmk,

yellow, or orange coloured.
Large specimens are over an inch in height and in expanse,
and many specimens just under an inch both ways are to be
found in the collections. Although size is not as a rule an

i84 CORALS

important character in the determination of corals, it is so
in this case, because the two genera with which Sporadotrema
cylmdricmn is most hkely to be confused never exceed a
quarter of an inch in height.

It may have been thouglit at one time that Sporadotrcvia
cylindriciim was only a robust and overgrown variety of
Polytrema, but there is no foundation for this belief. The
two genera are quite distinct. Apart from important differ-
ences of detail in the structure of full-grown examples of the
two genera which it is not necessary to describe in this place,
the young immature stages are as distinct as the adults. A
young Sporadotrema growing on the same support as a
larger specimen of Polytrema exhibits
all the important characters of its genus
and could not be mistaken for a young
specimen of either of the other two
genera.

Sporadotrema mesenterictim (Fig. 92)
appears to have a much more restricted
range than that of S. cylindriciim, hav-
ing been found only in shallow water in
Fig. gz.spomdutrcma Torres Straits.

mesentericum homTovv^s jj^^ ^^^^ ^f ^j^-g gpecics is character-

straits. X 2 diams. _ _ ^

istic, as it consists of a number of more
or less erect sinuous laminae arising from a spreading
encrusting base. The margin is thick and crenate. The
laminae are sometimes interlaced so as to form a kind of
labyrinth of laminae, but in the simple condition of a single
lamina the form has a rough resemblance to a cock's comb.
In full-grown specimens the laminae are 15-20 mm. in
length, from 7 to 8 mm. in height, and from 1-5 to 2 mm.
in thickness.

All the known specimens are of a salmon-red colour. As
regards the surface characters and general structure the
species does not differ in any material respects from 5.
cylindricum, and it clearly belongs to the same genus.

Gypsina. — The genus Gypsina (Fig. 93) is a Foraminifer
which, like many others, sometimes becomes attached to
some rock or shell and forms encrusting discs or laminae ;

FORAMINIFERAN AND OTHER CORALS 185

but the great majority of these encrusting Foraminifera do
not attain to a size of more than a milHmetre or two in
diameter and need not, therefore, be referred to in detail.
There is, however, a variety of Gypsina plana which reaches

Fig. 93. — Gypsina. Gypsina plana. In-oin Mauritius, loo fathoms. Nat. size.

such a gigantic size — for a Foraminifer — that it might well
be mistaken for a coral of another Order.

Like other Foraminifera the substance of Gypsina plana
is built up of minute
chambers with walls per-
forated by the foramina,
and when the young free
form becomes adherent
to a stone the chambers
increase in numbers at
the circumference and by
the formation of laminae
after laminae of new
chambers growing over
the surface of the old
ones (Fig. 94). In some
specimens obtained by Prof. Stanley Gardiner in deep
water (25-100 fathoms) in the Indian Ocean these laminated
masses of Gypsina have formed a thick crust entirely
surrounding their original support, and have the appearance

'•o^Oi><^:

Fig. 94. — Vertical section of Gypsina plana
showing the perforated chambers. From a
drawing In' Miss Lindsev. :■: 120 diams.

i86 CORALS

of lum])s of water-worn coral reaching a size of 3-4 inches in
diameter.

The general appearance of these large encrusting forms of
Gypsina is much like that of some other corals of a similar
habit described in this book, and the occurrence of Fora-
minifers of this size is so extremely rare that it would not
be surprising if a collector of corals in general were to make
a mistake in classifying them. A few notes may therefore
be written to describe the principal characters by which
they can be recognised as Foraminifera.

The surface of the coral when magnified exhibits a
number of closely fitting and slightly convex areolae varying
in size from 70 to 230 microns [i.e. -07- -23 mm.). These areolae
representing the outer walls of the chambers of the superficial
lamina are perforated by numerous foramina. They might
be thought to be the walls of the zooecia of a calcareous
Polyzoon, but they differ from them in the absence of the
large aperture or orifice for the protrusion of the Polyzoan
polyp.

The only other kind of coral for which they might be
mistaken would be the calcareous algae, but the surfaces of
the calcareous algae have either no areolae (cf. Halimeda,
p. 210), or if they show in some places convex areolae (cf.
Fig. loi, facing p. 201), these areolae are not pierced by
more than one foramen.

There is one more point of interest about these large
specimens of Gypsina plana. They are so much bigger than
the specimens of Gypsina (not exceeding 1-2 mm. in diameter)
with which the student of the Foraminifera is most familiar,
that it may seem remarkable that they have not been
relegated to a distinct genus.

Fortunately, however, it has been possible to examine ^
a large number of specimens from the smallest to the largest,
and it has been found that not only is there a fairly complete
series as regards the size of the specimens (i-ioo mm.), but
also as regards the size of the constituent chambers (20-230
microns).

* M. Lindsey, Transactions of the Linnean Society of London, vol. 16,
1913-

FORAMINIFERAN AND OTHER CORALS 187

Ramulina. — One of the most remarkable results of the
recent oceanographic investigations has been the revelation
of the extraordinary variation of the constitution of the
sea-bottom in areas situated a few miles from the coast-line.
There are various designations given to express the nature
of these deposits, all of them more or less vague and inde-
terminate— such as " mud," " sand," " shell," " gravel,"
" rock," and " coral." In the hope of giving some assistance
to those who wish to use a more precise designation to a
so-called " coral " sea-bottom deposit, a description is given
in this book of various kinds of coral which play an important
part in the formation of
such deposits in various
parts of the world.

One of the most in-
teresting of these is the
deposit discovered by
Herdman along the 100
fathom line about 12
miles south of Galle in
Ceylon. In this locality
the dredge brought up Fig. 95.

f 1 From Ceylon. Nat. size.

masses of a calcareous

structure from |- to over 2 inches in diameter, which was
named by Dakin Raiinilijia Jierdmani. Unfortunately noth-
ing is known for certain about the living organisms that
form these calcareous structures, but there are sufficient
reasons for believing that they are Foraminifera.

" They consist of a mass of anastomosing calcareous tubes
inextricably commingled and assuming two principal forms
of growth. Many specimens show a long series of globular
segments, arranged irregularly, and opening directly into
one another by large openings. These globular chambers at
intervals give off numerous radiating straight tubes varying
in length from quite small outgrowths to 1-25 centimetres
with a diameter of 1-5 mm. to 2 mm. These straight portions
may run in the same direction, separating but little and
becoming compact, or they may diverge and radiate from
a common centre. Eventually they reach either the

-Ramulina herdmani.

i88 CORALS

globular cluunbers or other straight tubes with whieh they
fuse, the cavities becoming continuous " (I'igs. 87, p. 179,
and 95).

" All the walls are uniformly perforate, but the external
surface differs in appearance in places, being sometimes
quite smooth and elsewhere bearing minute denticles either
sparsely or more closely set. There also seem to be definite
larger openings to the exterior." ^

The genus Ramulina was founded by Rupert Jones in
1875, and seems to have a w^orld-wide distribution in depths
of 50-700 fathoms of water.

PoRiFERAN Corals

Merlia. — Among the many encrusting calcareous
organisms that have for a time puzzled the experts there is
no one more interesting and remarkable than Merlia
normani (Fig. 96).

At first it was thought to be a Pol^'zoon, then certain
characters were discovered which suggested the view that
it was a Foraminifer, but it has at last settled down into
a position among the Sponges, where it must remain until
some unexpected evidence is forthcoming to prove that it
has been wrongly classified. The first specimens to be
discovered were found in sixty fathoms of water off Porto
Santo Island near Madeira. They consisted, when dry, of
an encrusting calcareous substance covered by a thin yellow
pellicle.

On examining sections of this substance siliceous pin-
shaped spicules were found in the upper layers, and conse-
quently it was suggested that the yellow pellicle was the
remains of a sponge which had grown over and perhaps
smothered the organism that had formed the calcareous
substance.

It is well known that in the Order of the Sponges (Porifera)
one group of genera forms calcareous spicules and another
siliceous spicules, but it was considered to be very unlikely

^ Dakin, Reports on Ceylon Pearl Oyster Fisheries, 1906, v. p. 228.

FORAMINIFERAN AND OTHER CORALS 189

that any sponge would be found that formed both a sihceous
and a calcareous skeleton as well.

We are indebted to Mr. R. Kirkpatrick of the British
Museum, who made a special journey to Porto Santo to
obtain living specimens of Merlia, for a careful investigation
and description of fresh material and for the conclusion,
which seems to be convincing, that the calcareous substance
of Merlia is formed by the Sponge.^

All the specimens of Merlia that have hitherto been
described were found in deep water off Porto Santo or off
the coast of Madeira, but a very fine specimen was obtained
by Professor Gardiner off
Solomon Island in the
Indian Ocean, and it is
probable, therefore, that
the genus has a wider
geographical distribution
than was at first sup-
posed.

The living specimens
have a smooth surface

and are bright vermilion I-io. 96.-ilM'/ja norman^ Solomon island,
o Indian Ocean. Nat. size.

in colour, but when re-
moved from the sea the thin layer of fleshy substance
settles down and reveals the porcelain - like calcareous
skeleton.

The dried specimens have the appearance of thin crusts
of calcareous matter of irregular but roughly circular form
about 10-15 nim. in diameter, firmly adherent to some
hard support. Unlike many encrusting corals, Merlia cannot
be detached from its support without being hopelessly
destroyed. The character of the support varies. In the
Solomon Island specimen it is a mass of porous coral sub-
stance so much altered by age and boring organisms that
it is impossible to determine its precise nature. The Atlantic
specimens were attached to shells, branches of corallines,
worm tubes, a dead Dendrophylha, and a block of volcanic
rock.

' R. Kirkpatrick, Quart. Journ. Micr. Sci. Ivi., 191 1.

IQO

CORALS

W'licn the surface of the coral is examined with a lens
it is seen to be perforated by a number of cylindrical tubes,
and between these tubes the calcareous walls rise up in
polygonal ridges which are ornamented with columella-like
tubercles where the angles of adjacent polygons meet (Figs.
97 and 98).

If the specimens are sufficiently well preserved to show
these tubercles they present a surface character which is
quite sufficient to distinguish Merlia from any other coral,
but of course this character is the first to disappear if the
specimens are water- worn.

t;;

.jm,

JU.i^^r^ .1^

- ''i>.^:

^^-£^

^^7^5?*^^

Fig. 97. — Meilia normani. Photo of a vertical section through a fragment of
a specimen from Solomon Island showing the vertical tabulate tubes of which
it is composed. < 15 diams.

On examining a vertical section or fractured edge of a
specimen the most interesting character is seen in the
presence of a series of fiat tabulae dividing the cavity of
the vertical tubes into a number of chambers or " crypts."
Merlia is therefore a tabulate coral. The tabulae, however,
differ from the usual form of tabulae in the fact that they
seem to be always perforated in the centre by a little round
hole of communication between two adjacent crypts.

The investigation of fresh material has shown that the
sponge which forms this remarkable skeletal structure
belongs to the Family Haploscleridae and the Order Mon-
axonellidae, but its most curious character is that certain

FORAMINIFERAN AND OTHER CORALS 191

cells which appear to be of the general nature of amoebo-
cytes take upon themselves the function of secreting calcium
carbonate (calcocytes), and it is with these remarkable cells
that the crypts are filled.

AsTROSCLERA. — Another very remarkable calcareous
structure which seems to be undoubtedly the production
of a sponge is Asirosclera willeyana}

The type specimen from Lifu is a little hard calcareous
knob about 8 mm. in height by 5 mm. in diameter. The
stem is cylindrical and smooth with a spreading base attached
to a dead coral ; the upper end is convex and scored by an
irregular labyrinth of pits and grooves. j\ J\ a A
A specimen from Funafuti is shaped "'™«^^''~^ ■' -
like a short-stalked fungus with a disc
20 mm. in diameter. Other specimens
are more irregular in shape, but they
all show grooves and pits on the upper
free surface.

In a vertical section the interior of
the coral is seen to be penetrated by a
system of anastomosing channels, many
of which have a longitudinal direction
and eventually open to the exterior in
the pits of the upper surface. In fresh
specimens the soft tissues of the sponge
cover the distal surface and, extending
beyond it some little distance down the stem, penetrate into
the anastomosing channels in the corallum.

Astrosclera has hitherto been found in 35 fathoms of
water off Lifu in the Loyalty Islands, and in 100 fathoms
off Funafuti in the Ellice group.

Petrostroma schulzei. — Another sponge which forms
a hard calcareous structure is Petrostroma schulzei, found at
depths of 100-200 fathoms of water off the coast of Japan.
According to Doderlein "^ it represents a distinct family of
calcareous sponges which he calls the I.ithonina.

I'"iG. 98. — Diagram to
illustrate the strueture of
Merlia. X4odiams.

1 J. J, Lister in Willcy's Zool. Results, Part IV
Natural History, vol. i. p. 194.

- Doderlein, Zool. Jahrb., Syst. X., 1898.

1900 ; and Cambridge

192 CORALS

In external form it might be mistaken for a Millepora
or a Heteropora, as it consists of a broad base from which
a number of short C34indrical or flattened dichotomously
divided branches rise to a height of an inch or more.

When fresh the white coral substance is covered by a
white or yellow film of sponge substance and spicules, but
this disappears when it is dead and macerated.

The dried coral may be distinguished from other corals
by its spongy texture and the absence of any regular pores
or channels, but more particularly by the character of the
surface, which is provided with a number of small pointed
vertical pillars like a palisade. Among these pillars there
may be found some of the characteristic forked calcareous
spicules which are suflicient by themselves to suggest to
the naturalist that the structure must have been formed by
a sponge ; but a careful study of the coral with a lens shows
that the pillars at the surface and the subjacent structures
have been formed by the growth and fusion of these spicules.

Annelid Worm Tubes

In the examination of corals of various kinds the
naturalist frequently finds a number of long, straight, coiled,
or twisted calcareous tubes which have been formed by
different kinds of Polychaet worms.

In such a tangled mass of coral as that shown in the
illustration of Lophohelia (Fig. 5, p. 28) a number of such
tubes, distinguished by their smooth cylindrical contour
and the absence of septa, are invariably present. In Helio-
pora again the corallum is always perforated by small
tubes of the same kind (Fig. 52, p. 119). There are many
corals which possess some power of protecting themselves
from uninvited guests of this sort, but still it must be said
that most corals are liable to be penetrated by and frequently
distorted and disturbed in their normal manner of growth
by certain kinds of sedentary polychaet worms.

The relation between the hosts and the guests in this
association may not be clearly understood. It is difficult
to believe that the coral hosts are ever seriously incon-

FORAMINIFERAN AND OTHER CORALS 193

venienced by the worm guests. They may not grow into
exactly the same shapes as they would without them, but
they show no signs of reduced vigour or general health.
In some cases, such as that of Heliopora and Leucodora
(p. 119), the association appears to be constant, the Heliopora
always harbouring its Leucodora guests, but in others the
worms may or may not be present, and the corals without
the worms are apparently as healthy as those with them.
There is no reason, therefore, to suppose that the worms
in any way assist their coral hosts in the struggle for
existence. The association must be regarded as one of
commensalism, the host and guest feeding at the same
table, without injuring or benefiting each other.

It does not seem to be a case of mutualism such as that
of Heteropsammia (p. 78) and the Sipunculid worm, in
which both the host and guest benefit by the association,
and more certainly it is not a case of parasitism. The
worm must not be branded with the stigma of a parasite.

But although they are so often associated with corals
it must be remembered that the tubiculous worms are also
found in immense numbers living an independent life
attached to various kinds of solid objects. Every one must
be familiar with the little spiral tubes of Spirorbis attached
to the seaweed and stones that are washed up on the beach
and the larger meandering tubes of Serpula attached to
oyster shells. Not infrequently it is found that tubes of
Serpula will almost completely cover the shells on which
the}^ have settled, and sometimes they run over one another
in serpentine fashion to form lumps of intertwined calcareous
tubes several inches in diameter.

It is perhaps stretching our definition of the word beyond
its legitimate boundaries to call such lumps " coral." It
would be better if they could always be called " worm tubes."

But there is one of these Polychaet worms which forms
great masses composed of a lab3^rinth of small calcareous
tubes that are frequently many inches in diameter and
might readily be mistaken for a coral.

The genus Filograna (Fig. 99) seems to have an almost
world-wide distribution in shallow water, and sometimes is

194

CORALS

found in masses as big as a " boy's head " on the Scottish
and other coasts of Great Britain. It seems to be fond of
situations in which there is a good flow of water, and has
been found choking the supply pipes of an aquarium.^

The mass is built up of an immense number of small
branching calcareous tubes about 0-5 mm. in diameter, and
is hone3'combed with irregular spaces which harbour various
kinds of marine creatures (Fig. 100). It is not hard, as
coral substances usually are, but delicate and friable, and
unless handled with care breaks up into minute fragments.

