Pio Baroja - "Caesar or Nothing"

Elias Owen - "Welsh Folk Lore"

Harry A. Lewis - "Hidden Treasures"

AEsop - "The AEsop for Children"

Editorial
This paper argues that discourses of love in Ghanaian market literature for youth offer a view into complex negotiations of agency and empowerment. Drawing on Deborah Durham's notion of youth as "social `shifters'" and Francis Nyamnjoh's conception of the "interconnectedness" of agency, I take Ghanaian market literature as one specific case of how African literature for youth foregrounds questions of continuity and change as African societies enter into increasingly complex global relations. In this literature for youth, received notions of love, often constructed out of impressions from American pop and hip hop music, carry new notions of agency that compete with existing "domesticated" forms. Authors like Ike Tandoh and Evelyn Tay employ discourses of love to offer youth alternative avenues for empowerment in a context of socio-economic disenfranchizement. In a creative process of "straddling", this writing both reveals and reproduces the contradictions that obtain in youth configurations of agency.

Form and Function

E >> E. S. (Edward Stuart) Russell >> Form and Function



FORM AND FUNCTION

A CONTRIBUTION TO THE
HISTORY OF ANIMAL MORPHOLOGY

By E.S. RUSSELL,
M.A., B.Sc., F.Z.S.

ILLUSTRATED

LONDON

JOHN MURRAY, ALBEMARLE STREET, W.

1916

_All rights reserved_

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| Transcriber's Note: Obvious printer |
| errors have been corrected, all other |
| inconsistencies in spelling and |
| punctuation are as in the original. |
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PREFACE


This book is not intended to be a full or detailed history of animal
morphology: a complete account is given neither of morphological
discoveries nor of morphological theories. My aim has been rather to
call attention to the existence of diverse typical attitudes to the
problems of form, and to trace the interplay of the theories that have
arisen out of them.

The main currents of morphological thought are to my mind three--the
functional or synthetic, the formal or transcendental, and the
materialistic or disintegrative.

The first is associated with the great names of Aristotle, Cuvier, and
von Baer, and leads easily to the more open vitalism of Lamarck and
Samuel Butler. The typical representative of the second attitude is E.
Geoffroy St. Hilaire, and this habit of thought has greatly influenced
the development of evolutionary morphology.

The main battle-ground of these two opposing tendencies is the problem
of the relation of function to form. Is function the mechanical result
of form, or is form merely the manifestation of function or activity?
What is the essence of life--organisation or activity?

The materialistic attitude is not distinctively biological, but is
common to practically all fields of thought. It dates back to the
Greek atomists, and the triumph of mechanical science in the 19th
century has induced many to accept materialism as the only possible
scientific method. In biology it is more akin to the formal than to
the functional attitude.

In the course of this book I have not hidden my own sympathy with the
functional attitude. It appears to me probable that more insight will
be gained into the real nature of life and organisation by
concentrating on the active response of the animal, as manifested both
in behaviour and in morphogenesis, particularly in the post-embryonic
stages, than by giving attention exclusively to the historical aspect
of structure, as is the custom of "pure morphology." I believe we
shall only make progress in this direction if we frankly adopt the
simple everyday conception of living things--which many of us have had
drilled out of us--that they are active, purposeful agents, not mere
complicated aggregations of protein and other substances. Such an
attitude is probably quite as sound philosophically as the opposing
one, but I have not in this place attempted any justification of it. I
have touched very lightly upon the controversy between vitalism and
materialism which has been revived with the early years of the present
century. It hardly lends itself as yet to historical treatment, and I
could hardly hope to maintain with regard to it that objective
attitude which should characterise the historian.

The main result I hope to have achieved with this book is the
demonstration, tentative and incomplete as it is, of the essential
continuity of animal morphology from the days of Aristotle down to our
own time. It is unfortunately true that modern biology, perhaps in
consequence of the great advances it has made in certain directions,
has to a considerable extent lost its historical consciousness, and if
this book helps in any degree to counteract this tendency so far as
animal morphology is concerned, it will have served its purpose.

