Oliver Fleming - "Ambrotox and Limping Dick"

Gotthold Ephraim Lessing - "Der Freigeist"

Grace S. Richmond - "Under the Country Sky"

J. B. Salmond - "My Man Sandy"

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.

On the Genesis of Species

S >> St. George Mivart >> On the Genesis of Species




Pleurodont lizards are such as have the teeth attached by their sides {148}
to the inner surface of the jaw, in contradistinction to acrodont lizards,
which have the bases of their teeth anchylosed to the summit of the margin
of the jaw. Now pleurodont iguanian lizards abound in the South American
region; but nowhere else, and are not as yet known to inhabit any part of
the present continent of Africa. Yet pleurodont lizards, strange to say,
are found in Madagascar. This is the more remarkable, inasmuch as we have
no evidence yet of the existence in Madagascar of fresh-water fishes common
to Africa and South America.

[Illustration: INNER SIDE OF LOWER JAW OF PLEURODONT LIZARD.
(Showing the teeth attached to the inner surface of its side.)]

Again, that remarkable island Madagascar is the home of very singular and
special insectivorous beasts of the genera Centetes, Ericulus, and
Echinops; while the only other member of the group to which they belong is
Solenodon, which is a resident in the West Indian Islands, Cuba and Hayti.
The connexion, however, between the West Indies and Madagascar must surely
have been at a time when the great lemurine group was absent; for it is
difficult to understand the spread of such a form as Solenodon, and at the
same time the non-extension of the active lemurs, or their utter
extirpation, in such a congenial locality as the West Indian Archipelago.

The close connexion of South America and Australia is demonstrated (on the
Darwinian theory), not only from the marsupial fauna of both, but also from
the frogs and toads which respectively inhabit those regions. A truly
remarkable similarity and parallelism exist, however, between certain of
the same animals inhabiting South Western America and Europe. Thus Dr.{149}
Guenther has described[156] a frog from Chile by the name of cacotus, which
singularly resembles the European bombinator.

[Illustration: SOLENODON.]

Again of the salmons, two genera from South America, New Zealand, and
Australia, are analogous to European salmons.

In addition to this may be mentioned a quotation from Professor Dana, given
by Mr. Darwin,[157] to the effect that "it is certainly a wonderful fact
that New Zealand should have a closer resemblance in its crustacea to Great
Britain, its antipode, than to any other part of the world:" and Mr. Darwin
adds "Sir J. Richardson also speaks of the reappearance on the shores of
New Zealand, Tasmania, &c. of northern forms of fish. Dr. Hooker informs me
that twenty-five species of algae are common to New Zealand and to {150}
Europe, but have not been found in the intermediate tropical seas."

Many more examples of the kind could easily be brought, but these must
suffice. As to the last-mentioned cases Mr. Darwin explains them by the
influence of the glacial epoch, which he would extend actually across the
equator, and thus account, amongst other things, for the appearance in
Chile of frogs having close genetic relations with European forms. But it
is difficult to understand the persistence and preservation of such
exceptional forms with the extirpation of all the others which probably
accompanied them, if so great a migration of northern kinds had been
occasioned by the glacial epoch.

Mr. Darwin candidly says,[158] "I am far from supposing that all
difficulties in regard to the distribution and affinities of the identical
and allied species, which now live so widely separated in the north and
south, and sometimes on the intermediate mountain-ranges, are removed." ...
"We cannot say why certain species and not others have migrated; why
certain species have been modified and have given rise to new forms, whilst
others have remained unaltered." Again he adds, "Various difficulties also
remain to be solved; for instance, the occurrence, as shown by Dr. Hooker,
of the same plants at points so enormously remote as Kerguelen Land, New
Zealand, and Fuegia; but icebergs, as suggested by Lyell, may have been
concerned in their dispersal. The existence, at these and other distant
points of the southern hemisphere, of species which, though distinct,
belong to genera exclusively confined to the south, is a more remarkable
case. Some of these species are so distinct that we cannot suppose that
there has been time since the commencement of the last glacial period for
their migration and subsequent modification to the necessary degree." Mr.
Darwin goes on to account for these facts by the probable existence of a
rich antarctic flora in a warm period anterior to the last glacial {151}
epoch. There are indeed many reasons for thinking that a southern
continent, rich in living forms, once existed. One such reason is the way
in which struthious birds are, or have been, distributed around the
antarctic region: as the ostrich in Africa, the rhea in South America, the
emeu in Australia, the apteryx, dinornis, &c. in New Zealand, the epiornis
in Madagascar. Still the existence of such a land would not alone explain
the various geographical cross relations which have been given above. It
would not, for example, account for the resemblance between the crustacea
or fishes of New Zealand and of England. It would, however, go far to
explain the identity (specific or generic) between fresh water and other
forms now simultaneously existing in Australia and South America, or in
either or both of these, and New Zealand.

