IV. Professor Haeckel proposes a number of modifications in Taxonomy, all of which are well worthy of consideration. Thus he establishes a third primary division of the living world, distinct from both animals and plants, under the name of the _Protista_, to include the _Myxomycetes_, the _Diatomaceae_, and the _Labyrinthulae_, which are commonly regarded as plants, with the _Noctilucae_, the _Flagellata_, the _Rhizopoda_, the _Protoplasta_, and the _Monera_, which are most generally included within the animal world. A like attempt has been made, by other writers, to escape the inconvenience of calling these dubious organisms by the name of plant or animal; but I confess, it appears to me, that the inconvenience which is eluded in one direction, by this step, is met in two others. Professor Haeckel himself doubts whether the _Fungi_ ought not to be removed into his _Protista_. If they are not, indeed, the _Myxomycetes_ render the drawing of every line of demarcation between _Protista_ and Plants impossible. But if they are, who is to define the _Fungi_ from the _Algae_? Yet the sea-weeds are surely, in every respect, plants.
On the other hand, Professor Haeckel puts the sponges among the _Coelenterata_ (or polypes and corals), with the double inconvenience, as it appears to me, of separating the sponges from their immediate kindred, the _Protoplasta_, and destroying the definition of the _Coelenterata_. So again, the _Infusoria_ possess all the characters of animality, but it can hardly be said that they are as clearly allied to the worms as they are to the _Noctilucae_.
On the whole, it appears to me to be most convenient to adhere to the old plan of calling such of these low forms as are more animal in habit, _Protozoa_, and such as are more vegetal, _Protophyta_.
Another considerable innovation is the proposition to divide the cla.s.s Pisces into the four groups of _Leptocardia, Cyclostomata, Pisces_, and _Dipneusta_. As regards the establishment of a separate cla.s.s for the Lancelet _(Amphioxus)_, I think there can be little doubt of the propriety of so doing, inasmuch as it is far more different from all other fishes than they are from one another. And there is much to be said in favour of the same promotion of the _Cyclostomata_, or Lampreys and Hags. But considering the close relation of the Mudfish with the _Ganoidei_, and the wide differences between the _Elasmobranchii_ and the _Teleostei_, I greatly doubt the propriety of separating the _Dipneusta_, as a cla.s.s, from the other _Pisces_.
Professor Haeckel proposes to break up the vertebrate sub-kingdom, first, into the two provinces of _Leptocardia_ and _Pachycardia; Amphioxus_ being in the former, and all other vertebrates in the latter division. The _Pachycardia_ are then divided into _Monorhina_, which contains the Cyclostome fishes, distinguished by their single nasal aperture; and _Amphirhina_, comprising the other _Vertebrata_, which have two nasal apertures. These are further subdivided into _Anamnia (Pisces, Dipneusta, Amphibia)_ and _Amniota (Reptilia, Aves, Mammalia)_. This cla.s.sification undoubtedly expresses many of the most important facts in vertebrate structure in a clear and compendious way; whether it is the best that can he adopted remains to be seen.
With much reason the Lemurs are removed altogether from the _Primates_, under the name of _Prosimiae_. But I am surprised to find the _Sirenia_ left in one group with the _Cetacea_, and the _Plesiosauria_ with the _Ichthyosauria_; the ordinal distinctness of these having, to my mind, been long since fully established.
V. In Professor Haeckel"s speculations on Phylogeny, or the genealogy of animal forms, there is much that is profoundly interesting, and his suggestions are always supported by sound knowledge and great ingenuity. Whether one agrees or disagrees with him, one feels that he has forced the mind into lines of thought in which it is more profitable to go wrong than to stand still.
To put his views into a few words, he conceives that all forms of life originally commenced as _Monera_, or simple particles of protoplasm; and that these _Monera_ originated from not-living matter. Some of the _Monera_ acquired tendencies towards the Protistic, others towards the Vegetal, and others towards the Animal modes of life. The last became animal _Monera_. Some of the animal _Monera_ acquired a nucleus, and became amoeba-like creatures; and, out of certain of these, ciliated infusorium-like animals were developed. These became modified into two stirpes: A, that of the worms; and B, that of the sponges. The latter by progressive modification gave rise to all the _Coelenterata_; the former to all other animals. But A soon broke up into two princ.i.p.al stirpes, of which one, _a_, became the root of the _Annelida, Echinodermata_, and _Arthropoda_, while the other, _b_, gave rise to the _Polyzoa_ and _Ascidioida_, and produced the two remaining stirpes of the _Vertebrata_ and the _Mollusca_.