I owe a debt of gratitude to my friends Dr James F. Gemmill and Prof.
J. Arthur Thomson for much kindly encouragement and helpful criticism.
The credit for the illustrations is due to my wife, Mrs Jehanne A.
Russell. One is from Nature; the others are drawn from the original
figures.

E.S.R.

CHELSEA, 1916.




CONTENTS


CHAP. PAGE

I. THE BEGINNINGS OF COMPARATIVE ANATOMY 1

II. COMPARATIVE ANATOMY BEFORE CUVIER 17

III. CUVIER 31

IV. GOETHE 45

V. ETIENNE GEOFFROY ST HILAIRE 52

VI. THE FOLLOWERS OF ETIENNE GEOFFROY ST HILAIRE 79

VII. THE GERMAN TRANSCENDENTALISTS 89

VIII. TRANSCENDENTAL ANATOMY IN ENGLAND--RICHARD OWEN 102

IX. KARL ERNST VON BAER 113

X. THE EMBRYOLOGICAL CRITERION 133

XI. THE CELL-THEORY 169

XII. THE CLOSE OF THE PRE-EVOLUTIONARY PERIOD 190

XIII. THE RELATION OF LAMARCK AND DARWIN TO MORPHOLOGY 213

XIV. ERNST HAECKEL AND CARL GEGENBAUR 246

XV. EARLY THEORIES ON THE ORIGIN OF VERTEBRATES 268

XVI. THE GERM-LAYERS AND EVOLUTION 288

XVII. THE ORGANISM AS AN HISTORICAL BEING 302

XVIII. THE BEGINNINGS OF CAUSAL MORPHOLOGY 314

XIX. SAMUEL BUTLER AND THE MEMORY THEORIES OF HEREDITY 335

XX. THE CLASSICAL TRADITION IN MODERN MORPHOLOGY 345

INDEX 365




ILLUSTRATIONS


FIG. PAGE

1. HYOID ARCH OF THE CONGER. (ORIGINAL.) 58

2. "VERTEBRA" OF A PLEURONECTID. (GEOFFROY.) 61

3. ABDOMINAL SEGMENT OF THE LOBSTER. (GEOFFROY.) 63

4. IDEAL TYPICAL VERTEBRA. (OWEN.) 102

5. NATURAL TYPICAL VERTEBRA. (OWEN.) 103

6. THE ARCHETYPE OF THE VERTEBRATE SKELETON. (OWEN.) 105

7. IDEAL TRANSVERSE SECTION OF A VERTEBRATE EMBRYO.
(VON BAER.) 119

8. GILL-SLITS OF THE PIG EMBRYO. (RATHKE.) 134

9. MECKEL'S CARTILAGE AND EAR-OSSICLES IN EMBRYO OF
PIG. (REICHERT.) 145

10. CRANIAL VERTEBRAE AND VISCERAL ARCHES IN EMBRYO
OF PIG. (REICHERT.) 148

11. EMBRYONIC CRANIUM OF THE ADDER. (RATHKE.) 152

12. TRANSVERSE SECTION OF CHICK EMBRYO. (REMAK.) 211

13. DEVELOPMENT OF THE ASCIDIAN LARVA (KOWALEVSKY.) 272

14. TRANSVERSE SECTION OF THE WORM _NAIS_. (SEMPER.) 280

15. THE FIVE PRIMARY STAGES OF ONTOGENY. (HAECKEL.) 292


FORM AND FUNCTION




CHAPTER I

THE BEGINNINGS OF COMPARATIVE ANATOMY


The first name of which the history of anatomy keeps record is that of
Alcmaeon, a contemporary of Pythagoras (6th century B.C.). His
interests appear to have been rather physiological than anatomical. He
traced the chief nerves of sense to the brain, which he considered to
be the seat of the soul, and he made some good guesses at the
mechanism of the organs of special sense. He showed that, contrary to
the received opinion, the seminal fluid did not originate in the
spinal cord. Two comparisons are recorded of his, one that puberty is
the equivalent of the flowering time in plants, the other that milk is
the equivalent of white of egg.[1] Both show his bias towards looking
at the functional side of living things. The latter comparison
reappears in Aristotle.

