Mrs. Humphrey Ward - "Amiel's Journal"

Various - "Ballads of Scottish Tradition and Romance"

J. B. Salmond - "My Man Sandy"

R.V. Russell - "The Tribes and Castes of the Central Provinces of India Volume I (of IV)"

Annual Bibliography of Commonwealth Literature 2007
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




If it were true, he says, that the essential thing in the development of
an animal is this repetition of lower organisations, then certain
deductions could be drawn, which one would expect to find confirmed in
Nature. The first deduction would be that no structures should appear in
the embryo of the higher animals that are not found in the lower
animals. But this is not confirmed by the facts--no adult among the
lower animals, for instance, has a yolk-sac like that of the chick
embryo. Again, if the law of parallelism were true, the mammalian embryo
would have to repeat the organisation of, among other groups, insects
and birds. But the embryo _in utero_ is surrounded by fluid and cannot
possibly breathe free air, so it cannot possibly repeat the structure of
either insects or birds, which are pre-eminently air-organisms.
Generally speaking, indeed, we find in all the higher embryos special
structures which adapt them to the very special conditions of their
development, and these we never find as permanent structures in the
lower animals. The supporters of the theory of parallelism might,
however, admit the existence of such special embryonic organs without
greatly prejudicing their case, for these temporary organs stand to some
extent outside the scope of the theory.

But they would have to face a second and more important deduction from
their views, namely, that the higher animals should repeat at every
stage of their development the whole organisation of some lower animal,
and not merely agree with them in isolated details of structure. The
deduction is, however, not borne out by the facts. The embryo of a
mammal resembles in many points, at different stages of its development,
the adult state of a fish; it has gill-slits and complete aortic arches,
a two-chambered heart, and so on. But at no time does it combine all the
essential characters of a fish; nor has it ever the tail of a fish, nor
the fins, nor the shape. Any recapitulation there may be is a
recapitulation of single organs, there is never a repetition of the
complete organisation of a fish. This is indeed the fundamental
criticism of the theory of parallelism; and if it applies even within
the limits of the vertebrate phylum, so much the more does it apply to
comparisons between embryonic Vertebrates and adult Invertebrates.

There are also some lesser arguments which might be urged against the
theory of parallelism. If the theory were strictly true, no state which
is permanent in a higher animal could be passed through by an animal
lower in the scale. But birds, which are lower in the scale than
mammals, pass through a stage in which they resemble mammals in certain
respects much more than they do when adult, for in an embryonic
condition they agree with mammals in having no feathers, no air sacs, no
pneumatic sacs in the bones, no beak. Their brain also resembles that of
mammals more in an earlier stage than it does later. So, too, myriapods
and hydrachnids have at birth three pairs of feet, and resemble at this
stage adult insects, which form a higher class.

Again, were the analogy between the development of the individual and
the evolution of the _Echelle des etres_ complete, organs and
organ-systems ought to develop in the individual in the order in which
they appear in the scale of beings. But this is not always the case. In
fish the hinder extremity develops only its terminal joint, while in the
embryos of higher animals the basal joint is the first to appear.

Another consequence one would expect to find realised, were the theory
of parallelism correct, is the late appearance in development of parts
which are confined to the higher animals. In the development of a
Vertebrate accordingly one would not expect the vertebrae to appear
before the embryo had passed through many Invertebrate stages. But
experience shows the direct contrary, for in the chick the rudiments of
the vertebral axis appear sooner than any other part.

The theory of parallelism or recapitulation then is not borne out by the
facts, and clearly cannot be the law which we are seeking. But what then
is the true relation between the variety of development and the variety
of adult structure? Before answering this question we must review the
varied forms of adult organisation and consider in what relations they
stand to one another. In particular we must enquire whether they belong
to one type or to many. One point is here cardinal--we must distinguish
between the _type_ of organisation and the _grade_ of differentiation.
By "type" von Baer means the structural plan of the organism. "I call
the _type_ the spatial relationship of the organic elements and organs"
(p. 208). Each type of organisation characterises one of the big groups
of animals; the lesser groups represent "grade" modifications of the
type. "The product of the degree of differentiation and the type gives
the several great groups of animals which are called classes" (p. 208).
_Ausbildung_ (differentiation) takes place in one or other of several
directions, in adaptation, for instance, to life in the water or to life
in the air.