Perhaps the most startling proposition of all those which Professor Haeckel puts before us is that which he bases upon Kowalewsky"s researches into the development of _Amphioxus_ and of the _Ascidioida_, that the origin of the _Vertebrata_ is to be sought in an Ascidioid form. Goodsir long ago insisted upon the resemblance between _Amphioxus_ and the Ascidians; but the notion of a genetic connection between the two, and especially the identification of the notochord of the _Vertebrate_ with the axis of the caudal appendage of the larva of the Ascidian, is a novelty which, at first, takes one"s breath away. I must confess, however, that the more I have pondered over it, the more grounds appear in its favour, though I am not convinced that there is any real parallelism between the mode of development of the ganglion of the _Ascidian_ and that of the _Vertebrate_ cerebro-spinal axis.
The hardly less startling hypothesis that the _Echinoderms_ are coalesced worms, on the other hand, appears to be open to serious objection. As a matter of anatomy, it does not seem to me to correspond with fact; for there is no worm with a calcareous skeleton, nor any which has a band-like ventral nerve, superficial to which lies an ambulacral vessel. And, as a question of development, the formation of the radiate _Echinoderm_ within its vermiform larva seems to me to be a.n.a.logous to the formation of a radiate Medusa upon a Hydrozoic stock. But a Medusa is surely not the result of the coalescence of as many organisms as it presents morphological segments.
Professor Haeckel adduces the fossil _Crossopodia_ and _Phyllodocites_ as examples of the Annelidan forms, by the coalescence of which the Echinoderms may have been produced; but, even supposing the resemblance of these worms to detached starfish arms to be perfect, it is possible that they may be the extreme term, and not the commencement, of Echinoderm development. A pentacrinoid Echinoderm, with a complete jointed stalk, is developed within the larva of _Antedon_. Is it not possible that the larva of _Crossopodia_ may have developed a vermiform Echinoderm?
With respect to the Phylogeny of the _Arthropoda_, I find myself disposed to take a somewhat different view from that of Professor Haeckel. He a.s.sumes that the primary stock of the whole group was a crustacean, having that _Nauplius_ form in which Fritz Muller has shown that so many _Crustacea_ commence their lives. All the _Entomostraca_ arose by the modification of some one or other of these Naupliform "_Archicarida_." Other _Archicarida_ underwent a further metamorphosis into a _Zoaea_-form. From some of these "_Zoeopoda_"
arose all the remaining Malacostracous _Crustacea_; while, from others, was developed some form a.n.a.logous to the existing _Galeodes_, out of which proceeded, by gradual differentiation, all the _Myriapoda, Arachnida,_ and _Insecta_.
I should, be disposed to interpret the facts of the embryological history and of the anatomy of the _Arthropoda_ in a different manner.
The _Copepoda_, the _Ostracoda_, and the _Branchiopoda_ are the _Crustacea_ which have departed least from the embryonic or _Nauplius_-forms; and, of these, I imagine that the _Copepoda_ represent the hypothetical _Archicarida_ most closely. _Apus_ and _Sapphirina_ indicate the relations of these Archaeocarids with the _Trilobita_, and the _Eurypterida_ connect the _Trilobita_ and the _Copepoda_ with the _Xiphosura_. But the _Xiphosura_ have such close morphological relations with the _Arachnida_, and especially with the oldest known Arachnidan, _Scorpio_, that I cannot doubt the existence of a genetic connection between the two groups. On the other hand, the _Branchiopoda_ do, even at the present day, almost pa.s.s into the true _Podophthalmia_, by _Nebalia_. By the _Trilobita_, again, the _Archicarida_ are connected with such _Edriophthalmia_ as _Serolis_.
The _Stomapoda_ are extremely modified _Edriophthalmia_ of the amphipod type. On the other side, the _Isopoda_ lead to the _Myriapoda_, and the latter to the _Insecta_. Thus the Arthropod phylum, which suggests itself to me, is that the branches of the _Podophthalmia_, of the _Insecta_ (with the _Myriapoda_), and of the _Arachnida_, spring separately and distinctly from the Archaeocarid root--and that the _Zoaea_-forms occur only at the origin of the Podophthalmous branch.