A century later Diogenes of Apollonia gave a description of the venous
system. He too placed the seat of sensation in the brain. He assumed a
vital air in all living things, being in this influenced by Anaximenes
whose primitive matter was infinite air. In following out this thought
he tried to prove that both fishes and oysters have the power of
breathing.[2]

A more strictly morphological note is struck by a curious saying of
Empedocles (4th century B.C.), that "hair and foliage and the thick
plumage of birds are one."[3]

In the collected writings of Hippocrates and his school, the _Corpus
Hippocraticum_, of which no part is later than the end of the 5th
century, there are recorded many anatomical facts. The author of the
treatise "On the Muscles" knew, for instance, that the spinal marrow
is different from ordinary marrow and has membranes continuous with
those of the brain. Embryos of seven days (!) have all the parts of
the body plainly visible. Work on comparative embryology is contained
in the treatise "On the Development of the Child."[4]

The author of the treatise "On the Joints," which Littre calls "the
great surgical monument of antiquity," is to be credited with the
first systematic attempt at comparative anatomy, for he compared the
human skeleton with that of other Vertebrates.

Aristotle (384-322 B.C.)[5] may fairly be said to be the founder of
comparative anatomy, not because he was specially interested in
problems of "pure morphology," but because he described the structure
of many animals and classified them in a scientific way. We shall
discuss here the morphological ideas which occur in his writings upon
animals--in the _Historia Animialium_, the _De Partibus Animalium_,
and the _De Generatione Animalium_.

The _Historia Animalium_ is a most comprehensive work, in some ways
the finest text-book of Zoology ever written. Certainly few modern
text-books take such a broad and sane view of living creatures.
Aristotle never forgets that form and structure are but one of the
many properties of living things; he takes quite as much interest in
their behaviour, their ecology, distribution, comparative physiology.
He takes a special interest in the comparative physiology of
reproduction. The _Historia Animalium_ contains a description of the
form and structure of man and of as many animals as Aristotle was
acquainted with--and he was acquainted with an astonishingly large
number. The later _De Partibus Animalium_ is a treatise on the causes
of the form and structure of animals. Owing to the importance which
Aristotle ascribed to the final cause this work became really a
treatise on the functions of the parts, a discussion of the problems
of the relation of form to function, and the adaptedness of structure.

Aristotle was quite well aware that each of the big groups of animals
was built upon one plan of structure, which showed endless variations
"in excess and defect" in the different members of the group. But he
did not realise that this fact of community of plan constituted a
problem in itself. His interest was turned towards the functional side
of living things, form was for him a secondary result of function.

Yet he was not unaware of facts of form for which he could not quite
find a place in his theory of organic form, facts of form which were
not, at first sight at least, facts of function. Thus he was aware of
certain facts of "correlation," which could not be explained off-hand
as due to correlation of the functions of the parts. He knew, for
instance, that all animals without front teeth in the upper jaw have
cotyledons, while most that have front teeth on both jaws and no horns
have no cotyledons (_De Gen._, ii. 7).

Speaking generally, however, we find in Aristotle no purely
morphological concepts. What then does morphology owe to Aristotle? It
owes to him, _first_, a great mass of facts about the structure of
animals; _second_, the first scientific classification of animals;[6]
_third_, a clear enunciation of the fact of community of plan within
each of the big groups; _fourth_, an attempt to explain certain
instances of the correlation of parts; _fifth_, a pregnant distinction
between homogeneous and heterogeneous parts; _sixth_, a generalisation
on the succession of forms in development; and _seventh_, the first
enunciation of the idea of the _Echelle des etres_.