The appearance of the living colonies of Filograna has

Fig. 99. — Filograna implexa. \ nat. size.

been described by Professor Mcintosh" as follows : " Fresh
examples from Plymouth in sea-water, as Huxley and others
truly said, resemble corals in so far as the branchial fans
of the annelids project from the tips of the tubes as miniature
flowers, the distal parts (branchiae) of which are pale greenish
yellow and the anterior region of a fine reddish hue which
tints the cephalic region at the base of the branchiae and
passes a short distance along each filament. When eggs
are present the posterior region is also reddish, the colour
of these being of a brighter hue than the front. Two dark

^ Prof. Mcintosh, " Notes from the Gatty Marine I^aboratorj', St.
Andrews," (xhi.), Ann. Nat. Hist, iii., 1919.
^ I.e. p. 149.

FORAMINIFERAN AND OTHER CORALS 195

eyes occur on the dorsum of the reddish cephahc area.
The anterior (thoracic) membrane is more deeply tinted in
front than behind. When in full vigour the pure white of
the calcareous tubes, the scarlet of the anterior region
which projects beyond them, and the pale greenish yellow
fans with their opaque tips make a picture at once beautiful
and characteristic."

Reference has already been made to the world-wide
distribution of this beautiful and interesting tubicolous

Fig. 100. — Filograna implexa. A small part of the mass of serpentine tubes.

X 5 diams.

worm, but to avoid misunderstanding it should be stated
that the species and varieties which have been described
by various authors under the generic name Salmacina are
here included in the genus Filograna. The only essential
difference which was supposed to separate the two genera
was the presence of an operculum to close the mouth of the
tube in Filograna and its absence in Salmacina, but Mcintosh
has shown, in a recent paper, that this character is so
variable, even in specimens from the same locality, that it
is quite unreliable for generic distinctions and considers

196 CORALS

that the most reasonable \-ie\v to take is that we are deahng
here with one species whicli is endowed with a remarkable
capacity for variation.

Accepting this view, it may be said that Filograna
implexa has been found in the Arctic Seas, off the British
and Norwegian coasts, in the Mediterranean and Red Seas,
in the Indian Ocean, and in Australian waters — a remark-
ably cosmopolitan distribution.

CHAPTER X

CORAL ALGAE

" Coralline is in a manner wholly spent among us to kill worms
in children and in elder persons, and as the matter so the manner,
but by what quality it worketh this effect is not declared by any,
for it is altogether insipide and without taste of heate or cold as
Corall itselfe is and if Corall be so much commended against the
stone and fluxes, crampes, the falling sicknesse and melancholly
etc. as you shall heare in its proper chapter doe not thinke but
these may conduce somewhat thereunto also." — John Parkinson,
Theatre of the Plants, 1640, p. 1296.

A GREAT many kinds of marine Algae have their cell walls
strengthened by deposits of calcium carbonate. Some of
these retain the softness of texture and the flexibility of the
non-calcareous Algae and could not possibly be mistaken
for anything else than seaweeds ; but a considerable number
assume such a hard texture and calcareous aspect that they
are called corals not only by fishermen and sailors, but even,
in familiar speech, by some men of science.

To separate these two groups of Algae is, of course, a
thoroughly artificial proceeding and cannot be justified on
any ground of vegetable morphology, but as the object of
this chapter is only to provide such information as will
enable the student to distinguish the vegetable from the
animal corals and to recognise some of the most important
forms, an artificial classification of this kind must be
employed.

The discovery, by Peyssonnel and Ellis in the eighteenth
century, that many of the corals are animals led un-
fortunately to a wider and erroneous generalisation that all
corals are animals.

197

198 CORALS

Linnaeus wrote a note to the genus Corallina : " Corallina
ad regnum animale pertinere ex substantia earum calcarea
constat, cum omnem calccm animalium esse product um
vcrissimum sit." Ellis ^ himself was of the same opinion
but was rather more cautious in expressing it. " What and
where the link is that unites the animal and vegetable
kingdoms of Nature, no one has yet been able to trace out ;
but some of these corallines appear to come the nearest to it
of anything that has occurred to me in all my researches ;
but then the calcareous covering, though ever so thin,
shows us that they cannot be vegetables." Pallas ^ dissented
from this view^ and in his introduction to the Corallinae said
that the whole of this genus should be handed over to
the botanists. Whereupon Ellis replied in a long letter
to Linnaeus, which was published in the Philosophical
Transactions of the Royal Society in 1767, that they were
unquestionably animals.

Lamarck (1816) included all the calcareous Algae in his
book on Animaux sans vcrtchres, but his most noteworthy
contribution to the subject was the introduction of the
word " Nullipores," which was accepted as a convenient
term for corals that did not show conspicuous pores. The
name was extended in its application in later years but
finally abandoned altogether when it became too vague
and indeterminate.

Some time before the year 1819 Targione Tozzetti
recognised that the corals belonging to the genus Halimeda
were plants, for he included them in his unpublished " Cata-
logus vegetabilium marinorum." Phillipi (1837) and Unger
(1858) proved that the greater numbers of the so-called
Nullipores are Lithothamnia and therefore plants. And
finally, in 1877, Munier-Chalmas recognised that the last
remaining family, the Dactyloporidae (Dasycladiaceae), are
calcareous Algae.

The study of calcareous Algae has revealed the fact that
marine plants belonging to widely separated groups of Algae

1 John Ellis, Natural History of the Zoophytes, 1786, p. no.

2 Elenchns Zoophytorum, p. 418: " Mihi vero totum hocce genus
Botanicis reliqucndum vidctur."

CORAL ALGAE 199

have the power of strengthening their waHs with calcium
carbonate, and thus assume an appearance superficiahy Hke
that of the animal corals.

It is difficult to estimate the important part that is played
by the calcareous Algae in building up and protecting the
coral reefs of the tropical sea, but it is not perhaps so well
known that they are found in such immense quantities at
the bottom of the shallow seas in extra-tropical regions,
including those of our own coasts, that they must influence,
to some degree, as in other climes the complex forces that
determine the fluctuations of the coast-line.

Class Rhodophyceae

Family Corallinaceae. — The most important of the
algal corals are undoubtedly those belonging to this family
of the red seaweeds. Some of them build up great encrusting
masses on the surface of other coral or rocks, others are in
the form of free knolls which are rolled over by the tide
so that all sides may be exposed at different times to the
necessary influence of the sunlight ; others again are attached
to a foreign substance but give rise to dichotomously branch-
ing dendritic growths.

In some regions of the world these Algae occur in such
enormous quantities that it is no exaggeration to say that
they constitute the floor of the sea.

In the course of the voyage of the Siboga, for example,
a bank of these corals off the Island of Haingsisi near Timor
was exposed at low water and was described by Madame
Weber van Bosse ^ as follows :

" The Lithothamnion bank struck me because it is such
a unique sight to see the ground, as far as the eye can reach,
covered by the pretty beautifully pink-coloured knolls,
which are heaped up so close together that, while walking,
one crushes them continually, making a peculiar noise as
of broken china."

The first observation to be made in determining the
systematic position of a coral that may belong to the

1 Corallinaceae of the Siboga Expedition, livr. xviii. 1904, p. 5.

200 CORALS

vegetable kingdom is the examination of the surface of a

dried specimen with a magnifying glass. If the surface is

found to be entirely imperforate and seems to be smooth

and even greasy to the touch, it is certainly a plant and

not an animal coral. It is probable, however, that no coral

has a surface which is really imperforate, and if a little chip

of the surface of such a coral be examined with a high power

of the microscope, the minute apertures of the superficial

layers of cells may be discovered. The coral Algae, however,

may be in fructification, and in that case the surface will

exhibit a number of more or less prominent convexities —

projecting conceptacles — and at the summit of each of these

convexities there is a pore of larger size, that is to say a

pore visible under a low-power magnifying glass (Fig. loi).

In such cases, if there is any doubt as to the nature of the

coral, the hard close texture of vegetable coral — if it belongs

to theCorallinaceae — and the characteristic cellular structure,

when seen in section under the microscope, are sufficient to

separate it definitely from any kind of animal coral and

establish it as a plant. The next observation to make

presents no difficulty and does not require the help of the

magnifying glass. It is to determine whether the thallus

is continuous in growth or jointed (compare Figs. 102 and

106). If it is continuous in growth it belongs to one section

of the family Corallinaceae, which may be called section A.

If it is jointed it belongs to the other section (B) of the

Corallinaceae or to another Order of Marine Algae (see

p. 210).

Section A of the Corallinaceae has been divided by
systematists into a large number of genera and sub-genera,
many of which are comparatively rare and will not be re-
ferred to in this chapter. The most abundant and widel}'
distributed of the unjointed Corallinaceae belong to the
genera Melobesia, Lithothamnion, and Lithophyllum.

The thalli of these three genera are so variable in form
that it is difticult to give any general definition of any one
of them that can be relied upon as a guide to the ready
determination of any given specimen. Many overlapping
forms occur which can only be definitely placed in their

Fig. lor. — Surface view of a Lithothamnion showing the bhster-hke swellings
and pores of the conceptacles. x 20 diams.

CORAL ALCxAE 201

systematic position by the skilled examination of the expert
in the group.

Melobesia. — The genus Melobesia consists of a number
of species which are usually found encrusting rocks or stones
or epiphytic on other Algae. They consist of thin plates
frequently round in outline, following closely the form of
their support and often fusing laterally with neighbouring
thalli to form continuous plates of considerable extent. At
the surface there may be seen prominent rounded or conical
protuberances which contain the conceptacles, and these are
perforated when ripe by a single median aperture. The
greater part of the thallus of Melobesia is only one layer of
cells in thickness, and as the members of this genus do not
increase in size vertically they never form thick massive
structures. It is only in the regions of the conceptacles that
the thallus is more than one layer in thickness.

There is one other character of importance that is of
assistance in the recognition of Melobesia, and that is the
presence of small hair-like processes which project from
the surface of the ordinary {i.e. not conceptacular) parts
of the thallus, giving the surface a somewhat velvety
texture.

This last character separates the genus Melobesia from
Heteroderma, which in other respects it closely resembles.

There are about sixty species of Melobesia and Hetero-
derma widely distributed and often verv abundant in the
tropical and temperate seas of the world.

LiTHOTHAMNiON. — The geuus Lithothamnion is even
more widely distributed and abundant, and the numerous
species exhibit an immense variety of form and structure,
some being encrusting plates, others forming papillate
clumps or free knolls, and others again growing into small
branching shrubs.

This genus can usually be distinguished from Melobesia
by the thickness of the thallus, which always consists of
several layers of cells, but confusion may arise between larger
specimens of Melobesia and young Lithothamnions unless a
critical examination of the microscopic structure is made.
The distinction between Lithothamnion and Lithophyllum

202

CORALS

is more difficult, but reference to that will be made at a later
stage.

The most familiar form of Lithothamnion is perhaps
the flat encrusting species (L. lenormandi) frequently found
encrusting stones and rocks at low tide on the British
coasts. It is usually of a dark salmon-red colour but becomes
pink or blanched when exposed to the sunlight. In deeper
water off our coasts another species {e.g. L. fascicnlatum)
may be found, sometimes in immense quantities, forming a
complete carpet over considerable tracts of the sea-bottom-.

This is a branched
fasciculate form.

Another form such
as that represented
by Lithothamnion
dimorphuni, also
found off the British
coasts, consists of
large irregular lumps
of coral several inches
across with a surface
covered with short
papillate or mammil-
late processes (Fig.

Fig. io::. — Lithothamnion dimorphmn from west
coast of Ireland. Nat. size.

102

The importance of
Lithothamnion lies in its widespread distribution and extra-
ordinary abundance. Thus on the coast of Spitzbergen and
Nova Zembla, Litliothamnion glaciale covers the bottom in
deep layers for several miles. L. ungeri forms banks off
Greenland. In temperate regions we have the Litho-
thamnion beds on the British coasts and such instances as
the NuUipore banks of the Gulf of Naples, which are mainly
composed of Lithothamnion ramulosum.

In the Tropics, reference has already been made to the
abundance of Lithothamnion on the reefs of Timor. Off
Tahiti rounded masses of this coral were found in lo
fathoms of water in such abundance that the dredge came
up tilled with them. Gardiner has also referred to its

CORAL ALGAE 203

occurrence in large quantities in various localities in the
Indian Ocean.

Many other examples could be given to illustrate the
wide distribution of this genus of calcareous Algae and of its
importance in forming and protecting the bed of the sea
in shallow waters. It extends from the Arctic seas to the
coral reefs of the Tropics, and wherever the conditions of
the tides and sea-currents are favourable for its growth,
whether in the cold waters of the arctic regions or the warm
waters of the equatorial regions, it seems to dominate the
position.

LiTHOPHYLLUM. — The genus Lithophyllum is another
calcareous Alga which is usually found encrusting rocks,
corals, and other animal and vegetable growths, following
the irregularities of its support and throwing up papilliform
or dome-shaped tubercles from its upper free surface. It
frequently becomes free by detachment from its original
support and then forms spherical or irregular lumps that
are rolled by the surf. Like other Rhodophyceae the living
coral has a pink or red colour, but specimens of Lithophyllum
which are dried and dead are nearly always white in contrast
to the specim.ens of Lithothamnion, which when dried usually
but not always retain a reddish colour. The specimens of
this genus often attain to very great dimensions, and on some
of the coral reefs of the Tropics form huge, massive or en-
crusting growths covering the greater part of the rocks
exposed to the breakers. There can be no doubt whatever
as to the very important part that is played by Algae of this
genus in the building up of the coral reefs, and in protecting
them from v.^ave action and other destructive agencies.

The genus Lithophyllum is more prevalent in the warmer
than in the colder seas, but specimens are found in all the
great sea areas, e.g. Lithophyllum (G) hrassica florida'^ in the
Mediterranean and Lithophyllum lichenoides of the British
seas.

It has already been mentioned that there is no character
which can be readily determined by the field naturalist or

^ I have included in this account of Lithophyllum the species attri-
buted to the genus Goniolithon by Foslie. Vide infra, p. 205.

204

CORALS

traveller and used by him to distinguish a Lithophyllum
from a Lithothamnion. There is so much variation in size
and form in both genera, and colour is such an untrust-
worthy guide to generic distinctions, that there are many
specimens which can only be determined by experts in the
group. Nevertheless, there can be no doubt that when
critically examined the genera are distinct, and a few words
may now be written to indicate the nature of the characters
by which they are separated. When a thin section of a part
of a thallus of one of these genera is examined, it will be
found to consist of many layers of minute cells with thick
calcareous walls (Fig. 103). The cells are roughly cubical

in shape and somewhere about
0-02 mm. in breadth. The layers
of cells are not uniformly ar-
ranged except in very young
growths, but exhibit oval or
spherical gaps that represent
the spaces in which the con-
ceptacles were placed. These
gaps may be about o-i mm. in
length.

There are three kinds of con-
ceptacles, one kind containing
the tetraspores or asexual repro-
ductive bodies, a second kind
for the antheridia or male re-
productive organs, and a third for the female reproductive
bodies (archegonia or cystocarps). It seems probable that
no one specimen or frond of a specimen bears more than
one of these kinds of conceptacles at the same time. The
ripe sexual conceptacle in both genera is roughly dome-
shaped in vertical section, the dome usually indicated at
the surface by a convexity perforated in the centre by a
pore, and it is extremely difficult to distinguish the sexual
conceptacles of the one genus from those of the other by
any characters that persist in the dried coral. The young
tetrasporangial conceptacles, however, do show an important
difference. In Lithothamnion they are perforated by several

Fig. 103. — Section of a piece of
the thallus of a Lithophyllum
showing the cells (about o-oa mm.
in breadth) with thick calcareous
walls and the surface (c, c) repre-
senting the gaps formed by old
conceptacles. 50 diams.

CORAL ALGAE

205

pores at the surface (Fig. 104), in Lithophyllum by only one
(Fig. io5).i

Another difference between Lithothamnion and Litho-
phylkim has been described. In the former there is a marked
distinction between the outer layers of small cubical cells
constituting the Perithallium and the inner layers of larger
and longer cells constituting the Hypothallium. In Litho-
phyllum the hypothallium is represented by a single layer
of cells or is entirely wanting.

Enough has been said, perhaps, to indicate to the reader
that there is a scientific distinction of some importance
between these two genera, and that the accurate determina-

FiG. 104. — Section of a tetra-
sporangial conceptacle of a Litho-
thamnion showing two tctrasporcs
(t, t), and the surface perforated b}'
several pores.

