the same process apparently begins again. There is thus an important difference between the primary formed and the secondary zooids, which Agassiz does not refer to, viz., that the former are more particularly the result of fission, while the latter are the result of both gemmation and fission. The former would come under Professor Huxley's first category, the latter under his third. We suspect in the proliferous development of the higher Annelids such will always be the case, and that there will always be a combination of two of these categories in their development.

It is interesting to observe that the earlier stages of this Autolytus closely resemble those of a Planarian worm. So remarkably is this the case, that this stage might well be called the Planarian stage. Then in their onward development they resemble some of the genera of Annelids that we have long been in the habit of considering adult forms, such as Leucodore and others-this state reminds A. Agassiz of the Nematoid worms, but this resemblance is not sufficiently evident to us-in their last stage they have become genuine Annelids. Hence it follows that for the future one must be very cautious in defining new species and genera of Annelids, unless their life history is known; otherwise the parent stocks and the sexes of the one species might be referred to three very different species not to say genera.

This paper of Mr. A. Agassiz is illustrated with three excellent plates, which give full details of the development and appearance of the parent stock in Autolytus cornutus and of its male and female zooids. It proves that the son is following well and worthily in his father's footsteps, and we trust we may yet have to notice many papers on this confessedly difficult group of animals from his pen, even though we cannot expect them all to be as startling in their details as this present one.

XXXII.-HERBERT SPENCER'S BIOLOGY.

THE PRINCIPLES OF BIOLOGY. PART IV. MORPHOLOGICAL DEVELOPMENT. Caps. ii. et iii. THE MORPHOLOGICAL COMPOSITION OF PLANTS. By Herbert Spencer. London: 1865.

MR. HERBERT SPENCER, as is known to most of our readers, is engaged in the publication of a system of Philosophy. Several sections of this great undertaking have already been issued, but our

present task concerns the most recent of his publications, the title of which is prefixed to the present article.

Some objections may, doubtless, be raised to this mode of treating a subject in separate parts; but it is one imposed upon us by the necessities of the case, no less than by Mr. Spencer's method of publication. Naturalists in general are so accustomed to think and work inductively that it will be, if not absolutely novel, at least very interesting, to see their subject handled deductively. Not that Mr. Spencer proceeds wholly on the deductive plan, such a course would be plainly impracticable; the method he prefers as likely to conduce to both brevity and clearness is " to establish each general truth empirically, and then proceed to the rationale of it."

The reader, indeed, in perusing this brochure will often be forcibly reminded of the famous "camel" story, and will regret that the author did not make more use of his observant faculties, and trust less to his inner consciousness.. Albeit everything that owes its origin to Mr. Spencer's thought is well worthy perusal and reflection. We shall, therefore, now attempt to lay before our readers an analysis of the views held by this eminent thinker on Vegetable Morphology, and shall add such comments as, in our judgment, we may think desirable. Our task is not an easy one, for the style of writing no less than the mode of thought manifested in this work, is different from those in use among Naturalists generally.

The plant is its own architect, and not only its own architect, but it forms the materials for the edifice to be raised; that edifice is raised according to a certain plan, handed down from generation to generation, and never entirely departed from, though continually modified to meet varied, often conflicting, requirements. A living plant, then, it will be conceded, is made up of a number of units. By the mere increase in number and aggregation of such units the plant grows and increases in bulk, and not only in bulk but in shape, so that its form is changed. The plant, in fact, grows and it is developed.

The Morphologist has thus to study the various ways in which mere increase of bulk takes place, and must also inquire into the shape of the organism as a whole; he must ascertain how, and why, it assumes that shape, how and why its shape differs from that of allied organisms. Thus, at the very outset, is necessitated an inquiry into the nature of the component units, and an investigation of the influences which cause those units to increase in one way

rather than another, and to assume certain forms in some instances, certain other forms in other cases. On the latter points Mr. Spencer does not dilate; he merely states that the factors bringing about the changes of form in plants are external, incident forces, or internal, hereditary proclivities, so that "every organism is the result of a compromise between internal forces tending to reproduce ancestral forms, which were in harmony with incident forces at the time of their evolution, and external incident forces tending to cause deviations from that form."

The two processes of growth and development, and the agencies influencing them, being thus alluded to, our author then proceeds to seek for the physiological units out of which the organisms are to be built. These are specks of protoplasm manifesting life, and yet showing no sign of organization. Organic evolution begins by the formation of a minute aggregate of them into a cell. We may expect "that as structureless portions of protoplasm must have preceded cells in the process of general evolution, so, in the special evolution of each higher organism, there will be an habitual production of cells out of structureless blastema;" and moreover, "that tissue may occasionally be formed by the direct transformation of the blastema." We regret that Mr. Spencer has not pursued this portion of his subject further, and shown us what tissue he expects to be so formed, where to look for it, how to recognize it. Is it the structureless cuticular layer overlying the epidermis of flowering plants, or the gelatinous envelope of such plants as Palmella, or the membrane lining the air-canals of Victoria? But on this point we are left in the dark. The void is in part supplied by the writings of Drs. Lionel Beale and Hughes Bennett on organic molecules, and on the structure and growth of cells.