Again, mutations of elevation small and gradual (but frequent and
intermitting), through enormous periods of time--waves, as it were, of land
rolling many times in many directions--might be made to explain many
difficulties as to geographical distribution, and any cases that remained
would probably be capable of explanation, as being isolated but allied
animal forms, now separated indeed, but being merely remnants of extensive
groups which, at an earlier period, were spread over the surface of the
earth. Thus none of the facts here given are any serious difficulty to the
doctrine of "evolution," but it is contended in this book that if other
considerations render it improbable that the manifestation of the
successive forms of life has been brought about by minute, indefinite, and
fortuitous variations, then these facts as to geographical distribution
intensify that improbability, and are so far worthy of attention.

All geographical difficulties of the kind would be evaded if we could
concede the probability of the independent origin, in different localities,
of the same organic forms in animals high in the scale of nature. {152}
Similar causes must produce similar results, and new reasons have been
lately adduced for believing, as regards the _lowest organisms_, that the
same forms can arise and manifest themselves independently. The difficulty
as to higher animals is, however, much greater, as (on the theory of
evolution) one acting force must always be the ancestral history in each
case, and this force must always tend to go on acting in the same groove
and direction in the future as it has in the past. So that it is difficult
to conceive that individuals, the ancestral history of which is very
different, can be acted upon by all influences, external and internal, in
such diverse ways and proportions that the results (unequals being added to
unequals) shall be equal and similar. Still, though highly improbable, this
cannot be said to be impossible; and if there _is_ an innate law of any
kind helping to determine specific evolution, this may more or less, or
entirely, neutralize or even reverse the effect of ancestral habit. Thus,
it is quite conceivable that a pleurodont lizard might have arisen in
Madagascar in perfect independence of the similarly-formed American
lacertilia: just as certain teeth of carnivorous and insectivorous
marsupial animals have been seen most closely to resemble those of
carnivorous and insectivorous placental beasts; just as, again, the paddles
of the Cetacea resemble, in the fact of a multiplication in the number of
the phalanges, the many-jointed feet of extinct marine reptiles, and as the
beak of the cuttle-fish or of the tadpole resembles that of birds. We have
already seen (in Chapter III.) that it is impossible, upon any hypothesis,
to escape admitting the independent origins of closely similar forms, It
may be that they are both more frequent and more important than is
generally thought.

That closely similar structures may arise without a genetic relationship
has been lately well urged by Mr. Ray Lankester.[159] He has brought {153}
this notion forward even as regards the bones of the skull in osseous
fishes and in mammals. He has done so on the ground that the probable
common ancestor of mammals and of osseous fishes was a vertebrate animal of
so low a type that it could not be supposed to have possessed a skull
differentiated into distinct bony elements--even if it was bony at all. If
this was so, then the cranial bones must have had an independent origin in
each class, and in this case we have the most strikingly harmonious and
parallel results from independent actions. For the bones of the skull in an
osseous fish are so closely conformed to those of a mammal, that "both
types of skull exhibit many bones in common," though "in each type some of
these bones acquire special arrangements and very different
magnitudes."[160] And no investigator of homologies doubts that a
considerable number of the bones which form the skull of any osseous fish
are distinctly homologous with the cranial bones of man. The occipital, the
parietal, and frontal, the bones which surround the internal ear, the
vomer, the premaxilla, and the quadrate bones, may be given as examples.
Now, if such close relations of homology can be brought about independently
of any but the most remote genetic affinity, it would be rash to affirm
dogmatically that there is any impossibility in the independent origin of
such forms as centetes and solenodon, or of genetically distinct
batrachians, as similar to each other as are some of the frogs of South
America and of Europe. At the same time such phenomena must at present be
considered as very improbable, from the action of ancestral habit, as
before stated.