Fig. 105. — Section of a young
tetrasporangial conceptacle of a Litho-
phyllum showing two tctraspores (t, t),
the surface perforated by one pore and
a tuft of paraphyses {p) at the base.

Figs. 104 and 105 from Engler and Prantl.

tion of the character that separates them requires some
special skill and scientific appliances.

It has been noted (p.. 203) that many of the species of the
old genus Lithophyllum have been separated by Foslie
into a new genus Goniolithon. The difference between
these two genera lies in the character of the asexual con-
ceptacle. In Goniolithon the tetrasporangia are evenly
distributed over the floor of the conceptacles, whereas in
Lithophyllum they are formed only on its sides, the centre
of the conceptacles being provided with papilliform pro-
cesses called the Paraphyses (Fig. 105).

1 For further information on this point see A. Engler and K. Prantl,
Die natiirlichen Pflan:enfamilien, Nachtrag, igii ; NicoUs, University of
California Publications : Botany, vol. iii., 1908 ; and Mme. Paul Lemoine,
C. R. Paris, Feb. 15, 1909.

206

CORALS

There are two more coral Algae belonging to the family
Corallinaceae to which some reference must be made,
although neither of them play the same important part in
the construction of reefs and sea-bottoms as the corals that
have just been described.

They belong to the Group B (see p. 200) of coral plants
which show a discontinuous deposit of calcareous matter
so that both stem and branches consist of a series of cal-
careous joints linked together
by non-calcareous internodes.
This is the same " admirable
contrivance of Nature " that
has previously been described
in the Alcyonarian genus Isis
to protect the plants from the
violent motions of the sea
(see p. 121).

Amphiroa. — The first of
these is Amphiroa (Fig. 106),
a genus having a wide dis-
tribution in tidal and shallow
waters of tropical and sub-
tropical seas. In many locali-
ties, such as on the southern
coast of California, a species
of Amphiroa [A. calif ornica)
occurs in enormous quantities
in sea pools at low water, and
masses of it are thrown up on the beach by the waves.
The miniature forests of this bright purple - red coral
which cover the rocks in the shallow pools and form a
shelter for a great variety of little fish, Crustacea, and other
interesting kinds of animal life, are in the bright sunshine
the scene of a wonderful display of brilliant colours equal
only to what may be seen on a greater scale on the coral
reefs.

Although Amphiroa exhibits considerable variation in
size and in manner of growth, the plants are rarely more
than five or six inches in height, the joints being 3-6 mm.

I'"iG. 106. — Amphiruii califoniica.
Nat. size. The fragment on the left
X 2 shows the swollen conceptacles
at the ends of the branches.

CORAL ALGAE 207

in length. They usually branch dichotomously in one plane,
and the joints are flattened in the same plane and sometimes
expanded. There are some species, however, in which the
joints are cylindrical, as in Corallina.

The joint of an Amphiroa has the same hard texture
and the same smooth and greasy surface as the Litho-
thamnion group of genera, and an examination with a lens
does not reveal any pores or other apertures, except the
openings of the conceptacles on those joints that happen to
be ripe. It is therefore typically a Nullipore.

On microscopic examination of a joint, it is found to
consist of an enormous number of minute cells similar to
those of Lithothamnion although arranged rather differ-
ently. The nodes are composed of two or more rows of
these minute cells covered by a cortical layer of similar cells
differing from those of the joint in having very little or
no calcareous matter deposited in their walls, thus allowing
a certain amount of movement between one joint and the
next.

The conceptacles are formed in small blister-like pro-
jections from the surface of the joints and are most con-
spicuous on the terminal branchlets of the plant.

Corallina. — Another member of the family Corallin-
aceae is Corallina officinalis, a common alga in the rock pools
of our own coasts. Like Amphiroa on the Californian coast,
it is frequently found to cover the rocks with a miniature
forest of its slender delicate branches, of a pale pink or rose-
pink colour. On account of this habit and of its diminutive
size it was called by the older German writers the " Korall-
moos " or " Coral moss," a name which is very expressive
of its habit and of the soft velvety texture it seems to have
when felt by the hand immersed in the rock pool. But if this
" moss " is dried and examined with a lens, the coral-white
colour and the hardness of each separate joint reveal its
true position as a member of the family to which Amphiroa
and Lithothamnion belong.

It is a jointed coral hke Amphiroa, and the joints are
usually cylindrical in form, i mm. in length and 0-5 mm.
in breadth.

2o8 CORALS

The branching of the coral is in one phme and is usually
trichotomous, two branches arising opposite one another
from a joint of the main stem.

The conceptacles in this genus are in the form of promi-
nent swellings at the terminal extremities of some of the
branches, and the pore of each ripe conceptacle is at the apex
of this swelling.

Some of the conceptacles, however, are found not at the
extremity but at the sides of the joints.

The genus Corallina seems to be most abundant in the
temperate regions, being very common on the coasts of
Great Britain, France, and North America. It occurs in
great quantities in some localities in the Mediterranean
Sea, where Amphiroa is also found.

In former times this Coralline was collected, dried, and
sold in the shops for medical purposes, but it was not
considered to be so potent as the more expansive red coral.

The deposit of calcareous salts in the tissues of marine
Algae is not confined to the genera of the family Corallinaceae,
although it is in that family alone that we find the hard
massive growths that form a conspicuous feature of the
coral constituents of a coral reef.

It would take us far beyond the limits assigned to this
chapter if any attempt were made to describe and classify all
the calcareous Algae, but a short statement may be made
concerning one of the calcareous Red Algae which is extremely
abundant on some coral reefs and may serve as an example
of quite a different type of structure.

Family Chaetangiaceae. — The genus Galaxaura^ (Fig.
107) occurs in the Mediterranean and in the warmer seas of
the Indian, Pacific, and Atlantic Oceans, and it forms dense
clusters of profusely branching thalli attached to rocks and
corals by tuft -like roots of branching filaments. The
branches are usually cylindrical in form, and they are either
not segmented at all or, if segmented, the segments or joints
are not so pronounced or so regular as in Amphiroa or
CoraUina. The method of ramification, too, is quite different

' See F. R. Kjellnian, Kongl. SvcHska Vet. Handl. xxxiii. 1900.

CORAL ALGAE 209

from that of the other segmented coral Algae, being much
more profuse, not confined to one plane, and very irregular.
It is in the structure of the plant, however, as seen with a
lens, that Galaxaura differs from the other Algae that have
been described most conspicuously. When it is fresh or
preserved in spirit the branches show a smooth surface
without pores or markings of any kind, but when felt with a
needle or probe are found to be soft and yielding. When
dried the calcareous framework seems to collapse, leaving

Fig. 107. — Galaxaura. Nat. size.

only flattened shrivelled strands of granular chalky sub-
stance cemented together by the dried vegetable tissues.

Class Chlorophyceae

This large and heterogeneous group of the green sea-
weeds includes a few genera in which the thallus is strengthened
by the deposit of calcareous matter, and one of these — the
genus Halimeda — is so widely distributed in the tropical
seas and so abundant in many localities, that it must be
regarded as an important constituent of the coral reef flora.

Halimeda.^ — This plant consists of a short stem which

1 For a full account of this important genus see E. S. Barton, Siboga-
Expcditie, livr. 2, igoi.

210

CORALS

Fig. io8. — Halimeda opuntia
from Hulule Male, Indian Ocean.
Nat. size.

gives rise to a number of branches usually arranged in one
plane, and is attached to the sand in which it grows by a
mass of long branched iilaments.

The stem and branches are composed of a series of

calcareous internodes with un-
calciiied nodes, and are conse-
quently very flexible (Fig. io8).
The joints are frequently flat-
tened and may be round, circular,
kidney - shaped, triangular, or
cylindrical in form. The indi-
vidual plants vary a great deal
in size, but the majority of the
common varieties are not more
than a few inches in height.

In life these Algae are grass-
green in colour, but when dead
become white and break up into
coral-like beads or flakes.
In anatomical structure Halimeda is quite different from
the Lithothamnion group of corals and their allies, and the
principal differences can be easily recognised both in the
dried calcareous skeletal structures
and in the soft tissues, which can be
seen, with the help of a simple magnify-
ing glass, when the calcium carbonate
is dissolved away with acid.

If a dried internode be examined
it will be found to be rough to the
touch, not smooth and greasy like a
Lithothamnion, and it is so brittle that
it can be crushed between the finger
and thumb. With a lens the surface
is seen to be perforated by a number
of round pores about 0-014 mm. in diameter, regularly
arranged at equal distances apart (Fig. 109). In this
respect, therefore, although Halimeda is undoubtedly a
plant, it is not a Nullipore. When seen in section these
pores are found to be the mouths of short cylindrical

A*"

u '^ ^7 '' ^ J /\ ' n ^^^

^'^^

I 1» ■ t

I'iG. io(). — Surface view
of Halimeda opuntia when
dried, x 150 diains.

CORAL ALGAE 211

cups perforated at the base by a minute aperture
which brings them into communication with the labyrinth
of spaces in the calcareous matrix of the internodes. The
surface pores are therefore continuous with tubes of a lesser
diameter which penetrate to the middle of the internodes.
This is a feature of some importance, as it is unlike anything
that is found in the calcareous structures of animal corals.

When a piece of fresh or preserved Halimeda is placed
in a weak acid and the calcareous matter dissolved, the
substance of the plant that remains is found to consist of
a bundle of long tubes, sending off a number of branches to
the periphery of the internodes and continued into suc-
cessive joints through the soft uncalcified nodes. The fine
branches of these tubes terminate in swollen cylindrical
extremities which are arranged parallel with one another,
vertical to the surface, and fit into cups of the calcareous
skeleton previously described.

These terminal swellings of the branches are usually
called the " peripheral cells " although the term " cells "
is technically inaccurate, for Halimeda and its allies are not
strictly cellular Algae, the filaments or tubes of which they
are composed being continuous and not broken up by
numerous cell walls into cell units. Whether we should
call these Algae " non-cellular " or " unicellular," or adopt
an altogether distinctive term, is a matter of controversy
that can be safely left in the hands of the botanists.

The characters of Halimeda that have been described
are sufficient to justify the separation of the genus from
the Lithothamnion group.

It belongs to the group of the Chlorophyceae or Green
Seaweeds and to the family Codiaceae.

The genus Halimeda is widely distributed in the tropical
seas of the West Indies, Indian Ocean, and Pacific Ocean,
but also occurs in the Mediterranean Sea and south of the
Tropics, on the west coast of Australia, and the east coast
of Africa.

The most widely distributed species is the Halimeda
tuna, the original Opuntia marina or Corallina opuntia of
the earlier writers. It is the common species of the

212 CORALS

Mediterranean Sea, but is also found in shallow water in
many parts of the Tropics. Being a green plant and there-
fore dependent upon direct sunlight, as are all the Algae,
it cannot live in very deep water. Gardiner found it alive
at a depth of 55 fathoms in the Indian Ocean — not far
from the extreme limit of its bathymetrical distribution ;
but as it is comparatively light in texture and easily broken
up by wave action, the dead fragments and isolated joints
are frequently washed away into deep water and form there
an important constituent of the sea-bottom. Thus Darwin ^
states that, off Keeling Island, at a greater depth than
90 fathoms the bottom was thickly strewed with joints of
Halimeda.

But it is in the shallow waters of the lagoons, or among
branches of coral on the reefs protected from the rough
and tumble of the breakers, that Halimeda principally
flourishes and adds its quota to the calcareous deposits
of the tropical seas.

Two other genera of calcareous Algae belonging to the
same family may be mentioned.

Penicillus is a beautiful little coralline Alga from one
to four inches in height consisting of a cylindrical stem,
attached below to the mud and sand in which it grows by
a fibrous root mass, and terminating in a brush-like tuft
of free filaments. The shape of this plant has led to the
popular name for it of " the Merman's shaving brush." The
genus seems to be widely distributed in the tropical seas,
but very common in certain localities in the West Indies.

Tydemannia has only recently been described from
shallow water in the Malay Archipelago and Indian Ocean.
It is a remarkably interesting little form consisting of a
moniliform stem and branches, dividing up into a complex of
twisted tufts or groups of fan-shaped branchlets terminating
in long cylindrical filaments.^

' C. Darwin, Coral Reefs, p. 117.

- For further information on these genera and other calcareous
Codiaceae see A. and E. Gepp, Codiaceae of the Sihoga Expedition, livr. Ivi.,
1911.

CHAPTER XI

CORAL REEFS

" There is a great quantity of a kind of white coral on the shore,
between Galle and Matura and many other coasts in the Indies. . . .
There are large banks of this coral ; it is porous, neither so firm or
smooth as the upright which grows in small branches ; and when
they are come to the full growth, there grow others between them
and then upon these grow others till it is become like a rock for
thickness." — Mr. Strachan, Phil. Trans. Roy. Soc. vol. xxiii., 1702,
abridged edition, p. 711.

It is not surprising that the coral reefs of the tropical seas
have arrested the attention and excited the interest of
navigators and travellers of every generation. The white
rollers breaking on the barrier of corals and the calm, pale
blue water of the lagoon were emblems both of danger and
of safety to the earlier navigators ; the abundance and
variety of animal and vegetable life which the naturahst
saw through the clear water as he passed over the shoals
in his boat promised surpassing richness for his collections ;
and the brilliancy of the colours of the coral polyps and of
the varied fauna and flora associated with them was an
ever-recurring delight to any one endowed with a sense of
beauty in Nature.

But that is not all ; for, as the facts became known,
many questions arose in the minds of the philosophers as
to the origin of these reefs and the meaning of their many
physical peculiarities ; and it soon became clear that the
answers to these questions could only be given by the
solution of problems of absorbing interest but of extreme
perplexity and difficulty.

213

214 CORALS

In the study <>f coral reefs we have a series of natural
phenomena and a number of biological and geological
problems which could only be dealt with adequately in a
separate volume or series of volumes. But an outline
sketch of them must be attempted here because they
represent one of the principal objectives to which the study
of the several classes of corals inevitably leads.

We may look upon the Madrepores and the Millepores,
the Nullipores and the Astraeids, and even the Gorgonias
and the Foraminifera, as the bricks and mortar with which
the great mansions of the coral reefs are built ; and our task
is not complete if, having studied the bricks and mortar,
we do not consider the structure of the house as a whole.
Moreover, the coral reefs, like mansions, are inhabited, and
the study of the inhabitants — the fish, prawns, starfish,
worms, and many others — and their relation to the structure
which they frequent, cannot be entirely neglected even in
an introductory chapter on the greater subject.

It may be remembered that, although the structures
known as coral reefs are confined to the w'aters of the
tropical belt, the corals have an almost world-wide dis-
tribution in the sea. Many examples of corals found within
the British area have been described. Tangled masses of
coral of great size are dredged up from some localities of
the Mediterranean Sea. The cold waters of the Norwegian
fjords yield a harvest of large massive corals of various
kinds, and in the great depths of the ocean where the
temperature is little above freezing-point, corals are often
found.

But these corals occur usually as isolated individuals
or in relatively small patches, and it is only under the
tropical conditions of warmer water and more intense
sunlight that " when they are come to their full growth
there grow others between them and then upon these grow
others till it is become like a rock for thickness."

The coral reefs are as varied in their contours, in their
composition, and in their distribution as the dry land itself,
and the customary classification of them into fringing reefs,
barrier reefs, and atolls is nothing but an artificial aid to

CORAL REEFS 215

description and does not represent any sharp distinctions in
Nature.

But when a reef is situated only a few score of yards
from the shore, and separated from it at low tide by sand-
banks and boat channels, it is called a " Fringing reef."
When the reef is a mile or more from the coast-line and
separated from it by a lagoon with a few fathoms of water
at low tide, it is called a " Barrier reef." An atoll is a
circular, oval, or more irregular shaped island or chain of
islands in the open ocean composed of recent coralline lime-
stone raised a few feet above the level of the sea at high tide
and fringed on the outer side with coral reefs.

There are many intermediate forms between these three
varieties. Thus a fringing reef at one part of a coast-line
may be continuous with a barrier reef further along the
coast, and it would be difficult to say at exactly what spot
the one type merges into the other.

In the Paciiic Ocean there are many examples of more
or less conical islands surrounded by a barrier reef ; there
are cases of a very small central island surrounded by an
atoll-like barrier reef, and then there are the more typical
atolls without a central island. There is evidently in Nature
a complete series of these forms, and there is no sharp
distinction in type between a small island with a barrier
reef and an atoll. There are also many different kinds of
atolls. There is the typical ring-shaped island with a
central shallow lagoon ; there is the ring-shaped island with
one or more breaks in it, through which the tides rush back-
wards and forwards from the lagoon to the open ocean.
There are the half-ring or quarter-ring atolls with a group
of reefs or islets representing the other parts of the atoll
awash at high tide. And then there are the huge banks in
the Indian Ocean, one hundred miles or more in length, as
seen in the Maldive and Laccadive Archipelagoes, which
present the appearance of an atoll of atolls, an enormous
ring of atolls enclosing an immense lagoon perched on the
edge of a submarine bank that rises from the deep water
of the ocean.