A cell, then, is an aggregate of the first order, formed of physiological units united into a group, that is structurally single, and cannot be divided without destruction of its individuality. Of such cells we have numerous examples in the lower Algae, Fungi, &c., the cells being sometimes of considerable size and much branched. Aggregates of the second order are plants composed of more than one cell, the cells being sometimes held together by a matrix of mucus, and aggregated in one plane, either in linear series, or radiating from a centre. In other cases they may be grouped on all sides of a central point, aud so form a spherical mass. It is not necessary to follow Mr. Spencer in his review of the filamentous,

tubular, pseudo-foliar, and pseudo-axial Thallogens, as the general features of their composition are well known.

Caulerpa might have found a place in Mr. Spencer's digest as having, though strictly a unicellular plant, a creeping stem, so to speak, growing indefinitely and giving origin to two kinds of branches of limited growth, viz.: roots on one side, leaf-like branches on the other.*

Lessonia, though merely an aggregate of the second order, has a pseudo-foliar and pseudo-axial appearance. In Rhodymenia, Phyllophora, and Delesseria, there are successive stages in gradually increasing complexity. In the last-named beautiful sea-weed there are small fronds springing from the mid-rib of the parent frond, and completely resembling it, except in size. This tertiary degree of composition is yet more fully shown in Sargassum.

In passing from Alge to Jungermanniæ, Mr. Spencer calls attention to the widely different circumstances under which terrestrial plants are placed, as compared with aquatic ones, and the consequent modifications in their mode of growth. The Jungermannicæ exhibit transitional forms from aggregates of the second order to those of the third order, till at length the more perfect of them have an erect stem with separate leaves, and a single root or group of roots; so that the leaves are now not able of themselves to carry on their functions, but depend one on another, and on the other organs, and in this way make up a compound individual.

Having thus dealt with flowerless plants, Mr. Spencer proceeds to the consideration of the morphological constitution of flowering plants, in which there is always aggregation of the third order, and very frequently aggregations of the fourth, fifth, or sixth orders, Mr. Spencer here using the word aggregations in the same sense as Alexander Braun does, when speaking of the "generations" of shoots, &c.

In speaking of the promulgation of the doctrine of metamorphosis, the principal merit is assigned justly to Wolff, for although Goethe arrived at his conclusions independently, and by a partially different road," he is only entitled to a secondary place among those who have established this important generalization." The consideration of this subject leads Mr. Spencer to ask the important questions, "What is a foliar organ, and what is an axial organ ?"

* Decaisne Plantes de l'Arabie heureuse. Arch. du Mus. ii. 1839. t. vi. B.

and, in replying to the question he expresses his conviction that the distinction between the two organs is not absolute. In this we heartily concur; but we regret that the arguments here brought forward in support of this opinion are based upon false premises. For instance, Mr. Spencer speaks of a sepal being transformed into a flower-bud, forgetting the morphological axiom that an organ once formed, never becomes transformed into anything else.

The greatest stress is laid upon the appearances presented by certain monstrous umbellifers. The descriptions of these given by our author are so much at variance with the teaching and dicta of Botanists generally, that it is to be regretted that they are not accompanied by larger and clearer illustrations, in the absence of which no morphologist, we are confident, will accept Mr. Spencer's interpretations. So far as we can judge, we should suppose the malformations in question to have been cases of prolification, either of the inflorescence or of the flower. That is, either the peduncles or rays of the umbel have been subdivided, so as to increase the compound nature of the umbel, or there has been an adventitious formation of flower buds in the axils of the sepals, or of the petals, &c.—axillary prolification in short. These changes have been accompanied by others of more or less importance. Finding an umbellule where, under ordinary circumstances, a single flower is produced, our author's inference is that the flower is transformed into an umbellule. Now, if this were so, then the simple umbel itself would be the result of a transformed flower, and not due to the formation of a second generation of flower-stalks. If Mr. Spencer's views be correct, in what light would he view the bracts of the involucre, or of the involucel? Would they be portions of the flower that is transformed into an umbellule? If so, they should at times, at least, show transitional stages between their ordinary condition and that of floral organs. Proceeding with his descriptions, Mr. Spencer mentions "a peripheral flower, of which one member (apparently a petal, is transformed into a flower bud)." How this could happen we are at a loss to know. Leaf-buds are formed upon leaves under certain circumstances, but there is no instance, that we know of, of a flower-bud actually arising from a leaf-though sometimes, as in Erythrochiton, the adhesion of the flower stalk to the leaf gives rise to such an appearance, but in neither of the cases just cited would any one say that the leaf or flower-bud had arisen from a transformation of the leaf. Other flowers are described as half-flower, half-umbellule; these, then,