(1) What surprises the modern reader of the _Historia Animalium_
perhaps more than anything else is the extent and variety of
Aristotle's knowledge of animals. He describes more than 500 kinds.[7]
Not only does he know the ordinary beasts, birds, and fishes with
which everyone is acquainted, but he knows a great deal about
cuttlefish, snails and oysters, about crabs, crawfish (_Palinurus_),
lobsters, shrimps, and hermit crabs, about sea-urchins and starfish,
sea-anemones and sponges, about ascidians (which seem to have puzzled
him not a little!). He has noticed even fish-lice and intestinal
worms, both flat and round. Of the smaller land animals, he knows a
great many insects and their larvae. The extent of his anatomical
knowledge is equally surprising, and much of it is clearly the result
of personal observation. No one can read his account of the internal
anatomy of the chameleon (_Hist. Anim._, ii.), or his description of
the structure of cuttlefish (_Hist. Anim._, iv), or that touch in the
description of the hermit crab (_Hist. Anim._, iv.)--" Two large eyes
... not ... turned on one side like those of crabs, but straight
forward"--without being convinced that Aristotle is speaking of what
he has seen. Naturally he could not make much of the anatomy of small
insects and snails, and, to tell the truth, he does not seem to have
cared greatly about the minutiae of structure. He was too much of a
Greek and an aristocrat to care about laborious detail.

Not only did he lay a foundation for comparative anatomy, but he made
a real start with comparative embryology. Medical men before him had
known many facts about human development; Aristotle seems to have been
the first to study in any detail the development of the chick. He
describes this as it appears to the naked eye, the position of the
embryo on the yolk, the palpitating spot at the third day, the
formation of the body and of the large sightless eyes, the veins on
the yolk, the embryonic membranes, of which he distinguished two.

(2) Aristotle had various systems of classifying animals. They could
be classified, he thought, according to their structure, their manner
of reproduction, their manner of life, their mode of locomotion, their
food, and so on. Thus you might, in addition to structural
classifications, divide animals into gregarious, solitary and social,
or land animals into troglodytes, surface-dwellers, and burrowers
(_Hist. Anim._, i.).

He knew that dichotomous classifications were of little use for
animals (_De Partibus_, i. 3) and he explicitly and in so many words
accepted the principle of all "natural" classification, that
affinities must be judged by comparing not one but the sum total of
characters. As everyone knows, he was the first to distinguish the big
groups of animals, many of which were already distinguished roughly by
the common usages of speech. Among his Sanguinea he did little more
than define with greater exactitude the limits of the groups
established by the popular classification. Among the "exsanguineous"
animals, however, corresponding to our Invertebrates, he established a
much more definite classification than the popular, which is apt to
call them indiscriminately "shellfish," "insects," or "creeping
things." He went beyond the superficialities of popular
classification, too, in clearly separating Cetacea from fishes. He had
some notion of species and genera in our sense. He distinguished many
species of cuttlefish--_Octopus (Polypus)_ of which there were many
kinds, _Eledone (Moschites)_ which he knew to have only one row of
suckers while _Octopus_ has two, _Argonauta, Nautilus, Sepia_, and
apparently _Loligo media_ (= his Teuthis) and _L. vulgaris_(or
_forbesii_) which seems to be his Teuthos. He had a grasp of the
principles which should be followed in judging of the natural
affinities of species. For example, he knew that the cuckoo resembles
a hawk. "But," he says, "the hawk has crooked talons, which the cuckoo
has not, nor does it resemble the hawk in the form of its head, but in
these respects is more like the pigeon than the hawk, which it
resembles in nothing but its colour; the markings, however, upon the
hawk are like lines, while the cuckoo is spotted" (_Hist. Anim._,
Cresswell's trans., p. 147, London, 1862).