Each of these reefs consists of a great variety of living

2i6 CORALS

and dead ccjials, and supports a rich fauna of lish, Crustacea,
starfishes, and holothuria, sea-worms, and smaller inverte-
brate organisms, as well as a flora of seaweeds ; but no
two reefs seem to be exactly alike, and the complex of
natural forces that plays upon them leads to the abundance
of some kinds of corals on this reef and to their suppression
on that, to the richness and vigour of growing corals in
countless masses, or to the accumulation of quantities of
dead and decaying lumps of coral among a relatively few
surviving living ones.

The first impression of one coral reef may be that it
consists of nothing but huge shrubs of stag's-horn Madre-
pores, of another that it is all palmate Madrepores, of a third
that it is all Lithothamnion, although a closer examination
shows that many other kinds of coral occur among the
prevalent forms. In other places, however — and this seems
to be the case particularly on the fringing reefs — the corals
of different species are more evenly distributed, Madrepores,
Porites, Millepores, Seriatopores, and other kinds being all
mixed up together in such a way that it is difficult to say
that any one species is predominant.

With such variety in the composition of the living coral
reefs, any detailed account that may be given must be
regarded as the description of a particular part of a particular
reef and must not be considered applicable to the reefs in
any other district. It is perhaps one of the greatest charms
of coral reef work that it presents so much variety. As
the naturalist surveys the fringing reef of a coast, he finds
with every mile that he traverses a different grouping of the
species of corals ; he discovers new varieties here and there,
he sees different kinds of fish and holothurians, he may
even find abundance of some species which formerly he
thought to be rare.

And as with the details of composition, so with the general
effects. On some reefs he may be charmed with the richness
and variety of the colours, on others disappointed with the
almost uniform display of dull brown or dirty pink tones.

Coral reefs also differ very much from one another in
what may be called their vigour or vitalitv. In some

CORAL REEFS 217

places the reefs are built up almost entirely by living corals,
sponges, and other marine organisms ; there is not a space
large enough for a human foot that is not covered with
something alive. In other places, perhaps only a few miles
away, the living corals are separated by massive boulders
and smaller rocks and stones of dead and decaying coral,
and the reef is scored by numerous irregular channels in
which but few living things are to be found.

It is often very difficult to account for these differences
in the vigour of the reefs. The corals require for their
healthy growth certain conditions of temperature, light,
food supply, freedom from sediment, and so on, which are
difftcult to measure and estimate. If all these conditions
are favourable a healthy vigorous reef is the result, but if any
of them are unfavourable some of the species of corals die,
and perhaps in dying create other unfavourable conditions,
until the reef itself shows signs of decay.

It is important to bear in mind that the coral reefs,
unlike the rocks of the coasts of temperate climes, are liable
to comparatively rapid changes in form. They may for
many years continue to grow seawards, and then, owing to
a change in the set of the currents that sweep the coast, or to
some other cause, they decay and retreat backwards towards
the shore. It seems probable that a reef never remains
perfectly stationary. It is alwa3's slowly advancing or
retreating, and with every movement it makes it must affect
in some degree the set of the sea currents on the coast and
thus influence favourably or unfavourably the growth of the
corals further along the reef.

It is like a huge living pulsating organism slowly stretch-
ing out an arm here and withdrawing one there, in some
places showing youth and vigour, in others disease and death,
capable of withstanding the rough buffetings of storms and
surf and yet extremely sensitive to some of the slighter
changes of environmental conditions.

In the growth and decay of the reefs there are many
agencies at work both for the protection of the corals when
alive and for their rapid disintegration when dead.

When a coral reaches a certain size the living tissues are

2i8 CORALS

apt to die at the base, leaving the bare skeletal structures
exposed to the attacks of various boring and otherwise
destructive organisms. For a time they may be protected
from these attacks by the overgrowth of many different
kinds of encrusting animal and vegetable colonies.

Among these the most important, perhaps, are the hard
calcareous structures formed by the coral Algae, Litho-
thamnion and Lithophyllum, which form at first a thin
film covering the exposed parts and following its contours
like a crust, and then later growing beyond its support
to form a thallus of its own. It is often discovered, when
a large lump of coral is examined, that it consists of a
thick crust of one of these coral Algae covering a core of
some kind of Madrepore, as if the Madrepore had been
overwhelmed and smothered by the Lithothamnion. But
it is a question which has not been satisfactorily answered
whether there is really any real smothering process in the
production of these lumps. It seems to be most probable
that the encrusting Alga has simply followed the death of
the living tissues of its host from its base until when the
last polyp has died it completely surrounds and decently
entombs it by its further active growth.

The coral Algae not only protect the individual Madre-
porarian and other more delicate corals from the onset of
decay, but undoubtedly play an important part in welding
them together to resist the action of the surf ; and on many
reefs where the breakers fall with great force they form, as it
were, an advanced post of coral reef to protect and shelter
the ranks of the others in the outer waters of the lagoon.

The exposed base and stems of corals are also protected
by the growth of the pink discs of the Foraminifera, Poly-
trema, and Homotrema, by Cellepora and other Polyzoa, by
various kinds of encrusting Sponges, by Tunicata, and some-
times by masses of calcareous worm tubes.

On the other hand, the exposed base of the coral may be
attacked by several species of bivalve molluscs which bore
great cylindrical tubes through its substance, by cirripedes,
worms, sponges, and even filamentous Algae, which dissolve
the calcium carbonate and form lesser tubes and cavities for

CORAL REEFS

219

their shelter and protection. If in this struggle for existence
the organisms which attack the base of the coral get the
upper hand over those that protect it, the time soon comes
when a strong wave causes the perforated base to fracture,
the colony topples over and is cast up into the sand of the
lagoon, where it is smothered or gradually falls down the
outer slope of the reef into deep water, to form with its com-
panions in misfortune a talus on which the living coral reef
extends.

The broken bits of dead coral that are cast into the
lagoon may be further comminuted by the strong teeth of
many species of the coral reef fishes, by passing through the
alimentary canals of the holothurians and various kinds of
Sipunculid and Polychaet worms, and by the rolling action
of the surf, until, at last, they are driven on to the dry land
and contribute to the formation of those glistening white
beaches which are so characteristic of the tropical shores.

A recent discovery by Drew ^ has shown that there is yet
another element entering into the complex problems of the
disintegration of corals and the formation of calcareous
sands and muds, and that is the precipitation of amorphous
calcium carbonate by the action of the denitrifying bacteria
of the sea. In the Bahamas and Florida Keys large quanti-
ties of a chalky mud seem to be formed by this action, and
it can readily be understood that if such mud, together with
the corals and shells which it has covered, were raised above
the level of the sea, it might in time become consolidated to
form a hard rock similar to chalk or limestone. Further
investigation of this important action in the Pacific and
Indian Oceans will doubtless lead to important results.

The constant formation of sand and mud by the disin-
tegration of coral is an important factor in the determination
of the constitution of the reef. If it is washed away as soon
as it is formed the corals can thrive, but if, on the other hand,
it is deposited in the form of silt on any part of the living
reefs, the corals may be killed.

* G. H. Drew, " On the Precipitation of Calcium Carbonate in the
Sea by Marine Bacteria," Papers from the Tortugas Laboratory of the
Carnegie Institution of Washington, vol. v., 1914.

220 CORALS

There seems to be nothing more fatal to the growth of
corals than this deposit of silt. The delicate polyps have
some power of removing a few light foreign particles that
fall upon them, but a continuous shower of grains of sand or
mud hinders their powers of expansion, interferes with their
capacity to capture and ingest their food, and by shutting
off the light from the canal systems checks the photo-
synthetic action of the zoochlorellae. Any change in the
set of the tides and currents that drives the silt on to a
vigorous part of a reef, or causes stagnation and a fresh
deposit of silt elsewhere, may be regarded as among the most
destructive of the agents which check the growth of the reefs.

The study of the existing conditions on the reefs leads,
then, to the conclusion that, in addition to the great con-
structive factors of coral growth, there are also destructive
agencies at work which may check and destroy what has
been built up when environmental circumstances change.
There are probably no examples of homogeneous reefs that
have shown continuous progress for long periods of time.
The growth of a reef is a process of stages of active increase,
of comparative stability, and in some cases of considerable
reduction, the sequence and duration of these stages varying
enormously in different parts of the tropical world.

It has been shown that in the building of the tropical
reefs a great many varieties of corals take part. It is not
the work of one genus or of one order of corals. There are
perforate and imperforate Zoantharia, Millepores, Alcyonaria,
and coral Algae in varying proportions contributing their
quota to the formation of the great masses of coral rock. A
critical examination of these corals proves that they are
not the same as those found in more isolated patches in deep
water or in the Mediterranean Sea, the Norwegian fjords,
or other extra-tropical regions of the world.

It becomes a matter of some importance, therefore, in
the consideration of the problems of coral reef formation,
to collect the evidence that is available concerning the dis-
tribution in depth of those that can be roughly classified
as reef-building corals as distinct from those that do not
enter into the composition of the reefs.

CORAL REEFS 221

Darwin estimated that the greatest depth at which the
reef-building corals can flourish is between 20 and 30
fathoms, and he inferred from that estimate that the reefs
could not have been formed by up-growth from a stationary
sea-bottom of any considerable depth.

It is interesting to find that, as a result of the extensive
investigations of more recent times, Darwin's estimate is
confirmed and the conclusion is reached that reef-forming
corals do not flourish at greater depths than 25 fathoms.^
It is true that some genera such as Madrepora, Porites,
Millepora, Heliopora, have been found alive at depths of
35-50 fathoms of water, but the conditions at these greater
depths do not appear to be favourable to the formation
of luxurious plantations. Some forms such as Heliopora,
Millepora, and Goniopora are more frequently found in
depths of over 20 fathoms than others, such as the Seriato-
poridae, which are usually confined to quite shallow water,
but there seems to be no doubt that they all flourish most
abundantly in water of less than 25 fathoms.

The genus Dendrophyllia is one of the few reef-building
corals which appears to be rarely found in water of less than
20 fathoms and to flourish in depths of 20-50 fathoms, and
it is interesting that this genus is also one of the few corals
that occur not only in the tropical seas but extend into the
cooler waters of the Mediterranean Sea and Atlantic Ocean.

The coral Algae, Lithothamnion and Lithophyllum, which
play such an important part in the constitution of some reefs,
are sometimes left exposed at low tide even in the Tropics,
but are more usually found in shallow water down to a
depth of 40 fathoms - ; but unlike the typical reef-forming
corals, these plants have a world-wide distribution, occurring,
sometimes in great abundance, not only in tropical seas but
also in temperate and arctic waters.

The corals of the order Stylasterina have a much greater
range of distribution in depth than any of the true reef-

1 J. Stanley Gardiner, Fauna and Geography of the Maldive and Lacca-
dive Archipelagoes, vol. i. pt. 3.

^ Madame Weber van Bosse in Science of the Sea, edited by G. H.
Fowler, 1912, p. 152.

222 CORALS

forming corals, llie genera Distichopora and Stylaster,
for example, are not uncommonly found in quite shallow
pools at low tide in the Tropics, but species of Distichopora
are found at a depth of 100-260 fathoms in the Indian Ocean
and the West Indies, and species of Stylaster are found in
the Malay Archipelago in depths of 0-1038 fathoms.^ The
other genera of this Order are principally confined to deep
water.

The reason for the limited distribution of the more
important reef-forming corals cannot be determined with
certainty. It may be that their lateral distribution north
and south of the tropical zone is checked by the lower
temperature of the water, a minimum temperature of about
18° C. being necessary for their continued existence.

The range in depth may be determined by the power of
direct sunlight to penetrate sea-water. There can be no
doubt that the coral Algae are entirely dependent upon
sunlight for their continued vitality, and if a depth of 40
fathoms be taken as the maximum depth at which living
coral Algae are found, it will be found to agree with the
maximum depth at which effective rays of the sun can
penetrate sea-water. The other reef-forming corals are not,
perhaps, so entirely dependent on sunlight as the coral Algae
are, for they are provided with tentacles and other organs
for catching and digesting animal food ; but still, a majority
of them are also provided with the chlorophyll-bearing
zooxanthellae which require sunlight, and it is highly
probable that these corals do not flourish unless their animal
food is supplemented by the food supplied by the zooxan-
thellae. In support of this conclusion it may be pointed out
that the Stylasterina which are not provided with zooxan-
thellae are independent of the action of direct sunHght, and
extend from shallow water to the great depths of the ocean.

The rate at which corals grow has also an important
bearing on many of the problems connected with coral reefs.
On this point a great deal of interesting information has been
collected in recent years. By the measurement of corals
found on anchors and cables which were sunk at a known

^ Stylasterina of the Siboga Expedition, livr. xix., 1905.

CORAL REEFS 223

date, or of corals found in channels that had been cleared a
definite number of years before, and by the measurement of
actual specimens on the reefs after an interval of years, we
are now in possession of some information which enables us
to judge of the rate of the growth of corals in shallow water.
Thus the branches of a Madrepore may grow at the rate
of 1-2 inches in length in a year, and a great mass of
Porites was found to have increased 30 inches in diameter
in 23 years at the rate of nearly 2 inches per annum.
There is probably ver}^ little uniformity in growth, the rate
varying a great deal according to temperature, food supply,
and many other natural conditions ; but it has been esti-
mated that under ordinary circumstances a reef might grow
upwards from a shallow sea-bottom at a rate of one foot
in ii| years, or 14I fathoms in 1000 years. ^

From the study of these general aspects of the recent
coral reefs we may now pass on to the consideration of the
greater geological problems of the origin of the atolls and
of the various theories that have been advanced in the
endeavour to solve them. The first serious attempt in this
direction was made when Darwin ^ published his famous
book on coral reefs, giving the results of his researches and
reflections on the subject during the voyage round the world
of H.M.S. Beagle. According to his theory all atolls and
barrier reefs of the world originated as fringing reefs in shallow
water off the coasts of tropical continental lands and islands.
When the land subsided by earth movements and the shores
became submerged the coral reefs, rising vertically as their
supporting rocks sank, became separated from the retreating
shore by ever-increasing distances. In this way the fringing
reefs became converted into barrier reefs and the shallow
sand-patched lagoons of the fringing reefs became deep-water
areas. In the case of islands, if the land continued to sub-
side until the island became entirely submerged, all that would

^ For further information on these points see : J. Stanley Gardiner,
Fauna and Geog. Maldive and Laccadive Archipelagoes, vol. i. Appendix A ;
and A. G. Mayer, " Ecology of Murray Island," Carnegie Institute of
Washington Publications, vol. ix., 1918.

- C. Darwin, Coral Reefs, ist ed., 1842 ; 3rd ed. edited by Prof. Bonncy,
1889.

224 CORALS

be left at the surface would be a ring of coral reef enclosing
a deep-water lagoon.

The Darwinian theory is usually called the subsidence
theory, because it postulates a gradual sinking of the crust
of the earth over wide areas of the great ocean basins.

Since the time when Darwin wrote, a great many more
facts have been ascertained concerning the character of the
floor of the great oceans, on the structure and distribution of
the upraised coral reefs of the tropical islands, and on the
construction and topography of living coral reefs and atolls ;
and many subsequent writers have expressed grave doubts
that the subsidence theory is not sufficient to account for
the occurrence of all barrier reefs and all atolls. Some
indeed, such as Alexander Agassiz, who spent many years
of his life in exploring and critically investigating the coral
reefs in all parts of the world, have come to the conclusion
that in no single instance can the presence of an atoll be
satisfactorily explained by the subsidence theory.^

It is possible that the truth lies between the two extreme
views, and that some barrier reefs and atolls have been
formed during subsidence and that others have been formed
during long periods of quiescence or even independently of
earth movements. Let us, then, consider very briefly some
reasons which have been brought forward as arguments
against complete acceptance of Darwin's hypothesis.

The discovery of great masses of coral reef situated
several hundred feet above the sea-level, composed of the
same genera of coral as now occur on modern reefs, on islands
in the Pacific Ocean situated in close proximity to true
barrier reefs, proves that this land has been actually elevated
in geologically recent times, and it is difficult to reconcile this
fact of elevation with a theory which demands long-con-
tinued subsidence in the formation of the neighbouring
barrier reefs. Many of the typical atolls of the Indian Ocean
are raised to a height of nine or ten feet above high-water

^ Prof. W. M. Davis of Harvard L'niv^ersity has recently given reasons
for believing that the subsidence theory is sufficient to account for the
occurrence of all atolls and barrier reefs (The Scientific Moutltly, vol. ii.
No. 4, 1916, and other publications).