The phylum of the _Vertebrata_ is the most interesting of all, and is admirably discussed by Professor Haeckel. I can note only a few points which seem to me to be open to discussion. The _Monorhina_, having been developed out of the _Leptocardia_, gave rise, according to Professor Haeckel, to a shark-like form, which was the common stock of all the _Amphirhina_. From this "Protamphirhine" were developed, in divergent lines, the true Sharks, Rays, and _Chimaerae_; the Ganoids, and the _Dipneusta_. The _Teleostei_ are modified _Ganoidei_. The _Dipneusta_ gave rise to the _Amphibia_, which are the root of all other _Vertebrata_, inasmuch as out of them were developed the first _Vertebrata_ provided with an amnion, or the _Protamniota_. The _Protamniota_ split up into two stems, one that of the _Mammalia_, the other common to _Reptilia_ and _Aves_.
The only modification which it occurs to me to suggest in this general view of the Phylogeny of the _Vertebrata_ is, that the "Protamphirhine" was possibly more ganoid than shark-like. So far as our present information goes the Ganoids are as old as the Sharks; and it is very interesting to observe that the remains of the oldest Ganoids, _Cephalaspis_ and _Pteraspis_, have as yet displayed no trace of jaws. It is just possible that they may connect the _Monorhina_, with the Sturgeons among the _Amphirhina_. On the other hand, the Crossopterygian Ganoids exhibit the closest connection with _Lepidosiren_, and thereby with the _Amphibia_. It should not be forgotten that the development of the Lampreys exhibits curious points of resemblance with that of the _Amphibia_, which are absent in the Sharks and Rays. Of the development of the _Ganoidei_ we have unfortunately no knowledge, but their brains and their reproductive organs are more amphibian than are those of the Sharks.
On the whole, I am disposed to think that the direct stem of ascent from the _Monorhina_ to the _Amphibia_ is formed by the Ganoids and the Mudfishes; while the Osseous fishes and the Sharks are branches in different directions from this stem.
What the _Protamniota_ were like, I do not suppose any one is in a position to say, but I cannot think that the thoroughly Lacertian _Protorosaurus_ had anything to do with them. The reptiles which are most amphibian in their characters, and therefore, probably, most nearly approach the _Protamniota_, are the _Ichthyosauria_ and the _Chelonia_.
That the _Didelphia_ were developed out of some ornithodelphous form, as Professor Haeckel supposes, seems to be unquestionable; but the existing Opossums and Kangaroos are certainly extremely modified and remote from their ancestors the "_Prodidelphia_," of which we have not, at present the slightest knowledge. The mode of origin of the _Monodelphia_ from these is a very difficult problem, for the most part left open by Professor Haeckel. He considers the _Prosimiae_, or Lemurs, to be the common stock of the _Deciduata_, and the _Cetacea_ (with which he includes the _Sirenia_) to be modified _Ungulata_. As regards the latter question, I have little doubt that the _Sirenia_ connect the _Ungulata_ with the _Proboscidea_; and none, that the _Cetacea_ are extremely modified _Carnivora_. The pa.s.sage between the Seals and the _Cetacea_ by _Zeuglodon_ is complete. I also think that there is much to be said for the opinion, that the _Insectivora_ represent the common stock of the _Primates_ (which pa.s.sed into them by the _Prosimiae_), the _Cheiroptera_, the _Rodentia_, and the _Carnivora_. And I am greatly disposed to look for the common root of all the _Ungulata_, as well, in some ancient non-deciduate Mammals which were more like _Insectivora_ than anything else. On the other hand, the _Edentata_ appear to form a series by themselves.
The latter part of this notice of the _Naturliche Schopfungs-Geschichte_, brings so strongly into prominence the points of difference between its able author and myself, that I do not like to conclude without reminding the reader of my entire concurrence with the general tenor and spirit of the work, and of my high estimate of its value.
XII.