There are, von Baer considers, four main types--(1) the peripheral or
radiate type, (2) the longitudinal type, (3) the massive or molluscan
type, (4) the vertebrate type. The radiate type is shown by discoid
infusoria, by medusae, by starfish and their allies. The longitudinal
type characterises such genera as _Vibrio_, _Filaria_, _Gordius_, and
all the annulate animals. Mollusca, rotifers, polyzoa, and such
infusoria as are not included in types (1) and (2) belong to the massive
type, in which the body and its parts form rounded masses. The
longitudinal type is predominantly "animal," the massive type
predominantly "plastic" (vegetative). The vertebrate type has both the
"animal" and the "plastic" organs highly developed. In the symmetrical
arrangement of the animal parts it resembles the longitudinal type; its
plastic parts with their asymmetrical arrangement and rounded shape
belong to the massive type.

These types of von Baer inevitably recall the "Embranchements" of
Cuvier, with which they more or less coincide. It seems that von Baer
arrived at his types (from the study of adult structure) independently
of Cuvier, though the priority of publication rests with Cuvier.[174]

Now it is clear that the development of the individual, which is
essentially an _Ausbildung_, a differentiation, is directly comparable
with the grade-differentiation of forms within the type. And just as the
type rules all its varied modifications, so does the development of the
individual take place always within the bounds imposed by type. This is
von Baer's chief contribution to the theory of embryonic
relationships--the law that "the type of organisation determines the
manner of development" (p. xxii.). Development is not merely from the
general to the special--there are at least four distinct "general"
types, from which the special is developed. The type is fixed in the
very earliest stages of development--the embryo of a Vertebrate is from
the very beginning a Vertebrate (p. 220), and it shows at no time any
agreement in total organisation with any Invertebrate. The types are
independent of one another; differentiation and development follow a
different course in each of them. Not but what some analogies can be
found between the very earliest stages of embryos of different type.
Thus vertebrate and annulate embryos agree in certain points at the time
of the formation of the primitive streak. And in the earliest stage of
all, the egg-stage, there is probably agreement between all the types.
In eggs with yolk, whether vertebrate or annulate, there is always a
separation into an animal and a plastic layer. It seems, too, as if a
hollow sphere were a constant stage in the development of all animals
(pp. 224, 258). Apart from these analogies, development takes an
entirely independent course in each of the four main types, and no
embryo of one of the higher types repeats in its development the
peculiar organisation of any adult of the lower types.

If we consider now development within the type, which is the only
legitimate thing to do, we arrive at certain laws governing the relation
of embryos to one another. For instance, at a certain stage vertebrate
embryos are uncommonly alike. Von Baer had two in spirit which he was
unable to assign to their class among amniotes; they might have been
lizard, bird, or mammal, he could not say definitely which.[175] Generally
the farther back we go in the development of Vertebrates the more alike
we find the embryos. The type-characters are first to appear, then the
class characters, then the characters distinguishing the lesser
classificatory groups. "From a more general type the special gradually
emerges" (p. 221). The chick is first a Vertebrate, then a
land-vertebrate, then a bird, then a land-bird, then a gallinaceous
bird, and finally _Gallus domesticus_. Development within the type is a
progress from the general to the special, a real evolution. The more
divergent two adults are, the farther back we must go in their
development to find an agreement between their embryos. We can sum up
the case in the following laws:--

"(1) _That the general characters of the big group to which the embryo
belongs appear in development earlier than the special characters._ In
agreement with this is the fact that the vesicular form is the most
general form of all; for what is common in a greater degree to all
animals than the opposition of an internal and an external surface?

"(2) _The less general structural relations are formed after the more
general, and so on until the most special appear._

"(3) _The embryo of any given form, instead of passing through the state
of other definite forms, on the contrary separates itself from them._

"(4) _Fundamentally the embryo of a higher animal form never resembles
the adult of another animal form, but only its embryo_" (p. 224).