CORAL REEFS 225

mark. This was well known to Darwin, who accounted for
it bv the supposition that the dry land of the atolls had been
formed bv boulders of coral cast up by the waves in great
storms. But if it had been formed in this way, the corals
of which it is composed would be found lying in various
positions, some upright, some on their sides, and some upside
down. A critical examination, however, of some of these
rocks has shown that the corals are all upright and in the
position in which they grew on the living reef. This proves
that even in the Indian Ocean, which was considered to
provide the most conclusive evidence in favour of the sub-
sidence theory, a recent elevation of a few feet has actually
taken place.

The question of the foundation on which the atolls and
barrier reefs rest is obviously an important one, and various
attempts have been made to answer it by making deep bore
holes through the coral rock.

Darwin considered that the many widely scattered atolls
must rest on rockv bases, ^ and if it could be proved by boring
that the atolls and barrier reefs do rest on rocky bases we
should be in possession of the most conclusive evidence of
the truth of the subsidence theory. But it has been shown
that in very manv cases the reefs rest not on a terrigenous
base but upon a submerged platform composed of a hard
limestone formed by calcareous organisms other than reef-
building corals, which has been planed down by wave
action in prehistoric times to a moderately level surface.

Sluiter ^ showed many years ago how it is possible for a
coral reef to be formed even on the soft volcanic mud of the
submerged slopes of Krakatoa, and borings through the coral
islands Edam and Onrust led to the discovery that they rest
on the muddy bottom of the Java Sea.

There seems to be, in fact, no direct evidence either from
borings or soundings, or by the study of elevated reefs, of the
existence of great thicknesses of coral rock, formed by the
typical reef-building corals resting on a land foundation such
as the Darwin theory of subsidence demands.

^ Darwin, C, Coral Reefs, 3rd ed., p. 125.
- Sluiter, Biol. Centralblatt, ix. 1S90, p. 738.

226 CORALS

There is still another difficulty in tlie way of accepting
the original form of the subsidence theory. The lagoons of
the atolls and barrier reefs are not deep pits or troughs, but
usually extraordinarily fiat basins at a more or less uniform
depth of twenty fathoms. If these reefs had been formed
over long periods of time by gradual subsidence of a few
thousands of feet, the lagoons would have been of greater
depth and provided with sloping sides.

To meet some of these difficulties Sir John Murray ^
put forward an alternative theory which did not involve
the hypothesis of a long-continued subsidence of the land.
The discoveries made during the voyage of H. M.S. Challenger
concerning the constitution of the floor of the great oceans
and the nature of deposits on the sea-bottom, led him to the
conclusion that a continuous rain of calcareous organisms
from the surface-waters causes the formation of submarine
banks, which from time to time rise to the level at which
reef-building corals can thrive. \Mien the plantations thus
started reach the surface of the sea by upward growth they
gradually assume an atoll form by the death of the corals
in the centre and the outward growth, like a fairy ring, of
the corals on the edge, the lagoon being formed subsequently
bv solution of the dead coral by the sea-water which per-
colates through the mass.

The barrier reefs are formed according to this theory by
the outward growth of fringing reefs on a basis formed
mainly by the talus of dead corals which are broken off
the growing edge bv storms, and the lagoon channels are
formed in the same way, by solution, as the lagoon of the
atolls.

This theorv, of which only the briefest outline can be
given here, has been very unfairly termed the " still stand "
theory. It is true that it would account for the formation
of the characteristic coral reefs on a perfectly stationary
foundation ; but Sir John Murray was fully aware of the
probability of earth-movements both of elevation and sub-
sidence, and his theory w^ould hold good notwithstanding
slow movements of this kind in either direction.

• Sir Jolm Murreiy, Proc. Roy. Soc. Ediu., \o\. x., 1S79-S0.

CORAL REEFS 227

Murray's explanation of the formation of the deep lagoons
by solution seems to be the least acceptable part of his theory,
as it has been shown that in the coral seas the water does
not contain free carbonic acid and there is definite evidence
that in many instances the lagoons are slowly silting up
instead of deepening, as they should do if they are subject
to solution. Notwithstanding these objections, however, it
is still possible that some of the lagoons have been formed,
not perhaps by solution but by the scouring action of the
tides, which do carry great quantities of the fine detritus
formed by the natural disintegration of the corals through
the channels into the deep water beyond the outer edge
of the reefs.

There are two processes going on continuously in the
lagoons, the accumulation of silt and the scouring action of
the tides, and these, in general, counteract one another ; but
it is probable that under changing conditions accumulations
may at one time gain the upper hand and at another the
scouring action may become dominant. The evidence that
a particular lagoon is at the present day silting up, is, at
any rate, no decisive proof that the lagoon has not formerlv
undergone a process of deepening by the scouring action of
the tides.

The existence in many parts of the world of extensive
submarine banks or platforms on which the modern coral
reefs rest has been the basis of another theory of coral reef
formation which has met with some support.

In the consideration of previous theories the question of
any possible changes in the sea-level does not necessarily
arise ; but it is clear that if the crust of the earth remained
stationary and the level of the seas rose, the coral reefs and
atolls might have been formed in precisely the same way
as if the crust of the earth subsided and the sea-level
remained constant.

It has been suggested ^ that during the Glacial Period so
much water was piled up on the continental lands in the
form of ice, that the level of the sea was lowered to the

1 See R. A. Daly, " The Glacial Control Theory," Proc. Amevican
Acad. Arts and Sci., \'ol. 51, 1915.

228 CORALS

extent of about 30 fathoms. By this means large areas of
sea-bottom were exposed which hardened to form hmestones
of varying constitution. As the ice melted and the sea-
level rose these areas were again submerged and planed
down to form the submarine platforms upon which, sub-
sequently, the new coral reefs were formed.

If it could be definitely proved that during the Glacial
Period in the northern hemisphere there was so much more
water stored up in the form of glacial ice than there is at
the present day as to cause a fall in the sea-level of 30
fathoms, there would be some foundation for this theory.
But the evidence on that point appears to be far from
conclusive. Moreover, the theory also demands that the
submarine platforms on which the coral reefs rest should all
be of the same (pleistocene) geological age, and evidence
bearing on this point can only be obtained by the study of
the foundations of reefs that have grown and subsequently
been raised above the sea-level since that period. It may be
some years before a sufficient survey of these upraised reefs
in many parts of the world has been made to judge fairly of
the evidence they afford on the glacial control theory, but
Wayland Vaughan has shown that the great Florida plateau
has existed since late Eocene times and that some of the
West Indian platforms are at least as old.^

The glacial control theory is extremely interesting and
ingenious, but it does not appear to be likely to supersede
entirely the other theories that have been briefly described.
It may be proved that " glacial control " had some effect
in producing the general structure and distribution of many
of the modern and recently upraised reefs, but there can be
little doubt that some of our modern reefs do not rest on a
submarine platform formed in post-glacial times and that
others rest on platforms that were certainly pre-glacial.

The conclusion that must be reached after a careful
study of the literature bearing upon the subject is, that
there is no general agreement among men of science upon
any one theory of the origin of coral reefs. The controversy

' T. Wayland Vaughan, S))iitlisojiiiui histitidioii, Bull. 103, 1919. This
paper contains an admirable summary of coral reef theories.

CORAL REEFS 229

continues, and as with increasing knowledge the problems
concerned appear to become more and more complicated,
demanding more extended investigations of ever-increasing
diiliculty and expense, it is impossible that a complete set
of explanations of the phenomena will be discovered in our
generation.

It has been suggested by some of the bitter critics of
evolution that Darwin has been discredited by his theory of
coral reefs. Nothing could be more absurd. The simple
and beautiful theory which he expressed was the starting-
point of a great scientific movement and has led to the
discovery of an immense store of facts about the physical
geography of the tropical seas of the greatest interest and
importance. If it is borne in mind that at the time he
wrote his famous book on coral reefs and islands our know-
ledge was far less than it is now, his work stands out as a
model of scientific reasoning and inference.

The evidence afforded by the embayments of islands that
are surrounded by barrier reefs, by the unconformable
relation of elevated reefs to the rocks on which they rest,
and by other geological considerations, appears to support
the view that subsidence of the earth's crust in the coral
reef zone has occurred over even a wider area than Darwin
himself believed.

The doubts that have been expressed, as the result of
more recent investigations, that solution or scouring could
have produced lagoon depths of over 20 fathoms, appear to
have turned the scale of opinion in favour of Darwin's
explanation of these depths by subsidence.

The principal conclusion made by Darwin, which has not
been confirmed, and will probably be abandoned, is that the
reefs were formed by long-continued depression of the lands
on w'hich they rest, and are consequently, in some cases, a
few thousands of feet in thickness. There is no evidence
either from borings in modern reefs or from the study of
elevated reefs of the existence of such vast masses of con-
tinuously formed coral rock. It appears much more prob-
able that in most parts of the coral zone periods of subsi-
dence of relatively short duration have alternated with

230 CORALS

periods of cle\'ation, and that coral reef formation has been
stimulated, checked, or even stopped, in successive periods
of time.

If it is necessar}', then, to abandon a part of the theory
of coral reefs suggested by Darwin, or to agree that his
theory does not account for the formation of some reefs
which have been investigated since his time, there is no
reason whatever for rejecting the many interesting and im-
portant results of his investigations, or for under-estimating
the marvellous skill with which he marshalled his facts and
formulated his scientific conclusions.

CHAPTER XII

THE EARLY TRADE IN BLACK AND RED CORAL

"At this point I must pause in order to indulge in my instinct
for rambling." — De Ouixcey.

Red Coral

From time immemorial red coral has been regarded as an
article of commercial value not only on account of its
colour, lustre, and texture, but also on account of its supposed
mystical powers as a charm and as a medicament.

There can be no doubt that before the Christian era it
was used by the Greeks, the Persians, the Indians, the
Chinese, and by the Celtic races of Gaul, of Britain, and of
Ireland ; and it is also quite certain that all the red coral
that was used by these people in ancient times came to them
by trade from the Mediterranean Sea.

The red coral of commerce {Corallium nobile) has a very
limited distribution. It is not found on any of the coral
reefs of the world, and in dealing with the early history of
the trade in coral it is important to note that it has not yet
been discovered in the Red Sea, the Persian Gulf, or the
Indian Ocean. The principal fisheries of the red coral were
those of the southern coasts of France, of the coasts of
Corsica, Sardinia, and Sicily, and of the northern coasts of
Africa from Tunis to the Straits of Gibraltar. In quite
recent times there has been a small fishery of red coral off the
Cape Verde Islands in the North Atlantic Ocean, but it may
be said that the genuine red coral is confined to the Mediter-
ranean Sea and a few localities west of it in the Atlantic.

Another kind of coral belonging to the same genus but to

232 CORALS

different species has been found in abundance in certain
waters off the coast of Japan, and, although this coral is some-
times red and is always of the same hard texture as the
Mediterranean red coral, so that it can be and is used for
ornamental purposes, the evidence seems to be quite con-
clusive that it was not exported from Japan until quite
recent times.

There can be little doubt, therefore, that the early trade
in red coral began in the Mediterranean Sea, and in all
probability in the western part of it, and that it spread from
there to the distant parts of the world, where it was prized
by the natives.

From the earliest times of which we have any record,
red coral was supposed to possess certain magical properties,
and was used not only for ornamental and decorative pur-
poses but to ward off evils of various kinds, to still tempests,
and to cure diseases.

The mythical origin of red coral is related in a poem by
Orpheus of Thrace and by Ovid,^ and may be briefly stated
as follows.

When Perseus cut off the head of the Medusa and cast it
on the sea-shore, the water-nymphs threw small branches of
seaweed at it just for the fun of seeing them turn into stone.
The seeds of these twigs when returned to the water gave
rise to the coral, which even to this day turns into stone when
it comes in contact with the air, although it is soft so long as
it is still submerged.

Minerva was so pleased with the exploit of her brother
that she conferred upon coral a number of the most extra-
ordinary virtues.

She next endowed the plant with virtue strange

And to its kind a lasting influence lent

To guard mankind on toilsome journeys bent,

1 Ovid, Metam. iv. 747-753 :

At pelagi nymphae factum mirabile temptant
Pluribus in virgis, et idem contingere gaudent,
Seminaque ex illis iterant iactata per undas.
Nunc quoque curaliis eadem natura remansit,
Duritiam tacto capiant ut ab aere, quodque
Vimen in aequore erat, fiat super aequora saxum.

EARLY TRADE IN BLACK AND RED CORAL 233

Whether by land their weary way they keep,
Or brave in ships the terrors of the deep.^

It was given also the properties of an antidote to all
manner of stings, poisons, and enchantments, of a protector
of the crops from plagues of caterpillars, flies, and pests of
various kinds, and of a universal drug to cure the diseases of
mankind.

The belief in the properties thus conferred upon coral
by Minerva spread with the trade to the most distant parts
of the Old World, and persists among the peasants of many
countries, in one form or another, even to the present day.

We have very little information concerning the use of
coral by the Greeks, beyond the reference to it in the poem
by Orpheus. In recent excavations on the sites of ancient
Greek cities, no specimens of coral in ornaments have been
brought to light. In the Royal Albert Museum there is a
copy of a pair of earrings in each of which there is a large
bead of pink coral. These earrings were found in the Crimea
and are believed to be of Greek workmanship of the fourth
century B.C.

Minns '^ states that corals have been found in the tombs
of the ancient Scythians, and that it was the custom among
the Asiatic nomads to adorn the flanks of creatures in their
art work with blue stone or coral inlaid.

There can be little doubt, however, that both Greeks and
Romans used coral in ancient times in the form of amulets
of various kinds to ward off evils from children and to
protect adults from real or imaginary dangers. Pliny says :
" Haruspices religiosum coralli gestamen amoliendis peri-
culis arbitrantur ; et surculi infantiae alhgati tutelam habere
creduntur."

But neither the Greeks nor the Romans seem to have
valued coral as an article of jewellery or for inlaid decorative
work on swords, shields, breast-plates, or other objects in
the same way or to the same extent as the Oriental races
and the Celts, and thus it came about that a trade was estab-

1 From a translation of the poem by Orpheus of Thrace by C W.
King in The Natural History of Precious Stones and Gems, 1865.
- E. H. Minns, Scythians and Greeks, 1913, pp. 65 and 268.

234 CORALS

lished with these distant countries which consisted in an
exchange of red coral for emeralds, rubies, pearls, and other
articles more highly valued by the Mediterranean races. ^

The use of coral by the Jews in pre-Christian times may
be inferred from two references to it in the Bible.

The texts in the English Version are :

" No mention shall be made of coral, or of pearls : for the price
of wisdom is above rubies." — Job xxviii. i8.

" Syria was thy merchant by reason of the multitude of the wares
of thy making : they occupied in thy fairs with emeralds, purple,
and broidered work, and fine linen, and coral, and agate." — Ezekiel
xxvii. 1 6.

There has been some controversy among scholars about
the correct translation of the Hebrew word " Ramoth,"
which in the English Version is translated " coral." Most
of the authorities seem to agree that the word " Ramoth "
does mean coral of some kind ; there are differences of
opinion as to whether it means " red coral " or " black
coral."

Gesenius expressed the opinion that it means " black
coral," because the word " Peninim," which in the English
Version is translated " rubies," is apparently red coral, and
considered that this view is confirmed by Lamentations iv. 7,
in which the Nazarites are described as " more ruddy in
body than rubies " (Peninim, i.e. than red coral). This view
also seems to receive support from another consideration
of the texts.

In the verse from Ezekiel, coral {i.e. Hebrew Ramoth) is
associated with emeralds, purple, and broidered work, fine
linen, and agate, articles of trade that must have come from
the Far East, and according to some authorities the word
" Aram " is wrongly translated " Syria," but should be
" Edom," a port for transport from S. Arabia and India.
Now, red coral could not have been imported from India
or from any country south of Palestine, as it occurs only in
the Mediterranean Sea, but black coral might have been

' "In the same degree that people in our part of the world set a value
upon the pearls of India, do the people of India prize red coral " (Pliny,
xxxii. chap. 1 1).

EARLY TRADE IN BLACK AND RED CORAL 235

imported from any of the warmer waters of the Red Sea,
Persian Gulf, or Indian Ocean (see p. 132).

In the verse from Job as it is translated in the English
Version, it is difficult to see any reason why " iiibies "
should be specially selected for comparison with " wisdom."
But bearing in mind the multiple and marvellous magical
properties of red coral in addition to its beauty as a jewel,
the translation of the verse according to the views of Gesenius
may reveal a new meaning. It would read thus :

No mention shall be made of black coral or of pearls, for the price
of wisdom is above red coral.

The black coral and the pearls imported from the South
are here grouped together, and the more precious red coral
from the West stands by itself as a symbol of the most valu-
able of worldly possessions.

