CHAPTER 1
THE MODERN STUDY OF ZOOLOGY
Most of the students AMM taught on his zoology courses were studying for medical rather than zoology degrees and for that reason few of them joined him in practical laboratory research. Given the context, this lecture can be seen as serving at least two important purposes. It is clearly a calling card — a presentation of academic credentials — by a new professor, keen to offer his perspective on the current status of his subject. We might even view it as amounting to an inaugural lecture, although whether some other presentation to the College served that formal role is not recorded.
Its other clear purpose is to introduce students to the subject they are about to study. As medical students, he could reasonably assume that the majority had an appreciation of general science and were capable of absorbing theoretically challenging material. His objective is to provide them with a conceptual framework for the studies they are about to undertake: to set foundations and identify the direction in which zoology was moving.
Regarding AMM's didactic style, one notes the accessible starting point, the use of extended analogy and metaphor to communicate difficult concepts, the occasional use of ironic humour, and the frequent recourse to established authorities for justification. He skilfully draws lessons from history, including from the work of his hero Darwin, and is not afraid to point out where previous interpretations faltered or have been superseded. He establishes his academic authority by demonstrating the extent of his knowledge and his well-informed appreciation of current and past debates.
Many topics discussed in this lecture form the kernels of later, more detailed lectures (indicated in comments). Thus it is an introductory lecture in every sense.
CHAPTER 2
THE MODERN STUDY OF ZOOLOGY
The man of business knows full well — at times too well — the importance of periodical stock-taking; of comparing his actual position with his estimated one, of ascertaining exactly how he stands, of assuring himself that his affairs are in a sound and healthy condition, and that the gain on the year's transactions is a real one. The man who neglects such precautions is apt, sooner or later, to find himself in difficulties: his latest transaction proves a failure, and on attempting to fall back on his former position and start afresh, he finds the ground cut away from beneath him, his reserve fund mysteriously vanished, and his affairs in hopeless confusion.
As in business, so in science, it is well to have periodical stock-takings. Scientific facts accumulate rapidly, and give rise to theories with almost equal rapidity. These theories are often wonderfully enticing, and one is apt to pass from one to another, from theory to theory, without taking care to establish each before passing on to the next, without assuring oneself that the foundation on which one is building is secure. Then comes the crash; the last theory breaks down utterly, and on attempting to retrace our steps to firm ground and start anew, we may find too late that one of the cards, possibly at the very foundation of the pagoda, is either faultily placed or in itself defective, and that this blemish — easily remedied if detected in time — has, neglected, caused the collapse of the whole structure on whose erection so much skill and perseverance have been spent.
Thus men of science find it well occasionally to take stock, to look back for the moment instead of forward, to assure themselves that their operations since the last stock-taking have really resulted in a gain, and to define accurately the nature and extent of that gain.
Science has been aptly compared to a globe, similar to our own earth — a globe with a solid hard crust bounded by an irregular surface. The solid crust represents ascertained facts, facts that have been confirmed and stowed away in their proper places; the irregularity of its surface indicates the unequal accumulation of facts in the various branches of knowledge. The atmosphere by which the whole globe is invested represents the world of speculation, of theories — an atmosphere heavily laden with germs and particles of truth, but germs as yet immature, particles whose position relative to the solid crust is not yet a fixed and determined one.
Our process of stock-taking consists in defining the boundary line between the crust and the atmosphere, between earth and air; such a process becomes periodically necessary because the contour of the surface is constantly changing; particles are continually being added to the crust, while those whose places are already determined are liable by reason of these additions to have their relative positions and importance altered. Thus what was at one time a lofty peak, a startling though established generalisation, may become overshadowed by the formation of a far loftier one by its side, of which the original peak becomes but an insignificant shoulder whose original importance is soon forgotten.
I propose, then, in the present paper to take stock of our zoological knowledge, to attempt to define the actual position and aims of zoological thought, the steps by which this position has been attained, and the methods by which it is hoped to achieve these ends.