These laws relating to development within the limits of type are
destructive of even a limited application of the theory of parallelism,
for not even within the limits of the type is there a real scale which
the higher forms must mount; each embryo develops for itself, and
diverges sooner or later from the embryos of other species, the
divergence coming earlier the greater the difference between the adult
forms. It is only because the lower less-differentiated adult forms
happen to be little divergent from the generalised or embryonic type,
that they show a certain similarity with the embryos of the higher more
differentiated members of the group. Such similarity, however, is due to
no necessary law governing the development of the higher animals; it is,
on the contrary, merely a consequence of the organisation of these lower
animals (p. 224).

Von Baer goes on to show what are the distinguishing embryological
characters of the types and classes, working out a dichotomous schema of
development, which each embryo must follow, branching off early or late
to its terminal point, according to the lower or higher goal it has to
reach.

One important consequence for morphology results from von Baer's laws of
differentiation within the type. If the embryo develops from the general
to the special, then the state in which each organ or organ-system first
appears must represent the general or typical state of that organ within
the group. Embryology will therefore be of great assistance to
comparative anatomy, whose chief aim it is to discover the generalised
type, the common plan of structure, upon which the animals of each big
group are built. And the surest way to determine the true homologies of
parts will be to study their early development. "For since each organ
becomes what it is only through the manner of its development, its true
value can be recognised only from its method of formation. At present,
we form our judgments by an undefined intuition, instead of regarding
each organ merely as an isolated product of its fundamental organ, and
discerning from this standpoint the correspondences and dissimilarities
in the different types" (p. 233). Parts, therefore, which develop from
the same "fundamental organ," and in the last resort from the same
germ-layer, have a certain kinship, which may even reach the degree of
exact homology.

Now since the mode of development in each type is peculiar to that type,
organs of the same name in different types must not necessarily be
accounted homologous, even if they correspond exactly with one another
in their general _functional_ relations to the rest of the organs. Thus
the central nervous system of Arthropods must not be homologised with
the central nervous system of Vertebrates, for it develops in a
different manner. So, too, the brain of Arthropods or of Mollusca is not
strictly comparable with the brain of Vertebrates. Again, the air-tubes
or tracheae of insects are, like the trachea and bronchi of many
Vertebrates, air-breathing organs. But the two organs are not
homologous, for the air-tubes of Vertebrates are developed from the
alimentary tube ("fundamental organ" of the alimentary system, developed
from the vegetative layer), while the air-tubes of insects arise either
by histological differentiation, or by invagination of the skin (p.
236). Organs can be homologous only within the limits of the big groups;
there can be no question of homology between members of different types.

The development of plants, like the development of animals, is
essentially a progress from the general to the special (p. 242).
Botanists have not been troubled by any recapitulation theory, and in
founding their big groups, Acotyledons, Monocotyledons, and
Dicotyledons, upon embryological characters, they were guided by true
principles, which ought indeed to be followed in zoology. If we knew the
development of all kinds of animals sufficiently well, then the best way
to classify them would be according to the characters they show in their
early development, for it is in early development that they show the
characters of the type in their most generalised form. As it is, we have
in our ignorance to establish the big groups by the study of adult
structure, but we find, on putting together all we know of comparative
embryology, that a classification of animals according to the mode of
their development gives, as is only natural, the same four groups as
does the study of adult structure. The four types of development are
thus:--

(1) The double-symmetrical, which is found in Vertebrates. It is called
the double-symmetrical, because in Vertebrates development takes place
from a central axis (notochord) in two directions, upwards and
downwards, in such a way that two tubes are formed, one above and one
below the axis. (2) The second type is the symmetrical, which is shown
by Annulates. A primitive streak is formed on the ventral surface of the
yolk; development proceeds symmetrically on both sides of the streak.
(3) Radiate development is probably typical of the radiate structural
type. (4) In the massive type, the development seems to be a spiral one.

Common to most modes is a separation of the germ into animal and plastic
layers, a separation which seems to be conditioned largely by the
presence of yolk. A classification based upon embryological characters
ought to be applied even to the lesser groups and would here prove
itself of service. Embryology, for instance, fully supports de
Blainville's separation of Batrachia from true reptiles,[176] for reptiles
develop an amnion and Batrachia do not.