BISHOP BERKELEY ON THE METAPHYSICS OF SENSATION.[1]
Professor Fraser has earned the thanks of all students of philosophy for the conscientious labour which he has bestowed upon his new edition of the works of Berkeley; in which, for the first time, we find collected together every thought which can be traced to the subtle and penetrating mind of the famous Bishop of Cloyne; while the "Life and Letters" will rejoice those who care less for the idealist and the prophet of tar-water, than for the man who stands out as one of the n.o.blest and purest figures of his time: that Berkeley from whom the jealousy of Pope did not withhold a single one of all "the virtues under heaven;" nor the cynicism of Swift, the dignity of "one of the first men of the kingdom for learning and virtue;" the man whom the pious Atterbury could compare to nothing less than an angel; and whose personal influence and eloquence filled the Scriblerus Club and the House of Commons with enthusiasm for the evangelization of the North American Indians; and even led Sir Robert Walpole to a.s.sent to the appropriation of public money to a scheme which was neither business nor bribery.[2]
[Footnote 1: "The Works of George Berkeley, D.D., formerly Bishop of Cloyne, including many of his Works. .h.i.therto unpublished, with Preface, Annotations, his Life and Letters, and an Account of his Philosophy." By A.C. Fraser. Four vols. Oxford: Clarendon Press.
1871.]
[Footnote 2: In justice to Sir Robert, however, it is proper to remark that he declared afterwards, that he gave his a.s.sent to Berkeley"s scheme for the Bermuda University only because he thought the House of Commons was sure to throw it out.]
Hardly any epoch in the intellectual history of England is more remarkable in itself, or possesses a greater interest for us in these latter days, than that which coincides broadly with the conclusion of the seventeenth and the opening of the eighteenth century.
The political fermentation of the preceding age was gradually working itself out; domestic peace gave men time to think; and the toleration won by the party of which Locke was the spokesman, permitted a freedom of speech and of writing such as has rarely been exceeded in later times.
Fostered by these circ.u.mstances, the great faculty for physical and metaphysical inquiry, with which the people of our race are naturally endowed, developed itself vigorously; and at least two of its products have had a profound and a permanent influence upon the subsequent course of thought in the world. The one of these was English Freethinking; the other, the Theory of Gravitation.
Looking back to the origin of the intellectual impulses of which these were the results, we are led to Herbert, to Hobbes, to Bacon; and to one who stands in advance of all these, as the most typical man of his time--Descartes. It is the Cartesian doubt--the maxim that a.s.sent may properly be given to no propositions but such as are perfectly clear and distinct--which, becoming incarnate, so to speak, in the Englishmen, Anthony Collins, Toland, Tindal, Woolston, and in the wonderful Frenchman, Pierre Bayle, reached its final term in Hume.
And, on the other hand, although the theory of Gravitation set aside the Cartesian vortices--yet the spirit of the "Principes de Philosophie" attained its apotheosis when Newton demonstrated all the host of heaven to be but the elements of a vast mechanism, regulated by the same laws as those which govern the falling of a stone to the ground. There is a pa.s.sage in the preface to the first edition of the "Principia" which shows that Newton was penetrated, as completely as Descartes, with the belief that all the phenomena of nature are expressible in terms of matter and motion.
"Would that the rest of the phenomena of nature could be deduced by a like kind of reasoning from mechanical principles. For many circ.u.mstances lead me to suspect that all these phenomena may depend upon certain forces, in virtue of which the particles of bodies, by causes not yet known, are either mutually impelled against one another and cohere into regular figures, or repel and recede from one another; which forces being unknown, philosophers have as yet explored nature in vain. But I hope that, either by this method of philosophizing, or by some other and better, the principles here laid down may throw some light upon the matter."[1]
[Footnote 1: "Utinam caetera naturae phaenomena ex principiis mechanicis, eodem argumentandi genere, derivare licet. Nam multa me movent, ut nonnihil suspicer ca omnia ex viribus quibusdam pendere posse, quibus corporum particulae, per causas nondum cognitas, vel in se mutuo impelluntur et secundum figuras regulares cohaerent vel ab invicem fugantur et reced ent: quibus viribus ignotis, Philosophi hactenus Naturam frustra tentarunt. Spero autem quod vel huic philosophandi modo, vel veriori, alicui, principia hic posita lucem aliquam praebebunt."--Preface to First Edition of _Principia_, May 8, 1686.]
But the doctrine that all the phenomena of nature are resolvable into mechanism is what people have agreed to call "materialism;" and when Locke and Collins maintained that matter may possibly be able to think, and Newton himself could compare infinite s.p.a.ce to the sensorium of the Deity, it was not wonderful that the English philosophers should be attacked as they were by Leibnitz in the famous letter to the Princess of Wales, which gave rise to his correspondence with Clarke.[1]
[Footnote 1: "Collection of Papers which pa.s.sed between the late learned Mr. Leibnitz and Dr. Clarke."--1717.]
"1. Natural religion itself seems to decay [in England] very much.