Apart from these references to coral in the Bible, we have
practically no information as to the use of coral by the
ancient Jews.

There is abundant evidence of trade in coral with the
Far East in times long before the dawn of the Christian era.

It seems probable that Persia was an important market
for coral, for Solinus, in his reference to the coral from the
Gulf of Genoa, says : " This substance according to Zoroaster
has a certain potency and in consequence anything that
comes from it is reckoned among health-giving things."

But the Persians not only used coral themselves but
passed it on to the races further East as an article of trade,
for in early Chinese annals it is stated that " coral is produced
in Persia, being considered by the people there as their most
precious jewel." ^

x\t the time of the Han dynasty, a century or more before
the Christian era,- the Chinese were already well acquainted
with coral as an ornament, and it was valued so highly that

1 B. Laufer, " Sino-Iranica," Field Museum of Nat. History, Chicago.
Publications No. 201, igig, p. 523.

^ According to Prof. Pelliot the earliest use of the word Shanhu {i.e.
coral) is in a poem written by a Chinese scholar, Sseuma Siang-JQ.u,-whct. _
must have died about 117 B.C. {Archives concernant I'Asie ovientale, tt9te,Q,f ■')' .^\
p. 145, footnote). •- "v ■,.--,;.- V--','--'^, .

12 S / ^^ ^^

236 CORALS

an expedition was sent to the Mediterranean Sea to investi-
gate and report upon the coral fishery.

In the course of the trade routes, whatever they may have
been in those early times, from the Mediterranean Sea to
China large quantities of coral were bought by various
Asiatic races of the countries through which it passed.

In the care of the thousand Buddhas, south of the Gobi
deserts, Sir Aurel Stein found a number of paintings on silk
in which red coral is clearly shown.

The references to coral among the treasures of Thibet
and India are of a much later date, but it is very probable
that it was valued by the inhabitants of those countries
quite as early in history as it was by the Chinese.

Marco Polo, who made his famous and adventurous
journey across the Asiatic continent in the thirteenth century,
said that the coral that comes from our part of the world has
a better sale in Keshimeer than in any other country. He
also tells us that red coral was held in high esteem in Thibet,
for the people delight to hang it round the necks of their
women and of their idols. ^

Even to this day coral necklaces are among the most
cherished possessions of the wealthy Thibetans and are
included among the sacred treasures of the monasteries of
that country.

In India generally it may be said that coral was widely
used for ornamental purposes, being found in ancient rings,
necklaces, and among the precious stones that adorned the
thrones. Tavernier (seventeenth century) says that the
common people wear it and use it as an ornament for the
neck and arms throughout Asia and principally towards the
North in the territories of the Great Mogul, and beyond them
in the mountains of the kingdoms of x^ssam and Bhutan.

It is possible that the belief in some of its magical pro-
perties may have gone with the red coral into the regions of
the Far East, as we find it recorded in the T'ang Annals as
an article in the Chinese Materia Medica of that period, and
in the time of the Manchu dynasty red coral was used as a

1 H. Yule, Cathav and the Way thither, Hakluyt Soc, vol. i., iS66,
P- 159-

EARLY TRADE IX BLACK AND RED CORAL 237

sacrifice on the altar of the Sun.^ On this point, however,
our knowledge is very scanty. All that we do know for
certain is that it was highly prized as an ornament by these
people.

In Japan, red coral has been used for inlaid artistic work
on medicine cases (Inro), netsukes, tassels, and sword hilts
for several centuries. It is generally believed that most of
this coral was imported, and the fact that the Japanese word
for coral, " Sango," so closely resembles the Chinese word
" Sanhu " or " Sangu " suggests that it may have passed
through the Chinese markets.

However, at an early period, coral of a different species
but of a similar quality as regards texture and colour was
discovered in the bay of Tosa ; but, according to Kitahara,^
the fishery was carried on in secret and consequently very
much restricted in output, because the Daimyo of Tosa was
afraid that the coral might be commandeered by the Shoguns.
In this connexion it is interesting to note that on some of the
ornamental designs of the seventeenth century a branch of
red coral is depicted in the hands or the net of a dwarf,
curly-haired, dark, and prognathic fisherman, obviously not
a native of Japan. This may have been designed to throw
the Shoguns off the scent of a native fishery, but there is just
a possibility that it has reference to another coral fishery
in some distant country of which all other evidence has been
lost.

It was not until the Meiji reform of 1868 that the pro-
hibition on the coral fishery was removed and an extensive
and lucrative export trade from Japan was developed.

The earliest reference that can be found on the use of
red coral by the natives of the Malay Archipelago is by
Rumphius, who wrote at the end of the seventeenth century.
He tells us that the red coral is called by the Malays " San-
hosu," a word which is remarkably like the Chinese " Sanhu "
and the Japanese " Sango," and therefore suggests that they

^ In the Paulus Aegineta, published by the Sydenham Society, it is stated
on the authority of a Dr. Ainshe that the Tamool practitioners prescribed
red coral, when calcined, in cases of diabetes and bleeding piles.

- Journ. Imp. Fisheries Bureau, Japan, xiii., 1904.

238 CORALS

obtained it originally from China or Japan. Rumphius,
however, who insists that it is not found native in Malayan
waters, declares that it was brought to the islands by the
Portuguese and other Europeans.

There are several later references to the use of coral
among the natives of these islands. Valentyn, for example,
states that a girdle made partly of glass and partly of gold
set with coral was included in the dowry of the daughter of
the chief d'Arras of the island of Siauw off N. Celebes in
1677. But in this case, as in others, in which the coral is not
more definitely described, it may be doubtful w^hether it is
the red coral of the Mediterranean or some form of black
coral.

All that can be said is that it is very improbable that the
natives of an island like Siauw, situated in a sea that abounds
in coral reefs, would regard black or any form of white coral
of such value as to be set as a jewel in a bridal girdle.

Very little is known about the early history of the Malay
islands, but the undoubted fact that three centuries ago
there was an import of red coral by European merchants
lends probability to the view that there was earlier trade
in it carried on by the Arabs, who brought with them the
beliefs in the efficacy of red coral as a charm and an antidote
to poison.

It would be interesting if some definite informatic.n
could be given as to the routes by which coral was carried in
early times from the Mediterranean Sea to the Far East.
The discovery of coral in earrings in the Crimea, supposed
to be of the fourth century B.C. workmanship, and of the use
of coral in inlaid design by the ancient Scythians, suggests
that there was an overland route by way of Russia, the
Caspian Sea, and Middle Asia.

Pezalotte, who wrote in the early part of the fourteenth
century, states that " stript coral, clean and fine coral,
middling and small " was sold in the Constantinople market,
and it was evidently carried from there by the merchants,
who travelled along various routes to the markets of the Far
East.i

^ H. Yule, Cathay and the Way tlUher, Hakluyt Soc, vol. i., p. 303.

EARLY TRADE IN BLACK AND RED CORAL 239

But there seem to have been at least two other routes in
early times. In the first century B.C. the Roman navigator
Hippalus discovered the sea route from Aden across the
Arabian Sea to the markets of India, by which the mercantile
ships were able to avoid conflict with the traders from the
Persian Gulf. The author of the Peripliis of the Erythraean
Sea, who wrote about a.d. 60, described this new sea route,
and told the merchants that there was a demand for coral
at Cana (S. Arabia), at Barbaricum (at the mouth of the
Indus), at Ozene ( = U]jain on the Malwa coast), and at
Bacare ( = Porakad on the Malabar coast) ; and it was
probably by this route that a great deal of coral passed by
way of the Ganges to Thibet and China.

But the fact that there was already a demand for coral
in these places in India at this period of history shows that
there must have been an earlier trade in it by another route.
This trade was probably conducted b}^ Moors and Arabs
from the fisheries of Morocco across Syria, through Mesopo-
tamia, and by way of the river Euphrates to the Persian
Gulf.

There are some reasons for believing that in early times
the Arab merchants carried on a trade with Africa from Aden
by way of an overland route to the LTpper Nile, and it is
probable that the demand for coral at Cana (in S. Arabia)
mentioned in the Pen'pliis was to some extent due to its value
as an article of trade with negro and negroid inhabitants of
that country. 1

The records of the history of the dark-skinned inhabitants
of the African continent begin in comparatively modern
times, and it is impossible to state even approximately
when the negroes first became acquainted with red coral.
All that can be said is that, judging from the value they set
upon it a few hundred years ago, when the records begin,

^ It might be expected that the words used by the different races for
coral might help in the determination of these trade routes, but so far as
I can judge they do not. The following is a list of the names I have been
able to collect : Latin, Corallium ; Arabic, Marjan, or a rarer word said
to be derived from the Persian, Bussadh ; Armenian, Bust ; Hebrew,
Peninim ; Sanskrit, Pravala ; Burmese, Tada ; Thibetan, Chiru, or, in
addressing the higher classes, Guchi ; Chinese, Shanhu ; Japanese, Sango ;
Malay, Sanhosu.

240 CORALS

it is probable that their trade in coral had a very early
origin.

Among the treasures of the kingdom of Benin on the
west coast there was found a remarkably fine fly-whisk,
composed of several strings of coral beads attached to a
handle which is itself a very large solid stem of red coral.
From the same and neighbouring states there were obtained
some curious network caps strung with coral beads. These
specimens may be seen in the British Museum. It is known
that there was an extensive trade in coral with Liberia by
the Portuguese in the fifteenth century, and these specimens
may have come in this way by sea from the Mediterranean.^

But coral is widely spread among the natives of North
Africa and is used partly as an ornament in the form of
necklaces of beads, but sometimes as a phallus or in some
special form as a protection from the evil eye."^ The wander-
ing tribes of Moors carried red coral with them on their
travels to " still the tempests and to enable them to cross
broad rivers in safety," and probably carried it also as an
article of barter with the natives across the desert.

It is impossible to say how long this trade has been
going on , but it would be no exaggeration of the facts to say
that it began before the Christian era.

Al-Muqadassi, who flourished about a.d. 980, states that
the red coral of commerce in his time came from an island
named Marsa-al-Kharaz, which was near Bona on the coast
of Algeria, and other writers in Arabic, such as Jaqut (1229)
and x\l-Taifashi (1242), refer to the same island as the
principal source of red coral.

There is one great civilisation of North Africa, however,
which seems never to have held coral in high esteem, and
that is the one of which we have perhaps the most complete
records from the earliest times, namely, the Egyptian.^ x\ll
through the many dynasties the wealthy Egyptians prided
themselves on their necklaces, scarabs, rings, and other kinds

' H. Johnson, Liberia, vol. i., igo6, p. 74.

- W. Hilton Simpson, Among the Hill Folk of Algeria, 1921, p. 79.
* The predynastic Egyptians used bits of the red Organ-pipe coral
(Tubipora, p. 116) as beads.

EARLY TRADE IN BLACK AND RED CORAL 241

of ornaments of precious stones. They used cornelian,
amethyst, garnet, turquoise, lapis-lazuU, and other precious
stones, but rarely, if ever, red coral.

We mav now consider the evidence of an early trade in
red coral in another group of countries. Some years ago a
great bronze shield was found in the bed of the river
Witham in Lincolnshire which bears five large pieces of
red coral, three arranged in a triangle in the centre and two
at the sides. Each piece is circular in outline and was ground
to form a convex surface and polished. This shield is sup-
posed to belong to the early Iron Age.

Armour decorated with coral in a similar way has also
been found in Ireland.

How did the Celts of Britain and Ireland in those early
days get their coral to ornament their arms ? The answer
to this question has been given by Reinach,^ who traces the
trade in coral from the Mediterranean Sea through Gaul to
the British Isles. So important does he consider this trade
to have been that he speaks of a " coral epoch " in the history
of the Ancient Gauls. He tells us it was used for ornament-
ing weapons of ceremony, shields, armour, fibulae, and other
things made of bronze, but rarely used on iron or gold. It
was also used as a medicine in various disorders.

This trade in coral, however, came to an end with the
Roman Conquest, for the Romans required all the coral
they could get for their trade with India by way of Alexandria
and the Red Sea as described in the Periplits. From that
time onwards red enamel seems to have been used by the
Celts as a substitute for coral.

It would be interesting to trace the history of the trade
in coral from the days of the Roman Empire to the present
time, but that is a task that must be left to the patience
and skill of the trained historian.

A few words may be said, however, about a series of
events in the sixteenth century which heralded an important
and critical epoch in the history of the coral fishery.

The later years of tlje Wars of the Crusaders had brought

^ S. Reinach, " Le Corail dans I'industrie celtique," Revue Celtique,
tome .XX., 1899.

1^2

CORALS

the European traders into touch with the commerce of the
East, and this led to an increased activity and interest in the
coral fisheries of the Mediterranean Sea. The Venetians,
Genoese, Corsicans, and Moors carried on the trade with the
various fluctuations of success that followed their struggles
for the supremacy of the sea.

It is probable that the fisheries in shallow water on the
north side of the Mediterranean Sea were already showing
signs of exhaustion and that envious eyes were cast on the
richer coral beds that were known to exist off the coasts of
Algeria and Morocco, but the dangers of
the voyage across the sea to waters infested
with pirates and controlled by a powerful
and hostile empire of Mohammedans held
in check this source of supply for the
Europeans of the North.

In the year 1535, however, an alliance
was concluded between the French and
the Turks with reference to the control of
the north coast of Africa, and this was
followed by the " Concessions d'Afrique "
by which, in 1580, a monopoly of the
coral fishery from Cape Roux to La
Sebouse was granted by Henri IIL of
France, with the consent of the Emperor
Soliman II., to a French trading compan3\
The first President of this company was
one Thomas Lenche, a Corsican by birth, but a naturalised
French citizen of Marseilles. Lenche made a large fortune
by his trade in coral, and he was succeeded by his son
and his grandson in the business, but in later years inter-
national disputes and warfare brought new difficulties and
made the monopoly far less profitable.^

The trade in coral has continued from medie\'al times
with various fluctuations to the present day, although many

1 The subsequent history of the company and of the battles of the
French for the command of the coral fishery on the north coast of Africa
is fully related in the works of P. Masson : " Les Compagnies du Corail,"
Annales de la Faculti des Lettres d'Aix, vol. i., 1907 ; Histoire des
elablissements et du commerce fraticais dans I'Afrique barbaresqiie, 1903.

Fig. 1 10. — Trade
mark of the First
Coral Company.
From ilasson.

EARLY TRADE IN BLACK AND RED CORAL 243

of the chief values attributed to coral have become discredited
by educated people. Red coral was widely used down to
the end of the eighteenth century not only in the form of
necklace beads and ornaments but also as a medicine. It
was used in the form of a powder and taken in wine or in
water for various disorders. John Parkinson, in his Theatre
of the Plants published in 1640, gives a long list of diseases
for which it is commended, such as consumption, the falling
sickness, gonorrhoea, sore gums, and ulcers in the mouth.
It is also said to cause an easy delivery at birth, and it is
much commended " agamst melancholly and sadnesse and
to refreshen and comfort the fainting spirits."

There are many prescriptions to be found in the pharma-
copoeias of the eighteenth century in which red coral is used
as an ingredient. The following example of such prescrip-
tions, taken from A Complete English Dispensatory by John
Ouincey, M.D., published in 1739, may be quoted :

It is called Piilvis purptireus and is described as a pretty
medicine for fevers in children, the measles, and smallpox.

"Take burnt hartshorn, white amber, red coral of each an
ounce ; crabs' eyes and claws of each two ounces ; saffron half
a scruple ; cochineal two scruples ; make them all into a paste,
after they are finely levigated with jelly of hartshorn, and form
it into little balls which dry and use."

Many other examples could be given to prove the value
attributed to red coral for medical purposes in the eighteenth
century, but white and black coral were also used although
they were not so highly esteemed as the red.

It is quite impossible to say exactly what genera or
species of white and of black coral are referred to, but it
is certain that the common little alga of our rock pools,
Corallina officinalis, was used for such purposes (p. 197).

Moliere made fun of the practice of giving precious
stones as drugs when in Le Medecin malgre lui he makes
Sganarelle prescribe for a patient " un fromage prepare, ou
il entre de I'or, du corail et des perles et quantite d'autres
choses precieuses." But it was not ridicule that killed the
use of coral in medicine, but the spread of knowledge of
chemistry and therapeutics. When it was realised that

R 2

244 CORALS

coral, when analysed, is found to consist of calcium carbonate
with traces of calcium sulphate, magnesium sulphate,
organic substances, and, in the case of red coral, a trace of
oxide of iron, and that its therapeutic value was no greater
than powdered chalk, it fell into disuse. In a Pharmacopoeia
of 1677 powdered red and white coral are catalogued ; in a
Pharmacopoeia of 1788 red coral only is mentioned ; and
in Pereira's famous Materia Medica of 1842 the only
statement that appears is that " coral is still sold in the
shops."