We have seen, then, that the geographical distribution of animals presents
difficulties, though not insuperable ones, for the Darwinian hypothesis.
If, however, other reasons against it appear of any weight--if, especially,
there is reason to believe that geological time has not been {154}
sufficient for it, then it will be well to bear in mind the facts here
enumerated. These facts, however, are not opposed to the doctrine of
evolution; and if it could be established that closely similar forms had
really arisen in complete independence one of the other, they would rather
tend to strengthen and to support that theory. [Page 155]

* * * * *


CHAPTER VIII.

HOMOLOGIES.

Animals made-up of parts mutually related in various ways.--What
homology is.--Its various kinds.--Serial homology.--Lateral
homology.--Vertical homology.--Mr. Herbert Spencer's explanations.--An
internal power necessary, as shown by facts of comparative anatomy.--Of
teratology.--M. St. Hilaire.--Professor Burt
Wilder.--Foot-wings.--Facts of pathology.--Mr. James Paget.--Dr.
William Budd.--The existence of such an internal power of individual
development diminishes the improbability of an analogous law of
specific origination.

That concrete whole which is spoken of as "an individual" (such, _e.g._, as
a bird or a lobster) is formed of a more or less complex aggregation of
parts which are actually (from whatever cause or causes) grouped, together
in a harmonious interdependency, and which have a multitude of complex
relations amongst themselves.

The mind detects a certain number of these relations as it contemplates the
various component parts of an individual in one or other direction--as it
follows up different lines of thought. These perceived relations, though
subjective, _as relations_, have nevertheless an objective foundation as
real parts, or conditions of parts, of real wholes; they are, therefore,
true relations, such, _e.g._, as those between the right and left hand,
between the hand and the foot, &c.

The component parts of each concrete whole have also a relation of
resemblance to the parts of other concrete wholes, whether of the same{156}
or of different kinds, as the resemblance between the hands of two men, or
that between the hand of a man and the fore-paw of a cat.

Now, it is here contended that the relationships borne one to another by
various component parts, imply the existence of some innate, internal
condition, conveniently spoken of as a power or tendency, which is quite as
mysterious as is any innate condition, power, or tendency, resulting in the
orderly evolution of successive specific manifestations. These
relationships, as also this developmental power, will doubtless, in a
certain sense, be somewhat further explained as science advances. But the
result will be merely a shifting of the inexplicability a point backwards,
by the intercalation of another step between the action of the internal
condition or power and its external result. In the meantime, even if by
"Natural Selection" we could eliminate the puzzles of the "origin of
species," yet other phenomena, not less remarkable (namely, those noticed
in this chapter), would still remain unexplained and as yet inexplicable.
It is not improbable that, could we arrive at the causes conditioning all
the complex inter-relations between the several parts of one animal, we
should at the same time obtain the key to unlock the secrets of specific
origination.

It is desirable, then, to see what facts there are in animal organization
which point to innate conditions (powers and tendencies), as yet
unexplained, and upon which the theory of "Natural Selection" is unable to
throw any explanatory light.

The facts to be considered are the phenomena of "homology," and especially
of serial, bilateral, and vertical homology.

The word "homology" indicates such a relation between two parts that they
may be said in some sense to be "the same," or at least "of similar
nature." This similarity, however, does not relate to the _use_ to which
parts are put, but only to their relative position with regard to other
parts, or to their mode of origin. There are many kinds of {157}
homology,[161] but it is only necessary to consider the three kinds above
enumerated.

[Illustration: WINGBONES OF PTERODACTYLE, BAT, AND BIRD.]

The term "homologous" may be applied to parts in two individual animals of
different kinds, or to different parts of the same individual. Thus "the
right and left hands," or "joints of the backbone," or "the teeth of the
two jaws," are homologous parts of the same individual. But the arm of a
man, the fore-leg of the horse, the paddle of the whale, and the wing of
the bat and the bird are all also homologous parts, yet of another kind,
_i.e._ they are the same parts existing in animals of different species.

On the other hand, the wing of the humming-bird and the wing of the
humming-bird moth are not homologous at all, or in any sense; for the
resemblance between them consists solely in the use to which they are put,
and is therefore only a relation of _analogy_. There is no relation of
_homology_ between them, because they have no common resemblance as to
their relations to surrounding parts, or as to their mode of origin.
Similarly, there is no homology between the wing of the bat and that {158}
of the flying-dragon, for the latter is formed of certain ribs, and not of
limb bones.