Such a process is of special and peculiar interest as applied to zoology, firstly, by reason of the great and rapid accumulation of facts that has occurred of late years; secondly, because of the far-reaching and fiercely contested theories to which these facts have given birth; and, thirdly, because the study of zoology includes the study of man, so that generalisations concerning the rest of the animal kingdom must apply also to man himself. For these reasons, and more especially for the third one, the theories and generalisations of zoology are always subjected to rigid and jealous scrutiny, not only by those who make zoology a special study, but by the world at large.
In order to know clearly with what we are dealing we may, with Professor Huxley, define zoology as "the whole doctrine of animal life," as being in fact, if such marked alliteration may be excused, all about animals. Now, from very remote times indeed there have existed not only names for different animals, but also collective names for groups of animals agreeing with one another in certain respects but differing widely amongst themselves in others; collective names such as fish, under which head a great number of animals are commonly included, some of which, such as the whale, are not fish at all; or birds, including forms as diverse as a starling and a stork, a humming bird and an ostrich. The introduction of such collective names marks the earliest attempts at zoological classification.
Of such classifications we meet with examples in the Old Testament. Thus we read of Solomon that "he spake of trees, from the cedar tree that is in Lebanon even unto the hyssop that springeth out of the wall he spake also of beasts, and of fowl, and of creeping things, and of fishes." The object of the writer in the above passage is manifestly to bring into prominence the extent of Solomon's knowledge, and we are certainly led to believe that Solomon had made a personal study of the several groups of animals mentioned — i.e., that he was a zoologist. The passage quoted bears evidence in itself that the four groups named were intended to include the whole of the animal kingdom; but any doubt on this point is removed by the fact that in other parts of the Old Testament the animal kingdom is distinctly divided into these same four groups. We are therefore justified in speaking of this as a zoological classification.
If we examine this classification more closely we see that the habits of the different animals, and more especially the media in which they live, are made the basis on which the several divisions are founded. Thus beasts include terrestrial animals, animals living on dry land; fowl are those animals that possess the power of flight and so are enabled to live as denizens of the air; fishes are animals adapted for living in water; while creeping things probably included what we now call insects, and any other small forms that could not be referred readily to either of the other groups. Such a system may be spoken of as a classification by distribution. It is one of easy application, and so far a convenient one, but inasmuch as it takes no account whatever of structural and physiological resemblances and differences between the several animals with which it deals it must be regarded as an exceedingly primitive one.
The next classification of any great importance that we meet with is that given by Aristotle, perhaps the greatest and most truly scientific man in the highest sense of the word that the world has ever known. Aristotle, like Solomon, is better known in connection with other branches of knowledge than zoology; still he devoted much attention to the study of animals, and placed zoology on a far more scientific basis than his predecessors had done. It would appear that Aristotle never drew up a formal scheme of classification; the system commonly ascribed to him, which is in reality compiled from his various writings and was never given by him in its modern form, is as follows, the modern equivalents of the several groups being indicated in the right hand column.
A. Animals with red blood and a backbone Vertebrata
1. Provided with four legs
(a) Viviparous Mammalia
(b) Oviparous Reptilia
2. Provided with two legs and two wings Aves
3. Devoid of legs, but provided with fins Pisces, Cetacea
B. Animals without red blood and with no backbone Invertebrata
1. Soft externally Mollusca
2. Soft internally, hard externally Crustacea, Testacea, Insecta
Such a classification is manifestly based on a totally different system to that of Solomon; the several groups are now characterised not by their habits or the media in which they live, but by resemblances and differences in anatomical structure. The branch of zoology that treats of the structure of animals is called Morphology; hence Aristotle's classification may be contrasted with that of Solomon as being not a classification by distribution, but a morphological classification. Inasmuch as the latter springs from a closer and more accurate acquaintance with animals than the former, it is a better and more scientific one and may be taken as marking a distinct and very important advance in the study of zoology.