Reference has been made to the use of red coral bv
natives of North Africa as a phallus and as a protection
against the evil eye. It is said to be used for the same pur-
poses by the peasants of Italy and of other parts of South
Europe. The superstition that seems to have been most
persistent in this country is that it assists children in the
cutting of their teeth.

" It helpeth children to breed their teeth, their gums being
rubbed therewith ; and to that purpose they have it fasten
at the ends of their mantles." — Coles in .-f^n;;; and Eden, quoted
by Brand.

Fabritio. Art thou not breeding teeth. . . . I'll be thy nurse
and get a coral for thee and a fine ring of bells. — ^Beaumont and
Fletcher, The Captain, Act iii. so. 5 {ca. 1613).

From this superstition, undoubtedly of Roman origin,
is probably derived the custom still prevalent in manv
families in this country of decorating their young children
with a necklace of coral beads.

And thus there survives to the present day the last
relic of the virtues conferred upon coral by Minerva to
commemorate the victory of her brother Perseus over
the Medusa.

Black Coral

It has already been stated that according to some com-
mentators the Arabic word Ramoth, translated "coral " in
the English \'ersion of the Bible, probably meant " black
coral." There seems to be no doubt that some kind of black

EARLY TRADE IX BLACK AND RED CORAL 245

horny axis of a marine organism was used, from very early
times, as an ornament or as a talisman on account of the
magical properties attributed to it.

The uvmradi]^ of the ancient Greeks was, in all
probability, a kind of black coral, and was considered to be
of value as an antidote to the stings of scorpions and for
other medical and magical purposes.

According to some of the older writers the herb given by
Mercury to Ulysses as a charm to protect him from Circe
was a piece of Antipathes. Rumphius quotes Salmasius as
having written in his notes on Solinus that Antipathes was
used as a protection against sorcery. Pliny refers to it in
his alphabetical list of stones. He says, Book xxxvii. chap.
54, " Antipathes is black and not transparent : the mode of
testing for it is by boiling it in milk to which, if genuine, it
imparts an odour (?) like that of myrrh. The magicians also
assert that it possesses the power of counteracting fascina-
tions." Dioscorides regarded Antipathes as a kind of
black coral which was possessed of certain medical proper-
ties. The substance called Charitoblepharon, mentioned b}^
Pliny {Nat. Hist. xiii. 52), which was said to be particularly
efficacious as a love charm and to have been made into
bracelets and amulets, was probably some kind of black
coral.

These and other vague references to the substance by
ancient Greek and Roman authors do not, it is true, give us
any certain clue as to the identitv of their Antipathes, and
it is only by indirect circumstantial evidence that the con-
clusion is arrived at that it was the axis of one of two or
three kinds of marine flexible corals.

The word Antipathes has been handed down to us from
the Greeks, by the Roman writers Pliny and Solinus, and
by the naturalists of the sixteenth and seventeenth centuries
as the name of one of the flexible corals with a black horny
axis. In modern systematic zoology it is the name of one
genus of the Antipatharia. It does not follow, however,
that what we call Antipathes to-day is the same thing
as the Antipathes of the Greeks and Romans. In fact,
it is almost certain that the ancient writers would have

246 CORALS

called anything of the nature of a black hornv axis
Antipathes, whether it was Antipathes, Gerardia, Plexaura,
or Gorgonia.

Pliny's milk test for Antipathes is interesting but unfor-
tunately very obscure. The phrase he uses is " experimen-
tum eius, ut coquatur in lacte ; facit enim id murrae simile."
But similar to myrrh in what respect ? In odour, in colour,
or in form ? Solinus considers it to have been similar to
myrrh in odour {Collect, v. 26), but other authors have inter-
preted Pliny to mean similar to myrrh in colour. If this
test be applied to a piece of Antipathes it will be found,
after prolonged boiling in milk, to have a faint odour
resembling that of heated myrrh, but the colour of neither
the milk nor the coral seems to be in any way affected.
For this reason it seems probable that Pliny meant to say
" similar in odour to myrrh."

In modern times black coral is still in use in the form of
bracelets worn on the wrist or arm as a cure for rheumatism,
as a protection from drowning, and for other purposes of a
similar kind. Bracelets and other articles of the same
material are worn in China and Japan, in the Malay
Archipelago, and in the islands of the Indian Ocean ; and
there is reason to believe that the belief in its virtues
has been handed down by tradition from very ancient
times.

In his book on the Antiquities of the Jews (i. 3. 6),
Josephus relates that according to Berosus, the Chaldean,
there is still some part of Noah's Ark in Armenia, and the
natives carry off pieces of the bitumen (pitch ?) to make into
amulets for averting mischief. We have in this passage
reference to a substance like bitumen {i.e. black and flexible
when heated) which was believed to possess magical pro-
perties. Of course, it may not have been black coral at all,
but if black coral accompanied by the beliefs in its efficacy
against evils of many kinds was transported to distant parts
of the world, as we know red coral was transported at that
period, it would not be remarkable if it became associated
with the Noah's Ark myth.

It would be a matter of great interest if scholars learned

EARLY TRADE L\ BLACK AND RED CORAL 247

in Jewish antiquities could throw any further hght on the
use of either black or red coral by the Children of Israel in
early times.

The most complete account of this superstition in the
Malay Archipelago is to be found in Rumphius's Amboinsch
Kruidhock, xii. p. 195, published in 1750, in the article on
CoraUium nigrum or Accarbaar itam. He savs that the
natives make bracelets of it by soaking it in cocoanut oil
and bending it into the form required over a slow fire while
smearing it all the time with oil. It is then polished with a
rough leaf. Sometimes it is inlaid with gold or silver orna-
ments. It is sometimes made into sceptres for the chiefs,
and it is also made into a powder by grinding with a stone,
mixed with water and drunk as a medicine. It would take
too much space to give in detail the various diseases for
which black coral was used as a remedy ; but it is evident
that its virtue was not supposed to be confined to the cure
of rheumatism and other diseases, as it was used for ensuring
the healthy growth of children, and by adults for protection
against sorcery, and by the great chiefs as a symbol of dignity
or power.

There were other kinds of Accarbaar or Bastard corals
which were known to the Malays in the time of Rumphius
and used by them for medicinal purposes, but the Accarbaar
itam or CoraUiiim nigrum was regarded as the most important
and was held in the highest esteem. Among these was the
Accarbaar puti, which, from the figure given by Rumphius,
was an Alcyonarian belonging to the family Isidae and
probably to the type genus Isis. This is of some special
interest, as the Mediterranean species of Isis was held in
high esteem by the Mediterranean races in classical times
and was currently believed to represent the petrified hair
of Isis. But that is another story, and one about which
only the most fragmentary indications remain.

The task of identifying the various kinds of black coral
mentioned by the ancient and subsequent writers up to the
end of the eighteenth century is an extremely difficult one,
as detailed descriptions of the characters upon which the
modern classification is based are almost entirely lacking.

248 CORALS

The substance was evidently black or dark brown in colour ;
it was capable of being bent or twisted when subjected to
heat and it was hard enough to be given a polished surface.
Moreover, it may be presumed from various references that
it was a product of the sea.

It might therefore have been the Keratin axis of one of
the Ple.xauridae, of one of the Gorgonidae, or of one of the
Antipatharia, or finalh' of Gerardia savalia.

The Accarhaar Ham of Rumphius was probably a Plex-
aurid. The figure of the stript coral that Rumphius gives is
not conclusive, but quite consistent with this identification.
In the description of the coenenchym, which covers the axis
when it is fresh, he uses the Dutch word " Schorse," i.e.
bark, whereas in the description of another Accarbaar,
which is almost certainly a Gorgonid, he uses the word
" Korste," i.e. crust. In the description of a third Accarbaar,
which is obviously an Antipatharian, he uses the word
" Slijm," i.e. mucus. With such an accurate observer as
Rumphius was, we may assume that the use of these different
words for the coenenchym signified a real difference in
character between them. In the Plexauridae the coenen-
chym is relatively thick, in the Gorgonidae it is almost
invariably thinner, whereas in the Antipatharian it is
usually little more than a soft and delicate covering of
the axis.

Rumphius states that the Accarhaar itam is not identical
with Pliny's Antipathes because it does not give the smell
or colour of myrrh on boiling in milk. For other reasons
than this, however, we may feel certain that the Antipathes
of Pliny and the earlier writers w^as not a Plexaurid. The
evidence seems to point to the conclusion that the black
coral commonly used by the ancients was the form mentioned
by Imperato (1599) as Savaglia and now known as Gerardia
savalia. (Until quite recently Gerardia was considered to
be an Antipatharian, but it has now been definitely placed
in the order Zoanthidea.) The reason for believing that it
was Gerardia is that this coral grows in the Mediterranean
Sea, whilst the Plexauridae do not, that it attains to great
dimensions (a great specimen in the British Museum being

EARLY TRADE IN BLACK AND RED CORAL 249

two metres in height and spreading fan-wise to a width of
over two metres) , and the surface of the branches is smooth
and devoid of spines. It is possible that in addition to the
Gerardia the main stem of some of the species of Antipatharia
that are found in the Mediterranean Sea may also have been
used. Gansius in his Historia coralliorum (1666) describes
a species, Antipathes hirsutum, found in the Sardinian Seas,
which is in length greater than the human stature. The
axis of such a specimen if polished would be difficult to
distinguish from that of Gerardia.

The difficulty of determining the black coral of the
ancients, however, is due to the possibility that they may
have imported it from the South, in which case Plexaurid
or Gorgonid coral may also have come into use. Thus Pliny
says in writing on coral, Nat. Hist, xxxii. 11, " gignitur et
in Rubro quidem mari sed nigrius item in Persico — vocatur
lace — laudatissimum {i.e. red coral) in Gallico sinu circa
Stoechades insulas, etc." This passage indicates that the
most valuable kind of coral known to the Romans came from
the Isles D'Hyeres and other places in the Mediterranean
Sea, but a black kind was also imported from the Red Sea
and the Persian Gulf in which the Cor allium nobile is not
found .

Black coral was also known to the Moors in early
times, and was very probably obtained by the fishermen
engaged in the famous red coral fishery off Marsa-al-
Kharaz, the modern Bona or Bone on the coast of Algeria.
The Arabic name for black coral was " yasz " or " yusz," a
word which seems to have some resemblance to Pliny's word
" jace."

These few notes on the use of black coral in early times
may seem to be very fragmentary and inconclusive, but
they may be perhaps sufficient to create some interest in and
to stimulate further investigation in a chapter of zoological
mythology which has not yet been written. It is probable
that classical and Oriental research will reveal a great many
more references to this substance than are recorded in these
notes, and it may be expected that the excavations of the
antiquaries will bring to our collections some specimens of

250 CORALS

black coral that were used in ancient times ; but there is
sufficient evidence to prove that the belief in the magical
properties of black coral is not only widespread at the
present day, but carries with it the sanction of a tradition
which has been transmitted from the early days of our
Western civilisation.

INDEX

Figures in thick type indicate the page on which the genus or species is described
in its systematic position; f . = and in following pages; (fig.) = the page on
which an illustration of the genus or species will be found other than in its
systematic position.

Accarbaar itatii, 132, 247, 248

Accarbaar piiti, 247

Acropora, 90

Adeona, 166

Adeonella, 166

Agaricia, 74

Agassiz, A., 145, 224

Alcyonacea, 135

Alcyonarian corals, 103 f.

Alcyonarian polyp diagrams, 109

(figs.)
Alcyonarian structure diagram, 104

(fig-)
Alcyonium, 103
Alcyonium maniis marina, 103
Algae, 19. 197 f.
AUopora, 153, 156
Allopora nobilis, 134
Al-Muqadassi, 240
AI-Taifashi, 240
Amphihelia, 42, 44 (fig.)
Amphiroa, 206
Amphiroa calif or >iica, 206
Ampullae, 146, 150, 151
Anacropora, 97
Annelid worm tubes, 192
Antheridia, 204
Anthocaulus, 68
Anthocyathus, 68
Antipates, 136
Antipatharia, 136 f., 248
Antipatharian corals, 136 f.
Antipathes, 138, 245
Antipathes flabellitm, 140
Antipathes hirsiitiim, 249
Antipathes larix, 138 (fig.), 139

Antipathes spiralis, 140
Aphanipathes, 140
Archegonia, 204
Aspidosiphon, 39
Astraea, 51, 72
Astrsees armes, 47

inermes, 47
Astraeidae, 31, 46
Astraeidae simplices, 62
Astroides, 80
Astroides caliciilaris, 80
Astrosclera, 191
Astrosclera ivilleyaiia, 191
Astylus, 156
Atoll, 215

Autozooid, 8, 16, 104
Axifera, 135
Axis, of Antipatharia, 136

of Corallium, 109

of Gerardia, 142

of Gorgonacea, 120 f., 134
Axopora, 149

Bacteria, marine, 219
Baker, H., i, 157
Balanophyllia, 76
Balanophyllia regia, 26 (fig.).
Barrier reefs, 215
Barton, E. S., 209
Bastard corals, 247
Batu swangi, 116
Beaumont and Fletcher, 244
Bell, F. J., 98, 141
Bergson, 9

Black coral, iii, 234, 244
Blue coral, 118

252

CORALS

Boccone, 15
Boschma, H., 69
Bourne, G. C, 59
Boyle, 143
Brain coral, ^^
Brown, 90

Calcium carbonate, 17
Calices, 2S

Caligorgici iJabclluni, 131
Calyx, diagram of, 32 (fig.)

of Stylaster, 153
Carlgren, 141

Caryophyllia, 16 (fig.), 27 (fig.)
Caryophyllia siiii/hii, 26, 37, 76
Cavernularia, 1 1
Cell-corallines, 5
Cellaria, 172
Cellaria fistulosa, ijz
Cellepora, 168, 169 (fig.)
Ceilepora pumicosa, 170
Ceratopora, 133
Ceratoporella, 133, 134 (fig)
Ceratoporella Nicholsonii, 134
Cerithium, 39
Chaetangiaceae, 208
Charitoblepharon, 245
Cheilostomata, 164
Chlorophyceae, 19, 209
Chlorophyll, 20
Chrysogorgiidae, 133
Cirripathes spiralis, 140
Cladocora, 53, 61
Cladocova arbusciila, 61
Classification of corals, 20

of Alcyonaria, 135

of Madreporaria, 30

of Stylasterina, 156
Clusius, 129
Cnidaria, 18
Codiaceae, 211
Coelenterata, 18
Coenenchym, 16
Coenosarc, 30
Coenosarcal canals, 16, 148
Coenosteum, 28
Coenothecalia, 120, 135
Coles, 244
Columella, 26
Conceptacles, 200 (fig.), 204,

(fig)
Concessions d'Afrique, 242
Conopora, 156
Conosmilia, 102
Convergence, 161

205

Convoluta, 21

Coral, Asiatic names for, 239

bastard, 247

black. III, 2^4, 244

blue, 118

brain, 55

derivation of the word, 1

King, 120

moss, 207

mushroom, 63

organ-pipe, 112

prickle, 136

red or violet sugar, 152

Red King, 123

scarlet and gold star, 76

stag's horn, 91

sugar, 145
Coral reefs, '213 f.

theories of, zz}, I.

glacial control theory of, 227

" still-stand " theory of, 226

subsidence theory of, 224
Coralhna, 207

Corallina officinalis, 160, 207, 243
Covallina opiintia, 211
Corallinaceae, 199 f.
Coralline, 159

CoraUium, 105, 107, 108 (fig.)
Coy allium album, 2
CoraUium, articularum , 4
CoraUium nigrum, 4, 247
CoraUium nobile, i, 108, iro (fig.),

178, 231
CoraUium rubrum, no
CoraUium verrucosum, 2
Coralloides, 2
Corallum, 18
Corals, distribution in depth, 221

geographical distribution of, 214

rate of growth, zzz
Costae, 27
Couch, 167
Crab-gall, 84 (fig.)
Crisia, 160

Crisia eburnea, 160, 161 (fig)
Cryptohelia, 155, 156
Crypts, 190
Cycloseris, 67
Cyclostomata, 160
Cyclosystems, 146, 133, 154 (fig.)
Cystocarps, 204

Dactylopore, 146, 152, 153
Dactyloporidae, 198
Dactylozooids, 147, 150

INDEX

253

Dakin, 187

Daly, R. A., 227

Dana, 67, 70

Darwin, C, 212, 221, 223, 224

Dasycladiaceae, 198 f.

Davis, W. M., 224

Dendrophyllia, 78, 221

Dendrophyllia cornigera, 79

Dendrophyllia ramea, 78, 79, 90

Dendrophyllia willevi, 80

Desmophyllum, 40

Desmophyllum crista-galli, 40

Diaseris, 9, 69

Dichocoenia, 54

Dissepiments, 47, 48 (fig.)