We come now to the sixth and last Scholion. Development is a true
evolution of the special from the general, so runs von Baer's most
general law of all. This can be expressed in a slightly different way,
and the words which he chooses in the sixth Scholion to express this
final and most general result are these:--"The developmental history of
the individual is the history of the growing individuality in every
respect" (p. 263). The greatest modern treatise on embryology ends on a
splendid note. One creative thought rules all the forms of life. And
more--"It is this same thought that in cosmic space gathered the
scattered masses into spheres and bound them together in the solar
system, the same that from the weathered dust on the surface of the
metallic planets brought forth the forms of life. And this thought is
nought else but life itself, and the words and syllables in which life
expresses itself are the varied forms of the living" (p. 264).

Von Baer reminds one greatly of Cuvier. There is the same sheer
intellectual power, the same sanity of mind, the same synthetic grip.
Von Baer, like Cuvier, never forgot that he was working with living
things; he was saturated, like Cuvier, with the sense of their
functional adaptedness. In his paper on the external and internal
skeleton[177] he gives a masterly analysis of the functional modifications
of the limbs in Vertebrates, and the whole paper indeed, with its sober
attack on transcendentalism, is a vindication as much of the functional
point of view as of the importance of embryology.

Both Cuvier and von Baer, by the very sanity of their views, found
themselves in partial opposition to the theories current in their time.
Cuvier was the critic of Geoffroy and the transcendentalists, of Lamarck
and the believers in the _Echelle des etres_, evolutionary or ideal. Von
Baer also, though influenced greatly by _Naturphilosophie_, turned
against the exaggerations of the transcendental school, and by his
unanswerable criticism of the theory of parallelism took away the ground
from those who too easily believed in an historical evolution.[178]

We have seen what were von Baer's criticisms of the theory of
parallelism. If we turn to the later writings of Cuvier we find the
essential criticism expressed in similar terms. Speaking of an attempt
which had been made to show that fish were molluscs developed to a
higher degree, he wrote in 1828,[179] "Let us draw the conclusion that
even if these animals can be spoken of as ennobled molluscs, as molluscs
raised to a higher power, or if they are embryos of reptiles, the
beginnings of reptiles, this can be true of them only in an abstract and
metaphysical sense, and that even this abstract statement would be very
far from giving an accurate idea of their organisation." From the fact
that the respiratory and circulatory organs of fish greatly resemble
those of tadpoles the conclusion has been drawn that fish are in a sense
embryos of Amphibia (p. 547). But this manner of viewing things is none
the less vicious, "for this reason ... that it considers only one or two
points and neglects all the others" (p. 548), and is directly contrary
to common sense. There is never a recapitulation of total organisations,
only at the most of single organs.

It will be remembered that Cuvier opposed and demolished the theory of
the _Echelle des etres_, not only by showing that there were in Nature
four entirely different plans of animal structure, but also by
demonstrating that even the animals of each single _Embranchement_ could
not readily be arranged in one series, that a serial arrangement was
really valid only for their separate organs. Von Baer also held that
there are four distinct types of structure; he, too, combated the idea
of gradation within the limits of the type. In so far as species
represent successive stages in the development, the _Ausbildung_, of the
type, so far can the idea of a scale of beings be applied. But the
members of a type follow not one line of evolution but several diverging
lines, in direct adaptation to different environmental conditions, so
that a serial arrangement of them is not as a rule possible. It may be
possible to establish a serial arrangement of single organs from the
simplest to the most complex. But each organ or organ-system will
require a different serial arrangement, for the different systems vary
on different lines and an animal may be highly developed in respect of
one system and little developed in respect of all the others. Man, for
instance, is the highest animal only in respect of his nervous system.
The idea of the scale of beings has therefore only a very limited
application even within the limits of the type. Applied to the whole
animal kingdom it becomes merely absurd.