Many will have human souls to be material; others make G.o.d Himself a corporeal Being.
"2. Mr. Locke and his followers are uncertain, at least, whether the soul be not material and naturally perishable.
"3. Sir Isaac Newton says that s.p.a.ce is an organ which G.o.d makes use of to perceive things by. But if G.o.d stands in need of any organ to perceive things by, it will follow that they do not depend altogether upon Him, nor were produced by Him.
"4. Sir Isaac Newton and his followers have also a very odd opinion concerning the work of G.o.d. According to their doctrine, G.o.d Almighty wants to wind up His watch from time to time; otherwise it would cease to move.[1] He had not, it seems, sufficient foresight to make it a perpetual motion. Nay, the machine of G.o.d"s making is so imperfect, according to these gentlemen, that He is obliged to clean it now and then by an extraordinary concourse, and even to mend it as a clockmaker mends his work."
[Footnote 1: Goethe seems to have had this saying of Leibnitz in his mind when he wrote his famous lines--
"Was war" ein Gott der nur von aussen stiesse Im Kreis das All am Finger laufen liesse."]
It is beside the mark, at present, to inquire how far Leibnitz paints a true picture, and how far he is guilty of a spiteful caricature of Newton"s views in these pa.s.sages; and whether the beliefs which Locke is known to have entertained are consistent with the conclusions which may logically be drawn from some parts of his works. It is undeniable that English philosophy in Leibnitz"s time had the general character which he ascribes to it. The phenomena of nature were held to be resolvable into the attractions and the repulsions of particles of matter; all knowledge was attained through the senses; the mind antecedent to experience was a _tabula rasa_. In other words, at the commencement of the eighteenth century, the character of speculative thought in England was essentially sceptical, critical, and materialistic. Why "materialism" should be more inconsistent with the existence of a Deity, the freedom of the will, or the immortality of the soul, or with any actual or possible system of theology, than "idealism," I must declare myself at a loss to divine. But in the year 1700 all the world appears to have been agreed, Tertullian notwithstanding, that materialism necessarily leads to very dreadful consequences. And it was thought that it conduced to the interests of religion and morality to attack the materialists with all the weapons that came to hand. Perhaps the most interesting controversy which arose out of these questions is the wonderful triangular duel between Dodwell, Clarke, and Anthony Collins, concerning the materiality of the soul, and--what all the disputants considered to be the necessary consequence of its materiality--its natural mortality. I do not think that anyone can read the letters which pa.s.sed between Clarke and Collins, without admitting that Collins, who writes with wonderful power and closeness of reasoning, has by far the best of the argument, so far as the possible materiality of the soul goes; and that, in this battle, the Goliath of Freethinking overcame the champion of what was considered Orthodoxy.
But in Dublin, all this while, there was a little David practising his youthful strength upon the intellectual lions and bears of Trinity College. This was George Berkeley, who was destined to give the same kind of development to the idealistic side of Descartes" philosophy, that the Freethinkers had given to its sceptical side, and the Newtonians to its mechanical side.
Berkeley faced the problem boldly. He said to the materialists: "You tell me that all the phenomena of nature are resolvable into matter and its affections. I a.s.sent to your statement, and now I put to you the further question, "What is matter?" In answering this question you shall be bound by your own conditions; and I demand, in the terms of the Cartesian axiom, that in turn you give your a.s.sent only to such conclusions as are perfectly clear and obvious."
It is this great argument which is worked out in the "Treatise concerning the Principles of Human Knowledge," and in those "Dialogues between Hylas and Philonous," which rank among the most exquisite examples of English style, as well as among the subtlest of metaphysical writings; and the final conclusion of which is summed up in a pa.s.sage remarkable alike for literary beauty and for calm audacity of statement.
"Some truths there are so near and obvious to the mind that a man need only open his eyes to see them. Such I take this important one to be, viz., that all the choir of heaven and furniture of the earth--in a word, all those bodies which compose the mighty frame of the world--have not any substance without a mind; that their being is to be perceived or known; that consequently, so long as they are not actually perceived by me, or do not exist in my mind or that of any other created spirit, they must either have no existence at all or else subsist in the mind of some eternal spirit; it being perfectly unintelligible, and involving all the absurdity of abstraction, to attribute to any single part of them an existence independent of a spirit."[1]
[Footnote 1: "Treatise concerning the Principles of Human Knowledge,"
Part I. -- 6.]