Distichocyathus, 92

Distichopora, 151 (fig.), 152, 156,

Doderlein, 191

D'Orbigny, 177

Drew, G. H., 219

Duerden, J. E., ^^, 35, 53, 56, 59,

61. 7i. 74, 94. 95. 96. 149
Dujardin, 176, 177
Duncan, P. M., 31, loi

Echinomuricea, 105 (fig.)

Echinopora, 61

Ectoprocta, 159

Ectosepta, 36

Edge-zone, 59

Ehrenberg, 59, 81

Elephant ear, 97

Ellis, J., II, 12, 13, 69, 121, 197, 198

Ellis, J., and Solander, 115

Endopachys, 77

Endopachys grayi, 77 (fig.)

Endotheca, 47

Engler and Prantl, 205

Entoprocta, 159

Entosepta, 36

Epitheca, 27

Errina, 154, 155 (fig.), 156, 163

Erriiia aspera, 135 (fig.)

Eschar a retiforiins, 167

Eunicella, 126

Euphyllui, 57, 38 (fig.)

Eupsammiidae, 31, 75 f.

Eusmilia, 37

Ezekiel, 234

Fa via, 50, 31 (fig.)
Filograna, 193 f.

Filograiia implexa, 194 (fig.), 193
(fig)

Fission in Astraeid coral, 34, 34 (fig.)

in Astraeidae, 53

in Porites and Madrepora, 34,
35 (figs.)
Flabellum, 40
Flabelliiiii ntbruiii, 41 (fig.)
Flexible corals, 106
Flustra, 168
Food of Alillepora, 147
Foramina, 178
Foraminifera, 19, 176 f.
Foslie, 203, 203
Fringing reefs, 215
Fungia, 63, 65 (fig.)

young stalked form, 68 (fig.
Fungiidae, 31, 62

Galaxaura, 208

Galaxea, 48

Galaxea caespitosa, 49 (fig.)

Gamble and Keeble, 21

Gansius, 249

Gardiner, J. S., 183, 202, 212, 221,

Gasteropore, 146, 132, 153

Gasterozooids, 147, 130

Gepp, A. and E., 212

Gerardia, 141

Gerardia saralia, 141, 248

Gesenius, 234

Gesner, 2

Goniastraea, 53

Goniolithon, 203, 203

Goniopora, 96, 221

Gonophore, 131

Gorgonacea, 133

Gorgonellidae, 128

Gorgones, 124

Gorgonia, 103 (fig.), 124, 125 f.

Gorgonia carolini, 127

Gorgonia flabellum, 125

Gorgonia flamme a, 127

Gorgonia verrucosa, 126, 127 (fig.)

Gorgonidae, 248

Gosse, P. H., 76

Guynia annulata, 10 1

Gymnolaemata, 139, 160

Crypsina, 180, 184

Gypsina plana, 183, 186

Haddon, A. C, i 73
Hair of Isis, 123
Halimeda, 209
Halinieda opun/ia, 210, 211
Halomitra, 69

254

CORALS

Hapalocarcinus, 84

Haploscleridae, 190

Harmcr, S. F., 173

Haswellia, 175

Heliastraea, 51

Heliolites, 120

Heliopora, 103, 118 f., 119 (fig.),

120 (fig.), 221
Herdman, W. A., 187
Heron-Allen, E., 177, 180
Herpetolitha, 70, 70 (fig.)
Herpolitha = Herpetolitha, 70
Herring-bone corallines, 3
Heterocyathus, 38
Heteroderma, 201
Heteropora, 163
Heteropora magna, 164
Heteropsammia, 78, 79 (fig.)
Hickson, S. J., 100, 113, 133, 139,

154
Hincks, T., 173
Holophytic, 21
Holozoic, 17

Homotrema, 180 (fig.), 181
Homotrema rtibrum, 181
Hornera, 162

Hornera lichenoides, 162 (fig.)
Hornera pelliculata, 163, 164
Hornera verrucosa, 163
Huxley, 9

Hydrocorallinae, 145
Hydrozoa, 143
Hydrozoan corals, 143 f.

lace, 249

Imperato, 2, 248

Individual, 9, 57

Isidella, 122

Isidella neapolitaua, 122 (fig.)

Isis, 105 (fig.), 120, 247

Isis hippuris, 121 (fig.), 122, 123

Isophyllia, 59

Isopora, 92

Japanese netsukes, 137

Jaqut, 240

Jelly-fish, 144

Job, 234

Johnson, H., 240

Josephus, 246

Jullien and Calvet, 163, 173

Juncella, 128

Jussieu, B. de, 7

Keratin, 105

King coral, 120
Kirkpatrick, R., 189
Kitahara, 237
von Koch, G., 80

Kollikcr, 8

Labiopora, 135, 136

Lacaze Duthiers, H. de, 16, 28, 43,

79, 80, 107, 141
Lagenipora, 174
Lamarck, 13, 198
Lamentations, 234
Lamouroux, 106, 136
Laufer, B., 233
Lemoine, 203
Lepralia, 167

Lepralia foliacea, 167, 168 (fig.)
Leptogorgia, 128
Lichen millepore, 163
Lindsey, M., 186
Linnaeus, 12, 13, 17, 90, 198
Lister, J. J., 191
Lithodendrnm saccharaceitni album,

145
Lithonina, 191
Lithophyllum, 203, 204 (fig.), 203

(fig.), 221
Lithophyllum brassica florida, 203
Lithophyllum lichenoides, 203
Lithophytes, 13
Lithothamnion, 201 f., 203 (fig.),

221
Lithothamnion dimorplium, 202
Lithothamnion fasciculatum, 202
Lithothamnion glaciate, 202
Lithothamnion lenormandi, 202
Lithothamnion ramulosum, 202
Lithothamnion itngeri, 202
Lobel, 2

Lophogorgia, 127
Lophohelia, 44 (fig.), 192
Lophohelia prolijera, 28 (fig.)
Lophoseridae, 74

M'Intosh, 194, 193
Madracis, 86

Madrepora, 90 f., 92 (fig.), 221
Madrepora foliosa, 97
Madrepora fungites, 69
jMadrepora muricata, 90
Madreporaria, z^ f.
Madrepore, origin of name, 89
Madreporidae, 32, 87 f.
Magicians' stone, 116
Mangan, J., 21

INDEX

255

Manicina, 33 (fig.), 34 (fig.)

Marco Polo, 236

Masson, P., 242

Matthai, 53

Mayer, A. G., 223

Meandrina, 55, 56 (fig.)

Meandrina labvvinthica, 56

Medusa, 232

Medusae of Millepora, 144, 14S

Melitodes, 105 (fig.), 123

Melitodes ochracea, 123

Melitodes variabilis, 124

Melobesia, 201

Merkel, 17S

Media, 188, igr (fig.)

Merlia novmani, 188, 189 (fig.), 190

(fig.)
Merman's shaving brush, 212
MeruUna, 60

Mesenteric filaments, 104
iVIesenteries, 27

of Madreporaria, },z, },}, (fig.)
Metacnemes, 33
Millepora, 145 f., 167, 221

crab gall on, 84

symbiosis in, 21
Alillepora cellulosa, 165
Millepora miniacea, 181
Millepora muricata, 90
Millepora violacea, 152
Milleporina, 145 f.
Milne-Edwards, 6, 7
Minerva, 232
Minns, E. H., 233
Mitra polonica, 70
Mobius, 178
Moliere, 243
Monaxonellidae, 190
Montipora, 96 f.
Moseley, H. N., 145
Mourning fans, 140
Munier Chalmas, 198
Muriceidae, 133
Murray, J., 226
Mushroom coral, 63
Mussa, 57

Nariform process, 155
Nematocysts, 18

of Millepora, 148

of Stylasterina, 150
Neptune's basket, 165
Netsukes, Japanese, 137, 237
Nicolay, 2
Nicolls, 205

Nullipores, 14, 19, 198
Nutrition of corals, 20

Oculina, 29, 46
Oculinidae, 31, 42
O'Donoghue, 164
Ooecium, 161
Opuntia marina, 211
Orbicella, 51
Organ-pipe coral, 112
Orifice, 159
Orpheus, 232
Ovicell, 161
Ovid, 2, 232

Pace, 98, 100
Pachyseris, 75, 75 (fig-)
Pali, '27

Pallas, II, 137, iSi, 198
Palmijuncus anguinus, 140
Paracyathus, 37
Paracyathus carat its, 38 .
Paragorgia, 117
Paragorgia arborea, 117
Parantipathes, 139
Paraphyses, 205
Parkinson, 129, 197, 243
Paulus Aegineta, 237
Pavona, 74
Pelliot, 235
Penicillus, 212
Peninim, 234
Pereira, 244
Periplus, 239, 241
Peritheca, 48
Perseus, 2^2
van Pesch, A. J., 138
Petrostroma schithei, 191
Peyssonnel, 7, 11, 12, 197
Pezalotte, 238
Phallus mariniis, 11
Philhpi, 198
Phylactolaemata, 159
Phyllogorgia, 128
Pillar pores, 178
Pipe corallines, 5
Plant corals, 19
Plesiastraea, 51
Plesio-fungiidae, 72
Plexaura, 132
Plexauridae, 131, 248
Phny, 103, 123, 245, 246, 249
Pliobothrus, 156
Pocillopora, 85
Polychaet worms, 192

2s6

CORALS

Polyp, meaning of the word, 7

{)olyzoan, 158 (fig.)
Polyphyllia, 71
Polvpide, S
Polytrcma, 177
Polytreum cylindriciiin, 182
Polyirema miniaceuui, ijy (fig.)
Polytremacis, 120
Polyzoa, 19, 159
Polvzoan corals, 157 f.
Porella, 170

Porella compressa, 170, 171
Porella concinna, 171
Porifera, 19, 188
Porites, 95, 221

fission in, 35
Porites astraeoides, 96
Poms matronalis ramosiis, 2
Pratt, Edith, 22
Primnoa, 107, 129
Primnoa reseda, 129 f.
Primnoidae, 129
Protocnemes, 32
Protosepta, 36
Pseudaxonia, 135
Pseudopodia, 178
Pterogorgia, 128
Pyrophyllia, 100
Pyrophyllia inflata, loi (fig.)

Quincey, J., 243
De Quincey, T., 231

Ramoth, 234

Ramulina, 187

Ra)mtli)ia herdniaui, 187

Randplatte, 59

Reaumur, 7, 12

Red King coral, 123

Reinach, i, 241

Reseda marina, 129

Retepora, 165

Retepora beaniana, 165

Retepora coii hii, 165

Rhipidogorgia, 125

Rhizopoda, 177

Rhodophyceae, 19, 199

Rotalia, 180

Rotaliform young, 180

Rumphius, 11, 23, 64, 69, 97, 116,

137. 145. 237, 238, 243, 247,

248

Salmacina, 195
Salmasius, 245

Sango, 237

Sav^aglia, 141, 248

Saville-Kent, 67, 94, 95, 96, 97, 99

Sea-cauliflower, 97

Sea-corktree, 117

Sea-mignonette, 129

Sea-rocket, 129

Sea-rope, 129

Sea-rose, 97

Sea-stalk, 129

Sea-weeds, green, 211

red, 199
Sea-whip, 129
Septa, 26

Seriatopora, 82 (fig.), 85
Seriatoporidae, },2, 81 f.
Siderastraea, 71
Siderastraea radians, 71 (fig.)
Siderastraea siderea, 73 (fig.)
Silt, 220 f.

Simpson, W. H., 240
Siphonozooids, 8, 16, 104
Sluiter, 225
Smittia, 171
Sniittia landsborovii, 171
Solenastraea, 53
Solinus, 235, 245, 246
Spadix, 151
Sphenotrochus, 37
Spicules, of Alcyonaria, 105 (fig.)

of Corallium, no (fig.)

of sponges, 188, 192
Spinipora, 156
Sponges, 19, 188
Sporadopora, 155, 156
Sporadotrema, iSo (fig.), 182
Sporadotrema cylindricum, 183
Sporadotrema mesentericum, 183,

184 (fig.)
Stachelkorallen, 136
Stachyodes Verslitysii, 131
Stag's horn coral, 91
Steganopora, 156
Stein, A., 236
Stephanocoenia, 53
Stephens, J., 131
Stereoplasm, 48, 48 (fig.)
Stichopathes spiralis, 140
Stolon, 113
Stolonifera, 135
Stomodaeum, 27, 104
Strachan, 213
Stutchbury, 64

Stylaster, 153, 154 (fig), 156; 222
Stylasterina, 150 f., 221

INDEX

257

Stylophora, 86, 87 (fig.)
Subsidence theory, 224
Sugar coral, red or violet, 152

white, 145
Synapticula, 37, 62

Tabulae, 47, 48 (fig.)

infundibuliforni, 115
Ta vernier, 236
Telesto rubra, 116
Tetraspores, 204
Theca, 26
Thomson, J. A.
Thomson, J. S.,
Tournefort, 177
Townsend, 100,
Tozzetti, 14, ig8
Trade in coral, 231 f.
Trauerfacher, 140
Trembley, 7
Treposomata, 164
Trophodisc, 150
Trophozooid, 68
Tubipora, 105, 107, 112 f., 240
Tubipora musica, 112, 116
Tubipora purpjirea, 116
Tubuliporidae, 161
Turbinaria, 97, 98 (fig.)

130, 139
126

174

Turbinoliidae, 31, 37
Tydemannia, 212
Tylopathes, 140
Tylopora, 92

Ulysses, 245

\'aughan, T. W., 31, 228
Versluys, J., 131
Vesicular corallines, 5
Vine, G. R., 173

Weber van Bosse, 199, 221

Xiphigorgia, 128

Yasz, 249

Yule, H., 236, 238

Yusz, 249

Zoanthidian corals, 141
Zoochlorellae, 21
Zooecium, 159
Zooid, 8

Zoophytes, 10, 143
Zooxanthellae, 20, 148
Zoroaster, 235

THE END

t^tintcd in Great Britain iiy R. & R. Clark, Limii ed, Edinburgh.

MANCHESTER UNIVERSITY BIOLOCilCAL SERIES
No. 3. Price 20s. 'Iff, -cL'://i /ii/z/ieroies illitstratioiis.

THE PRINCIPLES
OF INSECT CONTROL

Bv ROBERT A. WARDLE, M.Sc.

LKCTt'RER IN KCOXOIIIC ZOOLOGV l.\ TIIK UM\EKSITV OF MANCHESTER

PHILIP BUCKLE, M.Sc.

LATE I.ECTlMiEU IN AGKICUI.TU R AL ZOOLOGV IN THE UNUERSITV OF DUR'HAM

PRESS NOTICES

" This book gives in an exceptionally dear and concise way the
approved practices relative to insect control, and of the principles in-
volved. The authors have rendered a distinct service in preparing this
book. It . . . occupies a useful place in the working library of
economic entomologists generally.'' — Journal of the Ainericaii Socieiy
of Agronomy.

"... the first exhaustive work on one of the most important
problems of the day.

" Papers on the theory and practice of control are usually issued in
technical journals, and in various languages. Many are difihcult to
obtain and the student is hampered ; here, aided by an excellent biblio-
graphy, the work accomplished or attempted is explained, and an
invaluable review of economic progress is placed within reach of
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" Messrs. Wardle and Buckle have rendered a distinct service in
providing an excellent resume of the present-day position with regard to
insect control. The volume should appeal to economic entomologists,
since it covers the whole field of a subject which has not been previously
surveyed in so comprehensive a manner." — Nature.

"The authors are to be congratulated in presenting this compilation,
which covers a very wide field, in such an interesting and readable
manner.' — Science Progress.

PRESS NOTICES— contm ned

"This is a valuable and (■()ni|)rehensi\e rt'siiiiit\ world-wide in scope,
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reference work in all fields of economic entomology. It should be in
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libraries of the country." — Joiaiuil of Economic Entomology.

"The book is packed tight with all kinds of useful information. It
will enable the specialist to link up his own branch with others, and to
draw upon them for new ideas. To the beginner it will not only afford
an insight into the methods employed but should offer much inspiration
in indicating how broad is the field, and how much remains to be done.
To the general economic entomologist it will prove a \ery readable
textbook and a handy book of reference."' — Annals of Applied lUology.

■' An orderly comprehensive treatment of the principles of insect
control. A very useful text and reference work." — Proceedings of /lie
Entomological Society of W^asliingfon, D.C.

"A useful compendium of a subject involving ramifications into
many more or less discontinuous branches of natural science.'' — Revii^o
of Applied Entomology.

No. 2. Price i6s. net, Illustrated.

THE QLIANTITATIVE
METHOD IN BIOLOGY

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