[Illustration: SKELETON OF THE FLYING DRAGON.
(Showing the elongated ribs which support the flitting organ.)]

Homology may be further distinguished into (1) a relationship which, on
evolutionary principles, would be due to descent from a common ancestor, as
the homological relation between the arm-bone of the horse and that of the
ox, or between the singular ankle bones of the two lemurine genera,
cheirogaleus and galago, and which relation has been termed by Mr. Ray
Lankester "homogeny;"[162] and (2) a relationship induced, not
derived--such as exists between parts closely similar in relative position,
but with no genetic affinity, or only a remote one, as the homological
relation between the chambers of the heart of a bat and those of a {159}
bird, or the similar teeth of the thylacine and the dog before spoken of.
For this relationship Mr. Bay Lankester has proposed the term "homoplasy."

[Illustration: TARSAL BONES OF DIFFERENT LEMUROIDS.
(Right tarsus of Galago; left tarsus of Cheirogaleus.)]

[Illustration: A CENTIPEDE.]

"Serial homology" is a relation of resemblance existing between two or more
parts placed in series one behind the other in the same individual.
Examples of such homologues are the ribs, or joints of the backbone of{160}
a horse, or the limbs of a centipede. The latter animal is a striking
example of serial homology. The body (except at its two ends) consists of a
longitudinal series of similar segments. Each segment supports a pair of
limbs, and the appendages of all the segments (except as before) are
completely alike.

[Illustration: SQUILLA.]

A less complete case of serial homology is presented by Crustacea (animals
of the crab class), notably by the squilla and by the common lobster. In
the latter animal we have a six-jointed abdomen (the so-called tail), {161}
in front of which is a large solid mass (the cephalo-thorax), terminated
anteriorly by a jointed process (the rostrum). On the under surface of the
body we find a quantity of moveable appendages. Such are, _e.g._, feelers
(Fig. 9), jaws (Figs. 6, 7, and 8), foot-jaws (Fig. 5), claws and legs
(Figs. 3 and 4), beneath the cephalo-thorax; and flat processes (Fig. 2),
called "swimmerets," beneath the so-called tail or abdomen.

[Illustration: PART OF THE SKELETON OF THE LOBSTER.]

Now, these various appendages are distinct and different enough as we {162}
see them in the adult, but they all appear in the embryo as buds of similar
form and size, and the thoracic limbs at first consist each of two members,
as the swimmerets always do.

This shows what great differences may exist in size, in form, and in
function, between parts which are developmentally the same, for all these
appendages are modifications of one common kind of structure, which becomes
differently modified in different situations; in other words, they are
serial homologues.

The segments of the body, as they follow one behind the other, are also
serially alike, as is plainly seen in the abdomen or tail. In the
cephalo-thorax of the lobster, however, this is disguised. It is therefore
very interesting to find that in the other crustacean before mentioned, the
squilla, the segmentation of the body is more completely preserved, and
even the first three segments, which go to compose the head, remain
permanently distinct.

[Illustration: SPINE OF GALAGO ALLENII.]

Such an obvious and unmistakeable serial repetition of parts does not
obtain in the highest, or backboned animals, the Vertebrata. Thus in man
and other mammals, nothing of the kind is _externally_ visible, and we have
to penetrate to his skeleton to find such a series of homologous parts.

There, indeed, we discover a number of pairs of bones, each pair so
obviously resembling the others, that they all receive a common name--the
ribs. There also (_i.e._ in the skeleton) we find a still more remarkable
series of similar parts, the joints of the spine or backbone (vertebrae),
which are admitted by all to possess a certain community of structure.{163}

It is in their limbs, however, that the Vertebrata present the most obvious
and striking serial homology--almost the only serial homology noticeable
externally.

The facts of serial homology seem hardly to have excited the amount of
interest they certainly merit.