Another point of resemblance between Cuvier and von Baer was that
Cuvier, though essentially a student of adult structure, did recognise
the importance of embryology; following up some observations of
Dutrochet he studied the foetal membrane of mammals and tried to
establish their homologies.[180] And in his criticism of the vertebral
theory of the skull he advanced as an argument against the
basisphenoid being a vertebral centrum the fact (established
by Kerkring, 1670), that it develops from two centres.[181] Von Baer's
relation to transcendental anatomy was in some ways a close one, though
he was a trenchant critic of the extreme views of the school.[182] He took
from Oken the idea that a simple fundamental plan rules the organisation
of all Vertebrates; "That jaws and limbs are modifications of one
fundamental form is readily apparent, and, after Oken, the fact ought to
be accepted by the majority of those naturalists who do not refuse to
admit the existence of a general type from which the diversity of
structure is developed" (i., p. 192). He accepted the vertebral theory
of the skull in its main lines, and used his embryological knowledge to
support the idea that jaws correspond to limbs--the latter point as part
of the transcendental idea that the hind end of the body repeats the
organisation of the anterior part (i., p. 192). The particular form
which his theory of the relation of jaws to limbs took is shown in the
following passage:--"The maxillary bone has ... the significance of an
extremity and at the same time that of a rib or lower arch of a
vertebra, just as the pelvic bones unite in themselves the signification
of ribs and proximal members of the hinder extremity" (Meckel's
_Archiv_, p. 367, 1826).

He appreciated the morphological idea of the serial repetition of parts,
and gave it accurate formulation. The whole vertebrate body, he
considered, was composed of a longitudinal series of _morphological
elements_, each of which was made up a section from each of the
fundamental organs--a vertebra, a section of the nerve-cord, and so on
(_Entwickelungsgeschichte_, ii., p. 53). Groups of these morphological
elements formed _morphological divisions_, such as the vertebral
segments of the head with their highly developed neural arches, or the
segments of the neck with their undeveloped haemal arches. The
morphological elements are clearly shown only in the animal parts, but
there are indications in the embryo of a segmentation also of the
vegetative parts,--the gill-slits, for instance, and the vascular
arches. The vegetative parts, however, develop on the whole
unsymmetrically (_cf._ Bichat). These elements which von Baer
distinguishes are morphological units, as he himself points out,
contrasting them with organs which are not usually units in a
morphological sense. "We call organ," he writes, "each part that has by
reason of its form or its function a certain distinctiveness, but this
concept is very indefinite, and possesses, from a morphological point of
view, little value. For this reason it seems necessary to introduce into
scientific morphology the concepts of morphological elements and
divisions" (ii., p. 84).

Von Baer exercised a very considerable influence upon the subsequent
trend of morphological theory. By his criticism of the Meckel-Serres
theory, he rid morphology for a time of an idea which was leading it
astray; by his substitution of the law that development is always from
the general to the special, he set morphologists looking for the
archetype in the embryo, not in the adult alone, and made them realise
that homologies could often best be sought in the earliest stages of
development; by formulating the germ-layer theory he supplied
morphologists with a new criterion of homology, based upon the special
relations of the parts (germ-layers) which are first differentiated in
all development. He made the study of development an essential part of
morphology.

[166] _De generatione Animalium_.

[167] _De formato foetu_, ? 1600; _De formatione
foetus_, 1604.

[168] _Exercitationes de generatione animalium_, 1651.

[169] _De formatione pulli in ovo_, 1673; _De ovo
incubato_, 1686.

[170] _De formatione pulli in ovo_, 1757-8; _Sur la
formation du coeur dans le poulet_, 1758.

[171] _Theoria generatioinis_, 1759; _De formatione
intestinorum_, 1768-9.

[172] _Beitraege zur Entwickelung des Huehnchens im Ei._
Wuerzburg, 1818. Also in Latin in shorter form, 1817.

[173] _Untersuchungen ue. die Entwickelungsgeschichte der
Fische_; Leipzig, 1835.

[174] Cuvier, in 1812, _Ann. Mus. d'Hist. Nat._, xix.; von
Baer in 1816, _Nova Acta Acad. Nat. Cur._ See
_Entwickelungsgeschichte der Thiere_, i., p. vii., f.n.

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