The groups he distinguished were--man, viviparous quadrupeds,
oviparous quadrupeds, birds, fishes, Cetacea, Cephalopoda,
Malacostraca (= higher Crustacea), Insecta (= annulose animals),
Testacea (= molluscs, echinoderms, ascidians). A class of Acalephae,
including sea-anemones and sponges, was grouped with the Testacea. The
first five groups were classed together as sanguineous, the others as
exsanguineous, from the presence or absence of red blood.

Besides these classes "there are," he says, "many other creatures in
the sea which it is not possible to arrange in any class from their
scarcity" (Creswell, _loc. cit._, p. 90).

(3) Aristotle's greatest service to morphology is his clear
recognition of the unity of plan holding throughout each of the great
groups.

He recognises this most clearly in the case of man and the viviparous
quadrupeds, with whose structure he was best acquainted. In the
_Historia Animalium_ he takes man as a standard, and describes his
external and internal parts in detail, then considers viviparous
quadrupeds and compares them with man. "Whatever parts a man has
before, a quadruped has beneath; those that are behind in man form the
quadruped's back" (Cresswell, _loc. cit._, p. 26). Apes, monkeys, and
Cynocephali combine the characteristics of man and quadrupeds. He
notices that all viviparous quadrupeds have hair. Oviparous quadrupeds
resemble the viviparous, but they lack some organs, such as ears with
an external pinna, mammae, hair. Oviparous bipeds, or birds, also "have
many parts like the animals described above." He does not, however,
seem to realise that a bird's wings are the equivalent of a mammal's
arms or fore-legs. Fishes are much more divergent; they possess no
neck, nor limbs, nor testicles (meaning a solid ovoid body such as the
testis in mammals), nor mammae. Instead of hair they have scales.

Speaking generally, the Sanguinea differ from man and from one another
in their parts, which may be present or absent, or exhibit differences
in "excess and defect," or in form. Unity of plan extends to all the
principal systems of organs. "All sanguineous animals have either a
bony or a spinous column. The remainder of the bones exist in some
animals; but not in others, for if they have the limbs they have the
bones belonging to them" (Cresswell, _loc. cit._, p. 60). "Viviparous
animals with blood and feet do not differ much in their bones, but
rather by analogy, in hardness, softness, and size" (Cresswell, _loc.
cit._, p. 59). The venous system, too, is built upon the same general
plan throughout the Sanguinea. "In all sanguineous animals, the nature
and origin of the principal veins are the same, but the multitude of
smaller veins is not alike in all, for neither are the parts of the
same nature, nor do all possess the same parts" (Cresswell, _loc.
cit._, p. 56). It will be noticed in the first and last of these three
quotations that Aristotle recognises the fact of correlation between
systems of organs,--between limbs and bones, and between blood-vessels
and the parts to which they go.

Sanguineous animals all possess certain organs--heart, liver, spleen,
kidneys, and so on. Other organs occur in most of the classes--the
oesophagus and the lungs. "The position which these parts occupy is
the same in all animals [sc. Sanguinea]" (Cresswell, _loc. cit._, p.
39).

Unity of plan is observable not only in the Sanguinea, but also within
each of the other large groups. Aristotle recognises that all his
cuttlefish are alike in structure. Among his Malacostraca he compares
point by point the external parts of the carabus (_Palinurus_), and
the astacus (_Homarus_), and he compares also the general internal
anatomy of the various "genera" he distinguishes. As regards Testacea,
he writes, "The nature of their internal structure is similar in all,
especially in the turbinated animals, for they differ in size and in
the relations of excess; the univalves and bivalves do not exhibit
many differences" (Cresswell, _loc. cit._, p. 83). There is an
interesting remark about "the creature called carcinium"
(hermit-crab), that it "resembles both the Malacostraca and the
Testacea, for this in its nature is similar to the animals that are
like carabi, and it is born naked" (Cresswell, _loc. cit._, p. 85). In
the last phrase we may perhaps read the first recognition of the
embryological criterion.