The next writer on zoology of any great importance is the elder Pliny, who lost his life A.D. 79, at the celebrated eruption of Mount Vesuvius by which Pompeii and Herculaneum were destroyed. Pliny was to a far greater extent than Aristotle a professed zoologist, and left a voluminous work on natural history in thirty-seven books. He divided the animal kingdom into four main groups, which he named as follows:
1. Animalia terrestria;
2. Animalia aquatilia;
3. Volucres;
4. Animalia insecta;
i.e., he classified animals according as they lived on the ground, in the water, or in the air; dividing them into terrestrial, aquatic, and volatile, with a distinct class for those animals, such as insects, which do not belong to any element exclusively.
This is clearly a classification by distribution, and therefore differs totally from that of Aristotle, while it agrees in principle with that of Solomon. This agreement, however, is not only in principle; if the two schemes of classification be compared it will be seen that they are really identical, a point of some interest. Thus, Pliny's Animalia terrestria are the same as the beasts of Solomon; the Animalia aquatilia as the fishes; while Volucres are obviously equivalent to fowl, and Animalia insecta to creeping things. The sole difference between the two systems is in the order in which the several groups are arranged. It would, therefore, appear, that while Aristotle was a long way in advance of any of his predecessors, Pliny, who lived more than 400 years after Aristotle, not only made no advance, but even fell back on the very empirical classification that was in use in the days or Solomon, 1100 years previously, and that had probably been in use for a still longer time.
As Pliny is a writer who owed a considerable part of his reputation to his work on natural history, it may not be inappropriate here to quote the criticism passed on him many centuries after by Cuvier, in order to support my statement that Pliny, instead of placing zoology on a more scientific basis, in reality did it incalculable damage, and threw it back as a science to the condition in which it had been before Aristotle's time. Cuvier's words are as follows: — "In general, he is only a compiler, and, indeed, for the most part, a compiler who has not himself any idea of the subjects on which he collects the testimony of others, and therefore cannot appreciate the truth of their testimonies, nor even always understand what they mean. In short, he is an author devoid of criticism, who, after having spent a great deal of time in making extracts, has ranged them under certain chapters, to which he has added reflections that have no reference to science properly so called, but display alternately either the most superstitious credulity or the declamations of a discontented philosophy, which finds fault continually with mankind, with nature, and with the gods themselves."
Pliny's influence on zoological thought, though most pernicious, was sufficiently great to completely outweigh his illustrious Greek predecessor; and to this must, I think, be ascribed in great part the almost complete gap in zoological literature of any value that extends from the time of the Roman zoologist to about the sixteenth century. It was not, indeed, until nearly the middle of the eighteenth century that a system of zoological classification of any permanent value was proposed. For this we are indebted to the great Swedish naturalist Linnaeus, the founder of modern natural history as he has been well called.
The system of classification proposed by Linnaeus was, like that of Aristotle, a morphological one, based on resemblances and differences of structure in the several animals and groups of animals. He divided the whole animal kingdom into six classes, defined as follows:-
A. Cor biloculare biauritum, sanguine calido rubro.
1. Viviparis. Mammalia.
2. Oviparis. Aves.
B. Cor uniloculare unitarium, sanguine frigido rubro.
1. Pulmone arbitrario. Amphibia.
2. Branchiis externis. Pisces.
C. Cor uniloculare inauritum, sanie frigida alba.
1. Antennatis. Insecta.
2. Tentaculatis. Vermes.
Of morphological classifications there are two principal varieties, classification by definition and classification by type. The Linnaean classification is a typical example of the former of these. In it the whole animal kingdom is divided up into groups of convenient size, each characterised by the presence or absence of some one, two or more easily recognisable features; stress being laid on the differences between the several groups, rather than on the resemblances between the several animals included in each individual group. An illustration will perhaps serve to give a clearer idea of what is meant. Take a piece of paper and make a number of dots on it in a perfectly irregular manner. We want to classify these dots, to arrange them in groups: if we were to classify them by definition, we should divide the paper by means of lines passing between the dots into a number of compartments of convenient size, to which we should give distinctive names; we should then define the position of any one dot by simply saying in which division it was. As our whole paper is divided up, every dot must fall into some one or other of these divisions, so that our classification is at any rate a simple and a convenient one.