Very many writers, indeed, have occupied themselves with investigations and
speculations as to what portions of the leg and foot answer to what parts
of the arm and hand, a question which has only recently received a more or
less satisfactory solution through the successive concordant efforts of
Professor Humphry,[163] Professor Huxley,[164] the Author of this
work,[165] and Professor Flower.[166] Very few writers, however, have
devoted much time or thought to the question of serial homology in general.
Mr. Herbert Spencer, indeed, in his very interesting "First Principles of
Biology," has given forth ideas on this subject, which are well worthy
careful perusal and consideration, and some of which apply also to the
other kinds of homology mentioned above. He would explain the serial
homologies of such creatures as the lobster and centipede thus: Animals of
a very low grade propagate themselves by spontaneous fission. If certain
creatures found benefit from this process of division remaining incomplete,
such creatures (on the theory of "Natural Selection") would transmit their
selected tendency to such incomplete division to their posterity. In this
way, it is conceivable, that animals might arise in the form of long chains
of similar segments, each of which chains would consist of a number of
imperfectly separated individuals, and be equivalent to a series of
separate individuals belonging to kinds in which the fission was complete.
In other words, Mr. Spencer would explain it as the coalescence of {164}
organisms of a lower degree of aggregation in one longitudinal series,
through survival of the fittest aggregations. This may be so. It is
certainly an ingenious speculation, but facts have not yet been brought
forward which demonstrate it. Had they been so, this kind of serial
homology might be termed "homogenetic."

The other kind of serial repetitions, namely, those of the vertebral
column, are explained by Mr. Spencer as the results of alternate strains
and compressions acting on a primitively homogeneous cylinder. The serial
homology of the fore and hind limbs is explained by the same writer as the
result of a similarity in the influences and conditions to which they are
exposed. Serial homologues so formed might be called, as Mr. Ray Lankester
has proposed, "homoplastic." But there are, it is here contended, abundant
reasons for thinking that the predominant agent in the production of the
homologies of the limbs is an _internal_ force or tendency. And if such a
power can be shown to be necessary in this instance, it may also be
legitimately used to explain such serial homologies as those of the
centipede's segments and of the joints of the backbone. At the same time it
is not, of course, pretended that external conditions do not contribute
their own effects in addition. The presence of this internal power will be
rendered more probable if valid arguments can be brought forward against
the explanations which Mr. Herbert Spencer has offered.

_Lateral homology_ (or bilateral symmetry) is the resemblance between the
right and left sides of an animal, or of part of an animal; as, _e.g._,
between our right hand and our left. It exists more or less at one or other
time of life in all animals, except some very lowly organized creatures. In
the highest animals this symmetry is laid down at the very dawn of life,
the first trace of the future creature being a longitudinal streak--the
embryonic "primitive groove." This kind of homology is explained by Mr.
Spencer as the result of the similar way in which conditions affect {165}
the right and left sides respectively.

[Illustration: VERTEBRAE OF AXOLOTL.]

_Vertical homology_ (or vertical symmetry) is the resemblance existing
between parts which are placed one above the other beneath. It is much less
general and marked than serial, or lateral homology. Nevertheless, it is
plainly to be seen in the tail region of most fishes, and in the
far-extending dorsal (back) and ventral (belly) fins of such kinds as the
sole and the flounder.

It is also strikingly shown in the bones of the tail of certain efts, as in
_Chioglossa_, where the complexity of the upper (neural) arch is closely
repeated by the inferior one. Again, in _Spelerpes rubra_, where almost
vertically ascending articular processes above are repeated by almost
vertically descending articular processes below. Also in the axolotl, where
there are douple pits, placed side by side, not only superiorly but at the
same time inferiorly.[167]

This kind of homology is also explained by Mr. Spencer as the result of the
similarity of conditions affecting the two parts. Thus he explains the very
general absence of symmetry between the dorsal and ventral surfaces of
animals by the different conditions to which these two surfaces are
respectively exposed, and in the same way he explains the asymmetry of the
flat-fishes (_Pleuronectidae_), of snails, &c.

Now, first, as regards Mr. Spencer's explanation of animal forms by means
of the influence of external conditions, the following observations may be
made. Abundant instances are brought forward by him of admirable adaptation
of structure to circumstances, but as to the immense majority of these it
is very difficult, if not impossible, to see _how_ external conditions{166}
can have produced, or even tended to have produced them. For example, we
may take the migration of one eye of the sole to the other side of its
head. What is there here either in the darkness, or the friction, or in any
other conceivable external cause, to have produced the first beginning of
such an unprecedented displacement of the eye? Mr. Spencer has beautifully
illustrated that correlation which all must admit to exist between the
forms of organisms and their surrounding external conditions, but by no
means proved that the latter are _the cause_ of the former.

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