With the recognition of unity of plan within each group necessarily
goes the recognition of what later morphology calls the homology of
parts. The parts of a horse can be compared one by one with the parts
of another viviparous quadruped; in all the animals belonging to the
same class the parts are the same, only they differ in excess or
defect--these remarks are placed in the forefront of the _Historia
Animalium_. Generally speaking, parts which bear the same name are for
Aristotle homologous throughout the class. But he goes further and
notes the essential resemblance underlying the differences of certain
parts. He classes together nails and claws, the spines of the
hedgehog, and hair, as being homologous structures. He says that teeth
are allied to bones, whereas horns are more nearly allied to skin
(_Hist. Anim._, iii.). This is an astonishingly happy guess,
considering that all he had to go upon was the observation that in
black animals the horns are black but the teeth white. One cannot but
admire the way in which Aristotle fixes upon apparently trivial and
commonplace facts, and draws from them far-reaching consequences. He
often goes wrong, it is true, but he always errs in the grand manner.

While Aristotle certainly recognised the existence of homologies, and
even had a feeling for them, he did not clearly distinguish homology
from analogy. He comes pretty near the distinction in the following
passage. After explaining that in animals belonging to the same class
the parts are the same, differing only in excess or defect, he says,
"But some animals agree with each other in their parts neither in form
nor in excess and defect, but have only an analogous likeness, such as
a bone bears to a spine, a nail to a hoof, a hand to a crab's claw,
the scale of a fish to the feather of a bird, for that which is a
feather in the bird is a scale in the fish" (Cresswell, _loc. cit._,
p. 2). One of these comparisons is, however, a homology not an
analogy, and the last phrase throws a little doubt upon the whole
question, for it is not made clear whether it is position or function
that determines what are equivalent organs.

In the _De Partibus Animalium_ there occurs the following
passage:--"Groups that only differ in degree, and in the more or less
of an identical element that they possess, are aggregated under a
single class; groups whose attributes are not identical but analogous
are separated. For instance, bird differs from bird by gradation, or
by excess and defect; some birds have long feathers, others short
ones, but all are feathered. Bird and Fish are more remote and only
agree in having analogous organs; for what in the bird is feather, in
the fish is scale. Such analogies can scarcely, however, serve
universally as indications for the formation of groups, for almost all
animals present analogies in their corresponding parts."[8] It is thus
similarity in form and structure which determines the formation of the
main groups. Within each group the parts differ only in degree, in
largeness or smallness, softness and hardness, smoothness or
roughness, and the like (_loc. cit._, i., 4, 644^b). These passages
show that Aristotle had some conception of homology as distinct from
analogy. He did not, however, develop the idea. What Aristotle sought
in the variety of animal structure, and what he found, were not
homologies, but rather communities of function, parts with the same
attributes. His interest was all in _organs_, in functioning parts,
not in the mere spatial relationship of parts.

This comes out clearly in his treatise _On the Parts of Animals_,
which is subsequent to, and the complement of, his _History of
Animals_. The latter is a description of the variety of animal form,
the former is a treatise on the functions of the parts. He describes
the plan of the _De Partibus Animalium_ as follows:--"We have, then,
first to describe the common functions, common, that is, to the whole
animal kingdom, or to certain large groups, or to members of a
species. In other words, we have to describe the attributes common to
all animals, or to assemblages, like the class of Birds, of closely
allied groups differentiated by gradation, or to groups like Man not
differentiated into subordinate groups. In the first case the common
attributes may be called analogous, in the second generic, in the
third specific" (i, 5, 645^b, trans. Ogle). The alimentary canal is a
good example of a part which is "analogous" throughout the animal
kingdom, for "all animals possess in common those parts by which they
take in food, and into which they receive it" (Cresswell, _loc. cit._,
p. 6).

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